Engineering Services, Inc.
Porsche Engineering Services, Inc.
ULSAB Program Phase 2
Final Report
to the
Ultra Light Steel Auto Body
Consortium
Engineering Services, Inc.
Ultra Light Steel Auto Body
Member Companies
Aceralia
AK Steel
Bethlehem
BHP Steel
British Steel
Cockerill Sambre
CSN
Dofasco
Hoogovens
Inland
Kawasaki Steel
Kobe
Krakatau
Krupp Hoesch
LTV Steel
National Steel
Nippon Steel
NKK
POSCO
Preussag
Rouge Steel
SIDERAR
SIDMAR
SOLLAC
SSAB
Stelco
Sumitomo
Tata
Thyssen
US Steel Group
USIMINAS
VSZ
VOEST-ALPINE
WCI
Weirton
Engineering Services, Inc.
ULSAB Final Report Table of Contents
Preface
1. Executive Summary
2. Phase 2 Introduction
2.1.
2.2.
2.3.
2.4.
2.5.
2.6.
2.7.
Phase 2 Program Goal
Phase 2 Design and Analysis
Demonstration Hardware (DH)
Scope of Work
Materials
Testing of Test Unit
Phase 2 Program Timing
3. ULSAB Phase 2 Package
3.1. General Approach
3.2. Package Definition
3.2.1. Vehicle Concept Type
3.2.2. Exterior Dimensions
3.2.3. Interior Dimensions
3.2.4. Main Component Definition
3.2.5. Underfloor Clearance
3.2.6. Seating Position
3.2.7. Visibility Study
3.2.7.1. Horizontal and Vertical Obstruction
3.2.7.2. A-Pillar Obstruction
3.2.8. Gear Shift Lever Position
3.2.9. Pedal Position
3.2.10. Bumper Height Definition
3.3. Package Drawings
Table of Contents - Page 1
Engineering Services, Inc.
4. Styling
4.1. Approach
4.2. 2-D Styling Phase
4.2.1. Sketching
4.2.2. Clinic
4.2.3. Electronic Paint
4.2.4. Styling Theme Selection
4.3. 3-D Styling Model
4.3.1. Surface Release
4.4. Rendering
5. Design and Engineering
5.1. Phase 2 Design and Engineering Approach
5.2. Design and Engineering Process
5.3. ULSAB Phase 2 Design Description
5.3.1. Parts List – Demonstration Hardware
5.3.2. ULSAB Structure Mass
5.3.3. ULSAB Demonstration Hardware Mass
5.3.4. Mass of Brackets and Reinforcements – Phase 2
5.3.5. ULSAB Structure Mass Comparison Phase 1 – Phase 2
5.3.6. DH Part Manufacturing Processes
5.3.7. Material Grades
5.3.8. Material Thickness
5.4. Detail Design
5.4.1. Weld Flange Standards
5.4.1.1. Weld Flanges for Spot or Laser Welding
5.4.1.2. Scalloped Spot Weld Flanges
5.4.1.3. Locator, Tooling and Electrophoresis Holes
5.4.2. Design Refinement
Table of Contents - Page 2
Engineering Services, Inc.
6. CAE Analysis Results
6.1. Selected Tests for CAE
6.2. Static and Dynamic Stiffness
6.2.1. Torsional Stiffness
6.2.2. Bending Stiffness
6.2.3. Normal Modes
6.3. Crash Analysis
6.3.1. AMS Offset Crash
6.3.2. NCAP 100% Frontal Crash
6.3.3. Rear Crash
6.3.4. Side Impact Analysis
6.3.5. Roof Crush (FMVSS 216)
6.4. CAE Analysis Summary
7. Materials and Processes
7.1. Material Selection
7.1.1. Material Selection Process
7.1.2. Definition of Strength Levels
7.1.3. Supplier Selection
7.2. Material Specifications
7.2.1. General Specifications
7.2.2. Material Classes
7.2.2.1.
7.2.2.2.
7.2.2.3.
7.2.2.4.
7.2.3.
7.3. Tailor
7.3.1.
7.3.2.
7.3.3.
Mild Steel Definition
High Strength Steel Definition
Ultra High Strength Steel Definition
Sandwich Material Definition
Material Documentation
Welded Blanks
Selection of Welding Process
Weld Line Layout
Production Blank Layout
Table of Contents - Page 3
Engineering Services, Inc.
7.4. Hydroforming
7.4.1. General Process Description
7.4.2. Benefit for the Project
7.4.3. Forming Simulation (Review)
7.4.4. Tube Manufacturing
7.4.5. Process Steps for Rail Side Roof
7.4.6. Results
7.5. Hydromechanical Sheet Forming
7.5.1. General Process Description
7.5.2. Benefit for the Project
7.5.3. Process Limitations
7.5.4. Results
8. Parts Manufacturing
8.1.
8.2.
8.3.
8.4.
Supplier Selection
Simultaneous Engineering
Part Manufacturing Feasibility
Quality Criteria
9. DH Build
9.1. Introduction
9.2. Joining Technologies
9.2.1. Laser Welding
9.2.2. Spot Welding
9.2.3. Active Gas Metal Arc Welding (MAG)
9.2.4. Adhesive Bonding
9.3. Flexible Modular Assembly Fixture System
9.4. Design of Assembly Fixtures
9.5. DH Build
9.5.1. Assembly Team
9.5.2. Build of the Test Unit
9.5.3. Build of DH #2 to DH #13
Table of Contents - Page 4
Engineering Services, Inc.
9.6. Quality
9.6.1. Body Quality Control Team
9.6.2. Quality Control Measurements of DHs
9.7. Conclusion
10. Testing and Results
10.1. Scope of Work
10.2. Targets
10.3. Static Rigidity
10.3.1. Test Setup
10.3.1.1. General
10.3.1.2. Static Torsion
10.3.1.3. Static Bending
10.3.2. Results
10.3.2.1. Static Torsion
10.3.2.2. Static Bending
10.4. Modal Analysis
10.4.1. Test Setup
10.4.2. Results
10.5. Masses in Test Configuration
10.6. Summary
11. Economic Analysis
11.1. Introduction
11.2. The Process of Cost Estimation
11.2.1. Overview
11.2.2. Cost Model Algorithm Development
11.2.3. General Inputs
11.2.4. Fabrication Input
11.2.5. Assembly Input
11.3. Cost Model Description
Table of Contents - Page 5
Engineering Services, Inc.
11.4. ULSAB Cost Results
11.4.1. Overall Cost Results
11.4.2. Cost Breakdown for Fabrication
11.4.3. Cost Breakdown for Assembly
11.4.4. Cost Analysis for New Technologies and Materials
11.4.5. Sensitivity Analysis
11.5. Body Structure – Comparative Study
11.5.1. Overview
11.5.2. Assumptions
11.5.3. Overall Results
11.6. Conclusion
NOTE: The cost models may be found on the Porsche ULSAB
Phase 2 CD ROM Version 1.0.2.
12. Summary of Phase 2 Results
ULSAB Final Report Appendix Table of Contents
NOTE:
The following information is located on the
Porsche ULSAB Phase 2 CD ROM Version 1.0.2.
1. Parts Book
1.1.
1.2.
1.3.
1.4.
1.5.
Exploded View
Index – Parts Book Sheets
Parts Book Sheets
Index – Parts book, Brackets & Reinforcements
Parts Book Sheets – Brackets & Reinforcements
Table of Contents - Page 6
Engineering Services, Inc.
2. Part Drawings
2.1.
2.2.
2.3.
2.4.
Exploded View
Parts List – Sorted by Part Number
Parts List – Sorted by Material Grade
Part Drawings
3. Typical Sections
3.1. Overview Illustration
3.2. Index – Typical Sections
3.3. Typical Section Sheets
4. Assembly
4.1.
4.2.
4.3.
4.4.
4.5.
4.6.
4.7.
Assembly Tree
Index –Weld Assemblies
Weld Assembly Drawings
Assembly Sequence Illustrations
Index – Bolted and / or Bonded Assemblies
Assembly Drawings, Bolted and / or Bonded Parts
Assembly Illustrations – Bolted and / or Bonded Parts
5. Package Drawings
5.1. Side View
5.2. Plan View
5.3. Front & Rear View
6. Economic Analysis
6.1. Assembly System Data
6.2. Stamping Process Sheets
Table of Contents - Page 7
Engineering Services, Inc.
Preface
In 1994, the steel industry, through the Ultra Light Steel Auto Body Consortium
(ULSAB), commissioned Porsche Engineering Services, Inc. (PES) to conduct a
concept phase (Phase 1) of the ULSAB project to determine if a substantially lighter
steel body structure could be designed.
In September 1995, worldwide auto industry attention was focused on the study
when the results of Phase 1 were announced. The results also affected the growth
of the ULSAB Consortium to 35 member steel companies, representing 18 nations
worldwide.
Encouraged by the results of Phase 1, the ULSAB Consortium once again
commissioned PES to continue with Phase 2, the validation of the Phase 1
concepts, culminating in the build of the demonstration hardware. Phase 2 proved
that the weight reduction, predicted in Phase 1, could be achieved. The use of high
strength steels, tailor welded blanks, hydroforming and laser welding in assembly
were particular challenges to overcome in Phase 2. ULSAB Consortium members
committed themselves to supplying all steel materials, as well as the tailor welded
blanks and raw materials for hydroforming, for all parts to be manufactured.
The focus of Phase 2 was the same as in Phase 1, i.e., weight reduction without
compromising safety or structural performance. Without altering the aggressive
targets for mass and structural performance, the safety requirements were
increased in Phase 2 in response to growing industry and government concern for
increased auto safety. It was imperative to keep up with safety requirement
changes that occurred during the course of the program, which ran from spring
1994 to spring 1998. As a result, it was necessary to analyze the ULSAB structure
for offset crash behavior. With this new challenge, and valuable input gathered in
discussions with OEMs during the presentation of Phase 1 findings, PES and the
ULSAB Consortium commenced Phase 2.
Preface - Page 1
Engineering Services, Inc.
Phase 2 ended in Spring 1998 with the debut of the ULSAB demonstration hardware
and will prove the Phase 1 concept to be not only feasible, but that performance
targets will be exceeded by 60% for torsional rigidity, 48% for bending rigidity and
50% for the normal mode frequency. Relative to the benchmark average, mass
reduction remained at 25%, while crash analysis showed excellent results for the
selected crash analysis events, including the offset crash.
As a result of Phase 2, the use of high strength steels in the ULSAB demonstration
hardware structure has now increased to 90% relative to its mass. The trend
toward using high strength steel and new technologies to reduce body structure
mass while improving safety, can be seen already in recently launched cars. The
new Porsche Boxster, for example, uses 30% high strength steel, as well as tailored
blanking, hydroforming and laser welding in assembly.
Cost analysis in Phase 1 was conducted by IBIS Associates under contract to the
ULSAB Consortium. In Phase 2, a more detailed cost analysis study was
conducted, under the supervision of PES with the support of ULSAB consortium
member companies. With the detailed information provided with the concept
validation in Phase 2, a new cost model was created and the cost to produce the
ULSAB structure was analyzed. The results show that it is possible to reduce the
mass of body structures without cost penalty.
Preface - Page 2
Engineering Services, Inc.
1. Executive Summary
Engineering Services, Inc.
1. Executive Summary
Ultra Light Steel Auto Body (ULSAB) Phase 2
Introduction
On behalf of an international Consortium of 35 of the world’s leading sheet-steel
producers from 18 countries, Porsche Engineering Services, Inc. (PES) in Troy,
Michigan, was responsible for the program management, design, engineering, and
the building of the demonstration hardware (DH). In addition, PES conducted the
economic analysis study for the Ultra Light Steel Auto Body (ULSAB) program.
Program Goal
The goal of the ULSAB program was to develop a light-weight body structure design
that is predominantly steel. This goal included:
•
•
•
Providing a significant mass reduction based on a future reference vehicle
Meeting functional and structural performance targets
Providing concepts that will be applicable for future car programs
Program Structure
In order to achieve the above-mentioned goals the program was structured in three
phases:
•
•
•
Phase 1 Concept Development (paper study)
Phase 2 Concept Validation (build of demonstration hardware)
Phase 3 Vehicle Feasibility (total vehicle prototype assembly and
evaluation)
Chapter 1 - Page 1
Engineering Services, Inc.
Phase 1 – Concept
In September 1995, the results of Phase 1 were published. In this phase, the
ULSAB program concentrated on developing design concepts for light-weight body
structures and validating crashworthiness. Based on benchmarking data, the
performance of a future reference vehicle was predicted and the structural
performance targets for the ULSAB structure, excluding doors, rear deck lid, hood
and front fenders were established. Because the ULSAB program focuses on mass
reduction, a much more aggressive target was set for mass than for the other
structural performance targets. These targets were:
Performance
ULSAB
Targets*
Mass
[ 200 kg
Future Reference
Vehicle Prediction
250 kg
Static torsional rigidity
m 13000 Nm/deg
13000 Nm/deg
Static bending rigidity
m 12200 N/mm
12200 N/mm
m 40 Hz
40 Hz
First body structure mode
* All targets were set for body structure with glass, except the target for mass
For the concept validation, the following crash analysis was performed in Phase 1:
•
•
•
•
NCAP, 100% frontal crash at 35 mph
Rear moving barrier crash at 35 mph (FMVSS 301)
EEVC, side impact crash at 50 km/h (with rigid barrier)
Roof crush (FMVSS 216)
The analytical results of Phase 1 were:
Performance
Phase 1 Results*
Mass
Static torsional rigidity
205 kg
19056 Nm/deg
Static bending rigidity
First body structure mode
12529 N/mm
51 Hz
*Structural performance results were calculated with glass; the mass excludes glass
Chapter 1 - Page 2
Engineering Services, Inc.
With the exception of mass, the results exceeded the targets. Mass was calculated at
205 kg and slightly above the aggressive target of 200 kg.
An independent cost study indicated that, based on a North American
manufacturing scenerio, the Phase 1 concept could cost less to produce than
comparable current vehicle structures. This result, based on the relatively low level
of detail of the ULSAB Phase 1 concept, indicated that a light weight structure could
make substantial use of high strength steel, tailor welded blanks, laser welding in
assembly, and hydroforming, and end up in the cost range of structures of similar
size using a more conventional approach at a higher mass.
Phase 2 - Validation
The Phase 1 design concept and its structural and crash performance results
having had a relatively low mass, provided an excellent foundation for Phase 2 of
the ULSAB program. Based on the success of this Phase 1 paper study, and the
positive recognition by OEMs around the world, the ULSAB Consortium
commissioned PES to undertake Phase 2 starting in November 1995.
The overall goal of Phase 2 was the validation of Phase 1 results, culminating in the
build of the ULSAB demonstration hardware structure. The tasks and
responsibilities of Phase 2 for PES, besides the program management, were to
manage the necessary detail design, engineering, crash analysis, material
selection, design optimization for manufacturing, supplier selection for parts and to
assemble, test and deliver the demonstration hardware to the ULSAB Consortium.
In addition, PES was responsible for a detailed cost analysis based on the Phase 2
detailed design.
Chapter 1 - Page 3
Engineering Services, Inc.
Crash Analysis
During the course of the ULSAB program after the start in Spring 1994, the public
demanded increased vehicle safety, and governments reacted with new
requirements for crashworthiness. Therefore, the decision was made prior to the
beginning of Phase 2, to analyze and to design the ULSAB structure for offset
crash. This would enhance the credibility of the results. The AMS (Auto Motor
Sport) 50% offset frontal crash at 55 km/h was considered the most severe test at
that time and would represent the structural requirements an offset crash demands.
This test was then added to the Phase 1 previously selected crash analysis events.
For side impact crash analysis, a deformable barrier was used instead of the rigid
barrier as used in Phase 1.
The following crash analysis was performed in Phase 2:
•
•
•
•
•
AMS, 50% frontal offset crash at 55 km/h
NCAP, 100% frontal crash at 35 mph (FMVSS 208)
Side impact crash at 50 km/h (96/27 EG, with deformable barrier)
Rear moving barrier crash at 35 mph (FMVSS 301)
Roof crush (FMVSS 216)
All crash calculations indicate excellent crash behavior of the ULSAB structure,
even at speeds that exceed federal requirements. The front and rear impacts were
run at 5 mph above the required limit, meaning 36% more energy had to be
absorbed in the frontal impact. The offset crash also confirmed the overall integrity
of the structure. The roof crush analysis validated that the federal standard
requirement was met, partialy due to the hydroformed side roof rail concept design.
Package
At the start of Phase 2, as a result of various discussions with OEMs during the
presentation of Phase 1 results, the ULSAB package was re-examined. In order to
make the results of Phase 2 more credible, the decision was made not to consider
secondary mass savings. This resulted in significant changes in several areas of
the body structure.
Chapter 1 - Page 4
Engineering Services, Inc.
The relatively small engine specified in Phase 1 was replaced by an average size
3-liter V6, necessitating a complete redesign of the front-end structure, including a
revised front suspension layout and subframe design. The rear suspension also
was revised and the rear rails redesigned accordingly. Essentially, the whole
structure was redesigned, from front to rear bumper, but it still maintained the
structure features as developed in Phase I, such as the side roof rail and the
smooth load flow concept of front and rear rails into the rocker.
Styling
Using the revised package and the adjusted body structure design, styling the
ULSAB was the next challenge. Styling became necessary to create the surfaces
for the body side outer panel with its integrated exposed rear quarter panel, the
windshield, the backlight and the roof panel. The styling concept for the
greenhouse had to consider, in order to integrate, the side roof rail, as well as the
overlapping upper door frame concept. This door concept was chosen mainly for
cosmetic reasons; to cover the visible weld seams, in the upper door opening area
of the body side outer panel which were caused by the tailor welded blank design of
the body side outer panel. For the overall styling approach, the decision was made
to create a neutral, not too futuristic or radical, more conservative styling.
Styling was the first major milestone in Phase 2 and was performed entirely by
computer-aided styling (CAS).
Design and Engineering
After the exterior styling was created, the package was then optimized and the
design modified accordingly. The implication of any design change was assessed
by modifying the Phase 1 static analysis model. Design changes resulting as an
outcome of the analysis were then incorporated into the styling and the package.
With the performance targets met, styling and the Phase 2 package were frozen,
and with a more detailed Phase 2 design, a new shell model for the structural
performance analysis was created. Static analysis was then used to optimize the
Chapter 1 - Page 5
Engineering Services, Inc.
Phase 2 design until the requirements were met and new crash analysis models
were built. In the process of design optimization, which included material grade and
thickness selection, both static analysis and crash analysis were performed with
constantly updated models until the targets were met.
Throughout this process, simultaneous engineering provided input from the tool and
part suppliers, as well as from steel manufacturers, to ensure the manufacturing
feasibility of the designed parts. As a result of the simultaneous engineering
process, only minor design and tool changes were needed after the drawings were
released. When the first part set was completed, a workhorse (test unit) was built.
The validation of the test unit lead to further part optimization and, finally, to the
build of demonstration structures.
Suppliers
At the start of the detail design process in Phase 2, suppliers for stamped and
hydroformed parts were selected in order to be included in the simultaneous
engineering process. Among the selection criteria were quality, experience, skills
and location. Supplier flexibility and their willingness to explore new manufacturing
methods, utilizing material grades rarely used in these applications and to “push the
envelope” in the application of tailor welded blanks or in hydroforming technologies,
were as important in the selection process as their cost competitiveness.
Steel Materials
•
Steel Grades
Perhaps the most important factor in meeting the targets for mass and
crash performance is high strength steel. More than 90% of the ULSAB
structure utilizes high strength and ultra high strength steel. High strength
steels are applied where the design is driven by crash and strength
requirements. Ultra high strength steels with yield strength of more than
550 MPa are used for parts to provide additional strength for front and side
impact. High strength and ultra high strength steel material specifications
range from 210 to 800 MPa yield strength with a thickness range from
Chapter 1 - Page 6
Engineering Services, Inc.
0.65 to 2 mm. With the restriction of lower elongation, different forming
characteristics and greater spring back of high strength steels, material
supplier support combined with forming simulations were important factors
in meeting the challenges for the development of manufacturable part
designs.
•
Steel Sandwich Material
The use of steel sandwich material has contributed to considerable mass
savings. The sandwich material is made with a thermoplastic
(polypropylene) core, with a thickness of 0.65 mm and is layered between
two thin steel skins, each with a thickness of 0.14 mm and yield strength of
240 MPa for the spare tire tub and 140 MPa for the dash panel insert. The
steel sandwich shares many of the same processing possibilities of sheet
steel, such as deep drawing, shear cutting, drilling, bonding, and riveting.
However, it cannot be welded. Parts manufactured from steel sandwich
material can be up to 50% lighter than those made of sheet steel with
similar dimensional and functional characteristics. The spare tire tub
made of steel sandwich material is a pre-painted module that is preassembled with the spare tire and repair tools. The module is dropped into
place and bonded to the structure during the final assembly of the vehicle.
Another application of sandwich material is the dash panel insert, which is
bolted and bonded into the body structure, during final vehicle assembly.
Tailor Welded Blanks
Tailor welded blanks enable the engineers to accurately locate the steel within the
part precisely where its attributes are most needed, while at the same time allowing
for the elimination of mass that does not contribute to performance. Other benefits
of tailor welded blanks include the use of fewer parts, dies and joining operations,
as well as improved dimensional accuracy through the reduction of assembly steps.
Nearly half (45%) of the ULSAB demonstration hardware mass consists of parts
manufactured using laser welded tailored blanks.
Chapter 1 - Page 7
Engineering Services, Inc.
The best example of tailor welded blank usage is the body side outer panel. It
employs a fully laser welded tailored blank with different thicknesses and grades of
high strength steel. Careful placement of the seams in the tailor welded blank is
critical in order to minimize mass and facilitate forming. This consideration was
especially important in the body side outer panel because of its complexity and size,
its use of high strength steels and the integration of the rear quarter panel with its
Class A surface requirement. Mass reduction and the elimination of reinforcements
were key goals in the development of this one-piece design. The consolidation of
parts reduced mass and assembly steps.
Hydroforming
•
Tubular Hydroforming
The use of hydroforming should be considered as one of the most
significant manufacturing processes applied in the ULSAB program for part
manufacturing. The hydroformed side roof rail represents a significant
structural member in the ULSAB structure. The side roof rail distributes
loads appearing in the structure during vehicle operation, and in the event
of an impact, distributes loads from the top of the A-pillar along the roof
into B and C-pillar and then into the rear of the structure. The hydroformed
side roof rail reduces the total number of parts and optimizes available
package space. The raw material used to manufacture the side roof rail is
a laser welded, high-strength steel tube 1 mm thick with an outside
diameter of 96 mm and a yield strength of 280 MPa. The design was
optimized and analyzed for feasibility using forming simulation.
•
Hydromechanical Sheet Forming
The use of hydromechanical sheet forming was chosen for the roof panel
for mass reduction reasons. This process provided the opportunity to
manufacture the roof panel at a thinner material thickness and still achieve
a work-hardening effect in the center area, where the degree of stretch is
normally minimal and an increased material thickness is needed to meet
dent resistance requirements. With hydro-mechanical sheet forming, this
Chapter 1 - Page 8
Engineering Services, Inc.
work-hardening effect is achieved by using fluid pressure to pre-stretch the
blanks in the opposite direction towards the punch. This plastic elongation
causes a work-hardening effect in the center area of the blank. In the
second step, the punch forms the panel towards controlled fluid pressure
and because there is no metal-to-metal contact on the outer part surface,
excellent part quality is achieved. The ULSAB roof panel is manufactured
in 0.7 mm high strength steel with a yield strength of 210 MPa.
Tooling
All tools for stamped parts are “soft” tools made of materials such as kirksite and
built to production intent standards. Tools used for hydroforming are “hard” tools
made of steel. In both cases, part manufacturing tolerances and quality standards
were the same as those used in high-volume production.
DH Assembly
•
Joining Technologies
For the final assembly of the ULSAB structure, four types of joining
technologies were applied. Spot welding is used for joining the majority of
parts. Laser welding became necessary to join the hydroformed side roof
rail to its mating parts. In addition, the rails in the front end structure are
laser welded for improved structural performance. Laser welding in body
structure assembly is already being used in mass production by many
OEMs. The active gas metal arc welding (MAG) process, with its
disadvantages, such as slow welding speed and relatively large heat
impact zones, was kept to a minimum and used only in locations with no
weld access for spot or laser welding. Bonding is used to join the sandwich
parts that cannot be spot or laser welded into the structure. For the joining
of the DH, about one-third fewer spot welds and significantly more laser
welding is employed than for conventional body structures.
Chapter 1 - Page 9
Engineering Services, Inc.
•
Assembly Sequence
For the DH build, the assembly sequence uses two stage body side
framing. The assembly sequence includes underbody assembly, body side
assemblies, roof and rear panel assemblies. All DHs were built in a single
build sequence.
•
Assembly Fixtures
To assemble the DH, a modular fixture system was used. The fixtures
were developed in a CAD system and the positions of locator holes were
then incorporated into the parts design.
DH Testing
Testing was performed on the ULSAB test unit structure to validate its structural
performance and mass. Included were tests for static torsion rigidity, static bending
rigidity, modal analysis and mass in various configurations, including some bolt-on
parts. Testing was performed at Porsche’s Research & Development Center in
Weissach, Germany. Physical testing for crash was not part of the ULSAB program
in Phase 2 and may be performed in a possible Phase 3, after the necessary
components are built and/or assembled into the ULSAB structure.
Economic Analysis
With the detailed information created in Phase 2 of the ULSAB program, the costs
of parts and assembly of the body structure were analyzed. Under the management
of a PES’ team, and with support from the ULSAB Consortium members, an
economic analysis group, comprising of analysts from the Massachusetts Institute
of Technology (MIT), IBIS Associates and Classic Design, a detailed cost model
was constructed that includes all aspects of fabrication and assembly. This cost
model will enable the automotive OEMs to calculate ULSAB cost based on their
own manufacturing criteria. Considering that the focus of Phase 2 was on mass
reduction and not on cost savings, the result of this cost analysis is quite
remarkable. It confirms that significant mass reduction of the body structure, in
Chapter 1 - Page 10
Engineering Services, Inc.
comparision to the benchmark vehicle average mass, was achieved with the use of
steel with no cost penalty.
Summary/Conclusion
Throughout Phase 2, timely execution of the program was critical. All parts
designed and released to our suppliers and all tooling and assembly of the first test
unit have been on schedule. With the data acquired from the validation of the first
test unit and subsequent testing, parts were refined and design optimization was
performed. Refined parts were then used to build the demonstration hardware.
Based on the testing of the demonstration hardware, the ULSAB structure shows
Performance*
Mass
Target
Results
[ 200 kg
203 kg
Static torsional rigidity
m 13000 Nm/deg
20800 Nm/deg
Static bending rigidity
m 12200 N/mm
18100 N/mm
m 40 Hz
60 Hz
First body structure mode
*Structural performances are test results with glass. ULSAB structure mass without glass
the following structural performances:
Achieving these results in a timely manner could only be achieved by utilizing the
team approach that involved all parties in the early stages of the ULSAB program.
A close working relationship with the ULSAB Consortium members and the
commitment of our suppliers and their enthusiasm for the program helped to meet
the challenge of manufacturing parts made of steel materials and combinations that
have not been commonly applied previously. This “pioneering spirit” was carried on
by all members of the PES team, including designers and engineers. The ULSAB
program has explored the potential for mass reduction in the body structure using
steel as the chosen material. State-of-the-art manufacturing and joining
technologies, such as laser welding in assembly and hydroforming as well as
commercially available materials, contributed to the success of the ULSAB
program. It proves that steel offers the potential for light weight vehicle design
which contributes to the preservation of resources and the reduction of emissions.
Based on this experience, the steel industry should further intensify its dialogue and
cooperation with OEMs to achieve their common goal of mass reduction of
tomorrow’s vehicles, to protect the environment and to secure mobility of future
generations.
Chapter 1 - Page 11
Engineering Services, Inc.
2. Phase 2 Introduction
Engineering Services, Inc.
2. Phase 2 Introduction
2.1. Phase 2 Program Goal
The program goal of Phase 2 was the validation of Phase 1 results and the build of
demonstration hardware.
Phase 1 was the concept phase and consisted of concept design and analysis. The
design was basic wire frame and surface data, without holes for drainage or locators
for assembly. The Phase 1 analysis, based on the design concept, was meshed in
its basic form to reflect the surfaces of the structure.
2.2. Phase 2 Design and Analysis
The design in Phase 2 was a refinement of the Phase 1 design. It includes surface
data, allowing for production of tools including principal location points (PLP) and
holes for tooling, drainage and weld access. Additionally, refinement of the design
for manufacture and assembly (DFMA) was developed as the final design
progressed, with emphasis on mass production (more than 100,000 units per year).
The intention in Phase 2 was to continue the development of a “generic” structure
that takes into consideration manufacturing and assembly methods. With the
detailed design of the structural components, and assemblies, and with materials
selected, build specifications and the final assembly sequence were established.
Chapter 2 - Page 1
Engineering Services, Inc.
Computer Aided Engineering (CAE) continued in Phase 2 in conjunction with the
refinement of the design. The analysis provided confirmation of the design as well
as structural and crash performance. The CAE analysis in Phase 2 included:
•
•
Finite Element Model Modification
Structural Analysis consisting of:
w Mass
w Static Torsion
w Static Bending
w Modal Analysis
Continuing development of crash simulation concentrates on:
•
•
•
•
•
AMS, 50% frontal offset crash at 55 km/h
NCAP, 100% frontal crash at 35 mph (FMVSS 208)
Side impact crash at 50 km/h (96/27 EG, with deformable barrier)
Rear moving barrier crash at 35 mph (FMVSS 301)
Roof crush (FMVSS 216)
All models were continuously updated to compare Phase 2 and Phase 1 results in
order to maintain the same performance standards.
2.3. Demonstration Hardware (DH)
The term “demonstration hardware” is used to emphasize that the body structure is
not a prototype but a legitimate representation of a production unit. All
demonstration hardware components had to be fully tooled (soft tools for stamping
and hard tools for hydroforming). All demonstration hardware was built in a single
build sequence. The completed structure had to be “clear-coat” painted for
unrestricted view of the build and construction methods.
Chapter 2 - Page 2
Engineering Services, Inc.
2.4. Scope of Work
Porsche Engineering Services, Inc. in Troy, Michigan executed the program. The
DH build, testing and the CAE analysis was performed at the Porsche R & D Center
in Weissach, Germany. To achieve the targets for performance, timing and cost,
the program responsibilities of PES included the following tasks:
•
•
•
•
•
•
•
•
•
Program Management and Planning
Build Management for the Construction of the Demonstration Hardware
Build of Demonstration Hardware
Part Supplier/Manufacturer Evaluation and Selection
Component Structure Design and Engineering
CAE Analysis
Physical Testing of Test Unit
Economic Analysis Study
Final Program Report
2.5. Materials
The ULSAB Consortium member companies provided all material-specific data
required to design, develop and construct the ULSAB body structure in Phase 2. All
materials used to manufacture parts for the DH build were provided to Porsche by
ULSAB Consortium member companies including the tailor welded blanks and raw
material (tubes) for the manufacturing of the hydroform side roof rail. In addition,
the individual ULSAB Consortium member companies supported the program with
data related to material selection and tailor welded blank development, as well as
forming simulation and circle grid analysis on selected parts in order to create a
feasible part design.
Chapter 2 - Page 3
Engineering Services, Inc.
2.6. Testing of Test Unit
Physical testing was undertaken on the test unit to provide data and allow
correlation of the CAE results with regard to:
•
•
•
•
Mass
Static Torsion
Static Bending
Modal Analysis
Physical crash testing was not part of Phase 2. This could be executed in a
possible Phase 3, with the necessary components, such as suspension, powertrain,
and interior available.
2.7. Phase 2 Program Timing
Prior to the start of Phase 2 the program timing was established and the various
tasks assigned.
Based on this timeline the ULSAB Consortium established specific information release
dates to keep
Chapter 2 - Page 4
Engineering Services, Inc.
ULSAB Phase 2 Program Timeline
Task Name
1996
Q4
Q1
Q2
Q3
1997
Q4
Q1
Q2
Q3
Package Refinement
Styling (CAS)
Class A Surfacing
Design & Engineering
Economic Analysis
CAE Analysis
Design Changes
CAE Analysis (Iteration 1)
Design Changes
CAE Analysis (Iteration 2)
Design Changes
CAE Analysis (Iteration 3)
Release Long Lead Items
Tooling
Test Unit Build
Testing
Design Changes
CAE Validation
Tooling Adjustments
DH Build
Chapter 2 - Page 5
1998
Q4
Q1
Q2
Engineering Services, Inc.
3. ULSAB Phase 2
Package
Engineering Services, Inc.
3. ULSAB Phase 2 Package
3.1. General Approach
Discussions with OEMs about Phase 1 findings provided valuable input and
guidance for the more detailed Phase 2 package layout created at the start of
Phase 2. The Phase 2 package was defined as a modification of the Phase 1
package without being too specific so the package findings could apply to more
than one body structure concept. The most important components, space
definitions and dimensions had to be considered by either defining them using
engineering judgment, or by using actual component dimensions. Furthermore,
secondary mass savings were not considered in order to take a more conservative
and more credible approach. This is also reflected in component size and mass, as
well as in the crash mass used for the crash analysis.
3.2. Package Definition
The first step in the package phase was to define the vehicle concept type, exterior
dimensions, interior dimensions and the main components. With these package
definitions, package drawings were revised and structural hard points defined.
3.2.1. Vehicle Concept Type
In Phase 2 the same concept type definition was used as in Phase 1, five
passenger and four door midsize sedan.
Chapter 3 - Page 1
Engineering Services, Inc.
3.2.2. Exterior Dimensions
Ident.*
Definition
Measurements
W101
Tread - front
1560 mm
W102
Tread - rear
1545 mm
W103
W117
Vehicle width
Body width at SgRP - front
1819 mm
1767 mm
L101
Wheelbase
2700 mm
L103
Vehicle length
4714 mm
L104
Overhang - front
940 mm
L105
Overhang - rear
1074 mm
L114
L123
Front wheel centerline to front SgRP
Upper structure length
1447 mm
2631 mm
L125
Cowl point - X coordinate
2016 mm
L126
Front end length
1281 mm
L127
Rear wheel centerline - X coordinate
4295 mm
L128
Front wheel centerline - X coordinate
1595 mm
L129
H101
Rear end length
Vehicle height
654 mm
1453 mm
H106
Angle of approach
14°
H107
Angle of departure
15°
H114
Cowl point to ground
1001 mm
H121
Backlight slope angle
61°
H122
H124
Windshield slope angle
Vision angle to windshield upper DLO
59°
15°
H136
Zero Z plane to ground - front
112 mm
H138
Deck point to ground
1091 mm
H152
Exhaust system to ground
170 mm
H154
Fuel tank to ground
188 mm
H155
Spare tire well to ground
311 mm
*SAE J1100 Revised May 95
Chapter 3 - Page 2
Engineering Services, Inc.
3.2.3. Interior Dimensions
Ident.*
Definition
Measurements
W3
Shoulder room - front
1512 mm
W4
Shoulder room - second
1522 mm
W5
W6
Hip room - front
Hip room - second
1544 mm
1544 mm
W7
Steering wheel center - Y coordinate
350 mm
W9
Steering wheel maximum outside diameter
370 mm
W20
SgRP - front - Y coordinate
350 mm
W25
SgRP - second - Y coordinate
335 mm
W27
W33
Head clearance diagonal - driver
Head clearance diagonal - second
79 mm
83 mm
W35
Head clearance lateral - driver
136 mm
W36
Head clearance lateral - second
132 mm
L7
Steering wheel torso clearance
418 mm
L11
Accelerator heel point to steering wheel center
412 mm
L13
L30
Brake pedal knee clearance
Front of dash - X coordinate
573 mm
1942 mm
L32
SgRP - second to rear wheel centerline
473 mm
L34
Effective leg room - front
1043 mm
L38
Head clearance to windshield garnish - driver
266 mm
L39
Head clearance to backlite garnish
21 mm
L40
L41
Torso (back) angle - front
Torso (back) angle - second
25°
25°
L42
Hip angle - front
93°
L43
Hip angle - second
86°
L44
Knee angle - front
118°
L45
Knee angle - second
88°
L46
L47
Foot angle - front
Foot angle - second
78°
113°
L50
SgRP couple distance
780 mm
L51
Effective leg room - second
894 mm
L52
Brake pedal to accelerator
48 mm
L53
SgRP - front to heel
832 mm
*SAE J1100 Revised May 95
Chapter 3 - Page 3
Engineering Services, Inc.
3.2.3. Interior Dimensions (Cont’d)
Ident.*
Definition
Measurements
H5
SgRP - front to ground
519 mm
H6
SgRP - front to windshield lower DLO
495 mm
H10
H11
SgRP - second to ground
Entrance height - front
529 mm
798 mm
H12
Entrance height - second
810 mm
H13
Steering wheel to centerline of thigh
67 mm
H14
Eyellipse to bottom of inside rearview mirror
40 mm
H17
Accelerator heel point to steering wheel center
645 mm
H18
H25
Steering wheel angle
Belt height - front
23°
446 mm
H26
Interior body height - front at zero Y plane
1011 mm
H27
Interior body height - front at SgRP Y plane
1220 mm
H29
Interior body height - second at SgRP Y plane
1033 mm
H30
SgRP - front to heel
245 mm
H31
H32
SgRP - second to heel
Cushion deflection - front
303 mm
49 mm
H33
Cushion deflection - second
66 mm
H35
Vertical head clearance - driver
75 mm
H36
Head clearance vertical - second
49 mm
H37
Headlining to roof panel - front
7 mm
H38
H40
Headlining to roof panel - second
Steering wheel to accelerator heel point
7 mm
468 mm
*SAE J1100 Revised May 95
Chapter 3 - Page 4
Engineering Services, Inc.
3.2.3. Interior Dimensions (Cont’d)
Ident.*
Definition
Measurements
H41
Minimum head clearance - driver
88 mm
H42
Minimum head clearance - second
21 mm
H49
H50
Eyellipse to top of steering wheel
Upper-body opening to ground - front
17 mm
1317 mm
H51
Upper-body opening to ground - second
1339 mm
H53
D-point - front to heel
137 mm
H54
D-point - center passenger - front to tunnel
105 mm
H55
D-point - center passenger - second to tunnel
43 mm
H56
H57
D-point - front to floor
D-point - second to floor
182 mm
72 mm
H60
D-point to heel point - second
19 mm
H61
Effective head room - front
1019 mm
H63
Effective head room - second
972 mm
H64
SgRP - front to windshield upper DLO
796 mm
H69
H70
Exit height - second
SgRP - front - Z coordinate
743 mm
631 mm
H71
SgRp - second - Z coordinate
641 mm
H75
Effective T-point head room - front
994 mm
H76
Effective T-point head room - second
932 mm
H77
Seatback height - front
868 mm
H78
H94
Seatback height - second
Steering wheel to cushion - minimum
781 mm
223 mm
*SAE J1100 Revised May 95
Chapter 3 - Page 5
Engineering Services, Inc.
3.2.4. Main Component Definition
Component
Engine
Description
Remarks
V6
Average size
~ 3000 ccm
Engine Mounts
Total of 3
2 on top of front rail
1 on subframe
2
Radiator Size
.252 m
Exhaust System
Single routing,
1 catalytic converter,
With single fan
Vol 2.8 catalytic converter
21 ltr. muffler, LHS
1 muffler
Battery L x W x H
280mm x 170mm x 170 mm
LHS front of engine
compartment
Drive Train
Transverse front wheel drive
Transmission
Automatic - manual
G-shift for manual
included in package
Suspension Type, Front
McPherson
Mounted to front subframe
Suspension Type, Rear
Twist beam
With separate spring
Tire Size Front-Rear
195/60R15
Winter tires 185/60R15
Spare Tire
Fuel Tank volume
Space saver
~65 ltr
Tub to fit full size tire
Located under rear seat
Fuel Filler
On RHS
Routing in package
Bumper Front-Rear
Bolt-on
Crash boxes included
Steering
Rack & pinion
Steering rack housing on
Cargo Volume
490 ltr
VDA method with 200 x 100
x 50 mm module
Weld through type
shock absorber
top of crossmember dash
Hinges
Similar to Porsche 911 / Boxster
Head Lamps
Part of front end module
Interior
Front and rear seat concept
In package drawing
Cockpit
Basic concept with I/P beam
In package drawing
Pedals
Unit with integrated
foot-parking-brake
In package drawing
Chapter 3 - Page 6
Engineering Services, Inc.
3.2.5. Underfloor Clearance
The underfloor clearance of a vehicle depends on the vehicle load. The
determination of the underfloor clearance relative to the road surface was crucial for
the body structure design, styling, selection of components and their positioning in
the vehicle structure. Underfloor clearance is defined as the summary of five
different parameters. These are:
•
•
•
•
•
Curb Clearance Front / Rear
Angle of Approach / Departure
Ramp Brakeover Angle
Oil Pan Clearance
Ground Clearance
To define these parameters, three vehicle positions, which then depended on three
specific load cases, needed to be determined. The three load cases applied to the
vehicle were:
•
Curb weight:
The weight of a vehicle equipped for normal driving conditions. This
includes fluids such as coolant, lubricants and a fuel tank filled to a
minimum of 90%. Also included are the spare tire, tool kit, and car
jack.
•
Design weight:
Vehicle curb weight plus the weight of three passengers (68 kg each,
with luggage 7 kg each) with 2 passengers in the front seat and 1
passenger in the rear seat.
•
Gross vehicle weight:
Vehicle curb weight plus maximum payload (5 passengers plus
luggage).
Chapter 3 - Page 7
Engineering Services, Inc.
To determine the vehicle position relative to the road surface under these load
conditions, the vehicle is positioned relative to zero grid Z-plane.
Z
R1
A
R2
B
Ground
X
Figure 3.2.5-1 ULSAB Vehicle Position Relative to Zero Grid Z-Plane
Using the ULSAB data and the weights of the three load cases, the road surface
positions relative to the zero grid Z-plane and to the vehicle were calculated.
ULSAB Data
5
Number of Seats
2700 mm
Wheelbase
Tires
Front
Rear
195/60-R15
195/60-R15
Front
Rear
2.5 bar
2.5 bar
Pressure
Calculation of Road Surface Positions Relative to the Vehicle
Distance from
Static Tire
Load Case
Zero Grid Z-Plane
Radius
A (mm)
B (mm)
R1 (mm)
R2 (mm)
Curb Weight
395
392
301
308
Design Weight
413
417
301
305
Gross Vehicle Weight
415
462
303
300
Chapter 3 - Page 8
Weight
1350 kg
1575 kg
1850 kg
Engineering Services, Inc.
Gross Vehicle Weight
Design Weight
Curb Weight
Figure 3.2.5-2 Road Surface Relative to Vehicle
With the road surface positions relative to the vehicle, the underfloor clearance was
determined.
170 mm
190 mm
Gross Vehicle Weight
Design Weight
Figure 3.2.5-3 Curb Clearance Front/Rear
14º
15º
Design Weight
Figure 3.2.5-4 Angle of Approach/Departure
Chapter 3 - Page 9
Engineering Services, Inc.
14º
Gross Vehicle Weight
Figure 3.2.5-5 Ramp Breakover Angle
185 mm
Design Weight
Figure 3.2.5-6 Oil Pan Clearance
143 m m
Gross Vehicle W eight
Figure 3.2.5-7 Ground Clearance
Chapter 3 - Page 10
Engineering Services, Inc.
3.2.6. Seating Position
At first the 2-D manikins (spelling taken from SAE) were aligned in a comfortable
seating position taking into consideration the angles between joints such as hip,
knee, and foot. When the seating position was defined, verification was made that
the operating parts like steering wheel, gearshift lever and pedal were in reach.
This was important for ergonomic reasons. Two types of 2-D manikins were used:
The small female, 5th percentile with a height of 147.8 cm; and the tall male, 95th
percentile with a height of 185.7 cm. (5th percentile means that 5% of the
population is smaller or equal in size and 95% is taller. 95th percentile means that
95% of the population is smaller or equal in size and 5% is taller.)
For the dash panel layout the tall male 2-D manikin was used because it is more
difficult to reach, since the seat position of the taller person is more rearward than it
is for a shorter person.
Figure 3.2.6-1 Distance to Operating Parts of the 5% Female and the 95% Male
Chapter 3 - Page 11
Engineering Services, Inc.
3.2.7. Visibility Study
3.2.7.1. Horizontal and Vertical Obstruction
For the study of horizontal, vertical and A-pillar obstruction of the driver’s visibility,
the following positions needed to be defined:
•
Seating Reference Point (SgRP)
It was necessary to determine the seating reference point (SgRP) in order
to position the eyellipse (spelling taken from SAE) template and the
eyepoints V1 / V2. For adjustable seats, the SgRP is defined as the hippoint (H-Point) relative to the driving seat in its most rearward position.
The H-point is defined as the pivot center of the torso and thigh center
lines.
Eyepoints V1, V2
Eyellipse
Torso Line
Thigh Centerline
SgR-Point
Accelerator Heel Point
Figure 3.2.7-1 SgRP, Eyellipse, Eyepoints
•
Eyellipse (SAE J941)
The eyellipse is a tool to describe the vision of a driver. The template with
the eyellipse is positioned with its horizontal reference line 635 mm above
the SgRP and with the vertical reference line through the SgRP. Two
types of templates, with two eyellipses, take the different seat track travel
Chapter 3 - Page 12
Engineering Services, Inc.
ranges into consideration. For the ULSAB vehicle, with a seat track travel
of 240 mm, a template for seat track travel of more than 130 mm was
used.
•
Eye Points V1 / V2 (RREG 77/649)
The coordinates of the eye points V1 / V2 relative to the SgRP were
determined by using the following dimensions:
Point
X
Y
Z
V1
68
-5
665
V2
68
-5
589
Using vision lines through the eye points, the following vision areas are described:
Traffic
Light
Visio
n Ang
le min
. 14º
Wiperfie
ld Angle
10º
Transpare
nt Winds cr
een A rea
7º
Through V
1 (77/649/
EWG)
V1
Horizont View Through V1
Steering Wheel Rim Obscuration 1º Through V2 (77/649/EWG)
(77/649/EWG)
4º Through V2
9/EWG)
Unobstr uctedd Vis ion
ugh V2 (77/64
ro
Th
5º
indscreen Area
W
t
en
ar
sp
Tran
V2
Figure 3.2.7-2 Horizontal Vision
Chapter 3 - Page 13
Engineering Services, Inc.
Visio
nA
rea
Visio
n Ar
ea B
A2
0º (
78/3
17 2
17º
.2/E
(78/3
WG
17 2
)
.3/E
WG
)
V1, V2
Y
X
WG)
2.2/E
8/317
)
13º (7
A
WG
a
Are
.3/E
17 2
Vision
/3
8
7
(
17º
ea B
n Ar
Visio
Figure 3.2.7-3 Vertical Vision
3.2.7.2. A-Pillar Obstruction
In order to determine the A-pillar obstruction, points P1 and P2 have to be
determined first. The coordinates for these points related to the SgR-point are:
Point
X
Y
Z
P1
35 mm
-20 mm
627 mm
P2
63 mm
47 mm
627 mm
The ULSAB structure has a seat track travel of 240 mm. Therefore the X-value has
to be corrected by -48 mm.
Since the torso back angle is 25 degrees, no further correction is necessary for the
X-value and Z-value.
The new coordinates for the P-points are:
Point
X
Y
Z
P1
-13 mm
-20 mm
627 mm
P2
+15 mm
47 mm
627 mm
Chapter 3 - Page 14
Engineering Services, Inc.
Y
P2
+15 mm
SgRP
Pm
+47 mm
Horizontal Line
-20 mm
P1
-13 mm
X
Figure 3.2.7.2-4 Distance of the P-Points Relative to the SgR-Point
Two planes are cutting the A-pillar in an angle of 2 and 5 degrees. In the front most
intersection, the horizontal planes S1 and S2 cut the A-pillar (Figure 3.2.7-5).
S1
S2
S1
Pm
S2
2º
627 mm
5º
SgRP
Figure 3.2.7.2-5 Determination of the Sections S1 and S2
Chapter 3 - Page 15
Engineering Services, Inc.
The sections in the plan view are shown in Figure 3.2.7-6.
P2
Pm
V1, V2
P1
S1
S2
Figure 3.2.7-6 Sections S1 and S2 in Plan View
The point P1 is necessary to determine the A-pillar obscuration for the left side (for
a left hand drive vehicle). P2 is necessary for the right side. If P1 fulfills the
requirements, it is not necessary to determine the obscuration for the right A-pillar,
since the right pillar is farther away from the driver.
The template to determine the obstruction is shown in Figure 3.2.7-7.
P1
m
1 04 m
65
mm
E2
E1
er
nn
1I
S
n
c tio
Se
ter
Ou
2
nS
c tio
Se
α
Figure 3.2.7-7 Template for A-Pillar Obstruction
Chapter 3 - Page 16
Engineering Services, Inc.
The point P1 on the template is aligned to the point P1 on the drawing. The line
“Section S2 Outer” is laid tangent to the most outer edge of the A-pillar section (S2),
including trim, door frame and door seal. The second tangent line “Section S1
inner” is laid to the most inner edge of the A-pillar section (S1), including trim, seal
and dot matrix. (Figure 3.2.7-8).
P1
1º
Figure 3.2.7-8 Template in Position
3.2.8. Gear Shift Lever Postion
The position of the gearshift lever depends on the SgRP-position and on the torso
back angle. The position of the gearshift lever in the side view is shown in Figure
3.2.8-1.
220 mm
m
0m
29
340 mm
Figure 3.2.8-1 Distance of Gearshift Lever Relative to SgR-Point
Chapter 3 - Page 17
Engineering Services, Inc.
3.2.9. Pedal Position
98 mm
58 mm
)
ch
59 mm
53 mm
t
Clu
(
)
ke
Bra
mm
50
(
mm
48
3m
20
Seating Reference Point
m
201 mm
53 mm
m
m
89
Figure 3.2.9-2 Pedal Position Rear
Figure 3.2.9-1 Pedal Position Side
3.2.10. Bumper Height Definition
ECE R42 for the bumper height definition requires a pendulum 445 mm above the
curb weight vehicle position and the design weight vehicle position. At the same
time an overlapping of 35 mm of the pendulum to the bumper is required.
C
D
A
B
Figure 3.2.10-1 Pendulum in the Extreme Height Position
Chapter 3 - Page 18
Engineering Services, Inc.
•
•
•
•
A: Lower edge of the pendulum in the most upper level to the curb
weight vehicle position.
B: Upper edge of the pendulum in the most lower level to the design
weight vehicle position.
C: Overlapping of the pendulum to the bumper in extreme high
position.
D: Overlapping of the pendulum to the bumper in extreme low
position.
A
B
C
D
Front
467 mm
431 mm
91 mm
40 mm
Rear
467 mm
402 mm
89 mm
38 mm
Chapter 3 - Page 19
Engineering Services, Inc.
3.3. Package Drawings
Since package drawings are orthographic projections of the vehicle contour in side
view, plan view, front view and rear view, these views include all essential parts of
the interior such as seats, seat position, seating reference point (SgRP), operating
parts and the door openings. To define the interior of the vehicle including the seat
position, visibility, and obstruction by the pillars, roof, hood and deck lid positions
were determined. It was also important to define positions of the steering wheel,
pedals, and gearshift lever. Other criteria were visibility to the instrument panel, and
head clearance to the front, top and side. In the engine compartment, the engine,
gearbox, exhaust system, radiator and battery were used in defining the space for
the structural members of the front body structure. Components such as the fuel
tank with the fuel filler system, the catalytic converter and exhaust system, and
spare tire tub were also included in the package drawings. The package drawings
were the starting point for the Phase 2 design.
Chapter 3 - Page 20
Figure 3.3.1-1 Packing Drawing Side View
3.3.1. Side View
Engineering Services, Inc.
Chapter 3 - Page 21
Figure 3.3.2-1 Package drawing Plan View
3.3.2. Plan View
Engineering Services, Inc.
Chapter 3 - Page 22
Figure 3.3.3-1 Package Drawing Front View
3.3.3. Front and Rear View
Figure 3.3.3-2 Package Drawing Rear View
Engineering Services, Inc.
Chapter 3 - Page 23
Engineering Services, Inc.
4. Styling
Engineering Services, Inc.
4. Styling
4.1 . Approach
The Phase 1 concept design of the ULSAB program did not account for any Class A
surfaces for the outer panels of the structure. To establish Class A surfaces in
Phase 2, a complete styling of the ULSAB vehicle was necessary in order to create
the surfaces of the roof panel, body side outer panel, the back light and the
windshield. Styling also provided the major feature lines for the doors, deck lid,
hood, fender and front and rear bumpers; these were needed for the development of
the mating structural parts. For Phase 2, styling also gave the ULSAB structure a
professional look and provided surfaces for further design studies in the future, i.e.
on hoods, doors, deck lids, etc. The styling was developed electronically using CAS
(computer aided styling), no clay models were used. With support from Porsche’s
styling studio, PES selected A. D. Concepts, a local source, to carry out the
computer aided styling in a simultaneous engineering approach with PES. At the
first team meetings of PES and A. D. Concepts, several elements of the styling
were discussed with a view to creating a 3-dimensional styling model. Using the
package drawings, important criteria such as overall vehicle proportions, vision
lines, bumper locations and proposed cut lines were specified. After the initial
meetings, a clearly defined vehicle architecture had evolved.
4.2. 2-D Styling Phase
4.2.1. Sketching
In a team review of the first sketches, a neutral styling approach was chosen to
ensure the ULSAB styling model would not be too futuristic or radical. Traditional
sketching techniques were used along with the latest electronic paint sketching
software from the Alias|Wavefront company entitled StudioPaint running on Silicon
Graphics High Impact workstations. Many automotive design studios around the
world use this combination of hardware and software. The use of this tool for such
a project increased productivity and enhanced the overall styling presentation with
professionalism and accuracy, producing tighter sketches and more realistic,
achievable styling goals.
Chapter 4 - Page 1
Engineering Services, Inc.
Figure 4.2.1-1 Styling Sketches
Chapter 4 - Page 2
Engineering Services, Inc.
4.2.2. Clinic
In the first clinic, dozens of sketches were reviewed by the design and styling team
to determine which direction the styling would take prior to its presentation to the
ULSAB Consortium. With the best sketches selected, five separate side view
proposals and several different front and rear end treatments were developed.
Figure 4.2.2-1 Side View Proposal
4.2.3. Electronic Paint
In the studio, the CATIA package data was imported into a 3-D conceptual modeling
software, called CDRS, and a side view outline drawing was developed for
sketching purposes. The drawing was imported into StudioPaint and the five, very
disciplined, side view sketch proposals (A-E) along with front and rear end sketch
proposals were developed.
Chapter 4 - Page 3
Engineering Services, Inc.
4.2.4. Styling Theme Selection
The final styling theme selection was made during a meeting of the ULSAB
Consortium’s editorial group, together with PES and A. D. Concepts. In a secret
ballot, the editorial group members from all around the world selected styling
theme A. With the selection of the specific front and rear end treatments for the 3-D
model, the 2-D phase of the ULSAB styling reached its conclusion.
Figure 4.2.4-1 Selected Styling Theme A
Figure 4.2.4-2 Styling Theme B
Chapter 4 - Page 4
Engineering Services, Inc.
Figure 4.2.4-3 Styling Theme C
Figure 4.2.4-4 Styling Theme D
Figure 4.2.4-5 Styling Theme E
Chapter 4 - Page 5
Engineering Services, Inc.
Figure 4.2.4-6 Selected Front View Proposal
Figure 4.2.4-7 Selected Rear View Proposal
Chapter 4 - Page 6
Engineering Services, Inc.
4.3. 3-D Styling Model
To create the 3-D styling model, the package data was imported into CDRS along
with the selected theme drawing and then the first phase of the 3-D model
commenced. Side view lines, created using 2-D spine curves, were developed to
represent the major feature lines of the vehicle. Typical sections at specific X
locations were constructed. This data was reviewed by the design team to verify
the positions of these major curves.
The construction of the greenhouse, (the upper glass and roof surfaces of the
vehicle), was started, transferring preliminary surfaces back and forth between
CDRS and CATIA using an IGES translator. In the following Class A surfacing
using CATIA, only subtle design changes were made to the CDRS surface model
until both the styling and engineering teams were comfortable with the result. The
release of the styling data by the styling team, in IGES file format, marked the first
step in the 3-D modeling phase.
Next, body side lines were constructed and surfaces were created. With the wheel
openings, and the front and rear stance developed, the model started to take shape.
The team developed the best proposal for front and rear door cut lines and this
information was then incorporated into the CDRS styling model.
After the front and rear end surfaces were completed, shaded tile images of the
surface model were used to evaluate the forms. Highlight sections and surface
curvature graphs were used to verify the aesthetic value of the model.
Chapter 4 - Page 7
Engineering Services, Inc.
4.3.1. Surface Release
Prior to the official surface release, the styling was reviewed to establish the exact
location of all cut lines and shut lines. Shaded tile model images, with highlight
reflection lines, were created in CDRS to allow both styling and engineering to
discuss potential areas of concern. With the final release of the IGES surface
model, the 3-D modeling phase was complete.
Figure 4.3.1- 1 Surface Release
4.4. Rendering
After the release of the surface model, the CDRS model was prepared for
rendering. Model colors were selected in texture maps created to enhance the
overall appearance of the photo realistic rendering. Neutral backgrounds and
specific views were selected to create the first ULSAB styling images. To
incorporate subtle engineering changes in the model, the CDRS 3-D models were
revised and additional renderings were created. The models were enhanced further
by the addition of texture maps for items such as license plate and rear window
defrost. The 3-D model was imported back into StudioPaint 3-D to examine styling
changes to the front and rear lamp treatments. These changes were then
incorporated into the CDRS 3-D model and the final renderings completed, which
concluded the styling phase.
Chapter 4 - Page 8
Engineering Services, Inc.
Figure 4.4-1
Figure 4.4-2
Chapter 4 - Page 9
Engineering Services, Inc.
5. Design and Engineering
Engineering Services, Inc.
5. Design and Engineering
5.1. Phase 2 Design and Engineering Approach
After the package was revised and the styling frozen, the challenge in Phase 2 was
to maintain the structural performances, especially the mass, as analyzed in the
Phase 1 concept. Further research into steel sandwich material led to additional
changes in the Phase 2 design. Because of restrictions in size and application of
the material, new design solutions had to be created to compensate for the
advantages in mass reductions using sandwich material as it was applied in
Phase 1. The hydroformed parts were analyzed for manufacturing feasibility using
the detailed design data created in Phase 2. The restrictions of the hydroforming
process, in combination with the refinement of the design, led to different concepts,
design adjustments, and new solutions to achieve the target for mass.
Furthermore, the 50% off-set crash, an additional crash analysis introduced in
Phase 2, significantly influenced the design of parts, the application of steel grades,
the material thicknesses and in particular, the changes to tailor welded blanks.
Every change in the design process also had to be analyzed for its suitability for
assembly and parts manufacturing. The design approach was driven by mass
reduction and created innovative results without allowing initial component cost
consideration to limit options. The design also focused on a production volume of
more than 100,000 units per year.
As well as concentrating on reaching the targets for performance and mass,
importance was also placed on the reduction of assembly steps, the integration of
reinforcements, the use of tailor welded blanks, and the avoidance of metal arc
welding, wherever possible. Using the same design approach in both Phases 1
and 2, it was possible to maintain low mass and high structural performances. The
Phase 1 design concept and approach, the flexibility of the concept and the
potential that it could be adjusted to various design tasks, were challenged in
Phase 2 and ultimately justified.
Chapter 5 - Page 1
Engineering Services, Inc.
5.2. Design and Engineering Process
The design and engineering process used in Phase 2 is shown in the flow chart
(Fig. 5.2-1). All through this process, a simultaneous engineering approach was
taken to find the best solutions to overcome the design and engineering challenges
emerging in Phase 2.
No
No
Start
Phase 1
Package/Concept
Design
Phase 2
Package
Refinement
Create
Styling
Concept
Modify
Package/
Styling / Design
Modify Phase 1
Shell Model
Steel Supplier
& Part Supplier
Input
Modify Design
Material / Thickness
Adjustment
Meets
Static
Targets
Yes
Yes
No
No
Meets
Static/Crash
Targets
Create / Modify
Phase 2
Crash Model
Yes
Yes
No
No
Parts
Feasible
Yes
Yes
Build of
First
Test Unit
Yes
Yes
Meets
Static
Targets
No
No
No
No
Meets
Yes
Static / Crash
Targets
Yes
Create / Modify
Phase 2 Shell
Model
Material / Thickness
Selection,
Design Modification
Build of Final
Demonstration
Hardware
Figure 5.2-1 Design and Engineering Process
Using the Phase 1 package and concept design as the starting point, Phase 2 then
refines the package. This refined Phase 2 package was the basis for the first
styling layout, and in an interactive process, both were adjusted until the
engineering requirements were met. The styling was frozen and the Phase 1 shell
model was adjusted and analyzed using material thickness optimization to achieve
Chapter 5 - Page 2
Engineering Services, Inc.
the mass target while maintaining the structural performance goals. Together with
the selected suppliers and the Material Group of the ULSAB Consortium, the part
design was discussed and the material thicknesses were selected. With this
information, the design was revised and the Phase 2 shell model created, analyzed
and modified until all targets were met. New Phase 2 crash analysis models were
built and after the first analysis, design modifications, material grade and thickness
selection, further crash analyses were performed, until the results were satisfactory.
With the revised design and material selection, the shell model was updated and
the static analysis performed. The crash and static analysis models were
constantly updated as a result of information from tool, part and steel suppliers.
This was repeated until all results were satisfactory. The design was then modified
and the part drawings released to the suppliers. With the first part set delivered, a
test unit was built and the tests following provided the results for static performance
and most importantly for mass. The design was enhanced and material substituted
as needed. The process of shell and crash model modifications and analysis was
performed again to validate the design. After the final design was released to the
suppliers, parts were manufactured and the demonstration hardware built.
Part of this process included regular design review meetings (not shown in the flow
chart) of the design and engineering team as well as design review meetings with
the demonstration hardware build team, engineers and analysts at Porsche R & D
Center in Germany. In these internal PES meetings, technical problems were
discussed and design directions decided in order to prepare for the demonstration
hardware build and meet established deadlines.
Chapter 5 - Page 3
Engineering Services, Inc.
5.3. ULSAB Phase 2 Design Description
Figure 5.3-1 ULSAB Demonstration Hardware
The ULSAB structure went through many adjustments and modifications in its
transition from the Phase 1 concept to its final design stage at the end of Phase 2.
This was due to added crash performance requirements, package issues,
manufacturing processes and material application limitations. The exploded view
(see Fig. 5.3-2) shows the demonstration hardware in the final Phase 2 design
stage with the exception of minor brackets and reinforcements. Bolt-on parts and
components, used in the analysis for crash performance, such as front and rear
bumpers, engine, suspension, subframe, shock tower braces, tunnel bridge and
fenders, are not considered part of the body structure and therefore are not shown
in the exploded view. However, the structure is equipped with important brackets
and reinforcements. Because tailor welded blanks can eliminate reinforcements,
fewer were required. Included in the demonstration hardware, as shown on the
exploded view, are the bolt-on front-end module and the dash-panel insert, including
the brake booster reinforcement.
Chapter 5 - Page 4
Engineering Services, Inc.
5.3.1. Parts List – Demonstration Hardware
The parts list (Fig. 5.3.1-1) corresponds directly with the exploded view of the
demonstration hardware (Fig. 5.3.1-2) and shows the part name and number, the
material grade, and thickness and the mass of the manufactured part. Parts listed
that have two or more material thicknesses and grades indicate that this part is
made from a tailor welded blank. The mass of the parts listed, is taken from actual
manufactured parts, but does not represent an average of all parts manufactured.
Therefore, the mass of the demonstration hardware can vary slightly in comparison
to the listed mass of the total number of parts.
Demonstration Hardware Parts List
Ma te ria l Ma te ria l
Actua l
Gra de T hickne ss
P a rt
(MP a )
(mm)
Ma ss (kg)
P a rt
No
P a rt N a me
001
Assy Reinf Radiator Support Upper
350
1.00
1.613
002
Reinf Front Rail Extension RH
350
1.00
0.485
003
008 A
Reinf Front Rail Extension LH
Assy Rail Front Outer RH
350
350
1.00
1.50
0.489
3.013
(Tailor Welded Blank)
350
1.60
350
2.00
Assy Rail Front Outer LH
(Tailor Welded Blank)
350
350
1.50
1.60
350
2.00
Assy Rail Front Inner RH
350
1.50
350
350
1.60
1.80
350
1.50
350
1.60
B
(Bolted on)
C
009 A
B
C
010 A
B
C
011 A
B
(Tailor Welded Blank)
Assy Rail Front Inner LH
(Tailor Welded Blank)
C
3.037
5.470
5.500
012
Rail Front Extension RH
350
350
1.80
1.40
2.096
013
Rail Front Extension LH
350
1.40
2.061
014
Bracket Roof Rail Mount Low er RH
350
1.20
0.153
015
021
Bracket Roof Rail Mount Low er LH
Panel Dash
350
210
1.20
0.70
0.150
5.830
022
Panel Dash Insert
Sandw ich
0.95
0.875
026
Member Dash Front
600
1.20
2.290
028
032
Panel Cow l Low er
Panel Cow l Upper
210
210
0.70
0.70
1.272
1.374
034
Assy Member Front Floor Support (2-Req'd)
800
0.70
1.290
038
Assy Reinf Floor Front Seat Rear Outer (2-Req'd)
280
0.80
0.120
040
Pan Front Floor
210
0.70
14.650
(Bolted on)
Figure 5.3.1-1
Chapter 5 - Page 5
Engineering Services, Inc.
Demonstration Hardware Parts List (Cont’d)
P a rt
No
P a rt N a me
042 A
Panel Rocker Inner RH
Ma te ria l Ma te ria l
Actua l
Gra de T hickne ss
P a rt
(MP a )
(mm)
Ma ss (kg)
350
1.30
350
1.70
Panel Rocker Inner LH
350
1.30
6.625
045
(Tailor Welded Blank)
Member Rear Suspension
350
280
1.70
0.70
1.344
046 A
Assy Rail Rear Inner RH
350
1.00
5.250
350
1.30
350
350
1.60
1.00
(Tailor Welded Blank)
350
1.30
350
1.60
Assy Rail Rear Outer RH
(Tailor Welded Blank)
350
350
1.00
1.30
350
1.60
350
1.00
350
350
1.30
1.60
B
043 A
B
B
C
047 A
B
(Tailor Welded Blank)
(Tailor Welded Blank)
Assy Rail Rear Inner LH
C
048 A
B
C
049 A
B
C
Assy Rail Rear Outer LH
(Tailor Welded Blank)
(Bonded on)
6.490
5.240
2.527
2.565
050
Panel Spare Tire Tub
Sandw ich
0.96
2.107
055
Member Panel Back
210
0.65
1.305
057
060 A
Panel Back
Panel Body Side Outer RH
140
210
0.65
0.70
2.502
15.780
B
(Tailor Welded Blank)
280
0.90
C
280
1.30
D
E
350
350
1.50
1.70
061 A
Panel Body Side Outer LH
210
0.70
B
(Tailor Welded Blank)
280
0.90
280
350
1.30
1.50
C
D
15.650
350
1.70
062
Panel A-Pillar Inner Low er RH
350
1.00
1.365
063
064
Panel A-Pillar Inner Low er LH
Panel B-Pillar Inner RH
350
350
1.00
1.50
1.375
3.586
065
Panel B-Pillar Inner LH
350
1.50
3.586
066
Reinf B-Pillar Low er (2-Req'd)
350
0.90
0.830
068
069
Panel Wheelhouse Inner RH
Panel Wheelhouse Inner LH
210
210
0.65
0.65
1.931
1.923
Panel Wheelhouse Outer RH
140
0.65
2.116
(Tailor Welded Blank)
210
0.80
Panel Wheelhouse Outer LH
(Tailor Welded Blank)
140
210
0.65
0.80
E
070 A
B
071 A
B
Figure 5.3.1-1
Chapter 5 - Page 6
2.194
Engineering Services, Inc.
Demonstration Hardware Parts List (Cont’d)
Ma te ria l Ma te ria l
Actua l
Gra de T hickne ss
P a rt
(MP a )
(mm)
Ma ss (kg)
P a rt
N o P a rt N a me
072
Rail Side Roof RH
280
1.00
4.700
073
Rail Side Roof LH
280
1.00
4.860
074
075
Panel A-Pillar Inner Upper RH
Panel A-Pillar Inner Upper LH
350
350
1.50
1.50
1.425
1.416
080
Panel Package Tray Upper
210
0.65
1.876
081
Panel Package Tray Low er
210
0.65
1.497
082
083
Support Package Tray RH
Support Package Tray LH
280
280
0.80
0.80
0.084
0.076
085
Panel Roof
210
0.70
8.680
086
Panel Front Header
280
0.70
0.813
087
090
Panel Rear Header
Member Pass Through (2-Req'd)
140
140
0.70
0.65
0.773
0.662
091
Member Kick Up
800
0.70
1.397
094
Reinf Radiator Rail Closeout RH
(Bolted on)
350
1.00
0.567
095
096 A
Reinf Radiator Rail Closeout LH
Panel Skirt RH
(Bolted on)
350
140
1.00
2.00
0.575
3.457
140
1.60
Panel Skirt LH
140
2.00
098
(Tailor Welded Blank)
Panel Gutter Decklid RH
140
140
1.60
0.65
0.434
099
Panel Gutter Decklid LH
140
0.65
0.437
102
Support Panel Rear Header RH
140
0.70
0.098
103
104
Support Panel Rear Header LH
Rail Fender Support Inner RH
140
420
0.70
1.20
0.098
2.712
105
Rail Fender Support Inner LH
420
1.20
2.699
106
Rail Fender Support Outer RH
350
0.90
1.297
107
108
Rail Fender Support Outer LH
Reinf Front Rail RH
350
350
0.90
1.00
1.297
0.838
109
Reinf Front Rail LH
350
1.00
0.830
110
Plate Rear Spring Upper (2-Req'd)
350
2.00
0.526
115
116
Reinf Panel Dash Brake Booster
Assy Bracket Rear Shock Absorber Mount RH
350
350
1.00
2.00
0.464
0.335
117
Assy Bracket Rear Shock Absorber Mount LH
350
2.00
0.339
120
Reinf Floor Front Seat Rear Center
350
1.20
0.250
122
128
Assy Reinf Rear Seat Inner Belt Mount (2-Req'd)
Bracket Member Pass Through Low er (2-Req'd)
350
350
2.00
1.00
0.244
0.056
130
Bracket Member Pass Through Upper Front
350
1.00
0.129
136
Reinf Panel Dash Upper
350
1.00
0.100
140
142
Pan Rear Floor
Assy Reinf Hinge Decklid (2-Req'd)
210
350
0.70
1.50
4.240
0.224
144
Reinf A-Pillar RH
350
1.50
0.229
(Tailor Welded Blank)
B
097 A
B
(Bolted on)
Figure 5.3.1-1
Chapter 5 - Page 7
3.468
Engineering Services, Inc.
Demonstration Hardware Parts List (Cont’d)
Ma te ria l Ma te ria l
Actua l
Gra de T hickne ss
P a rt
(MP a )
(mm)
Ma ss (kg)
P a rt
N o P a rt N a me
145
152
Reinf A-Pillar LH
Bracket Member Pass Through Upper Rear
350
350
1.50
1.00
0.230
0.145
164
Assy Closeout Fender Support Rail RH
350
1.00
0.115
165
Assy Closeout Fender Support Rail LH
350
1.00
0.115
170
171
Reinf Rail Dash RH
Reinf Rail Dash LH
350
350
1.30
1.30
0.309
0.312
172
Assy Reinf Cow l Low er
350
1.00
0.127
455
Assy Hinge Door Upper RH (2-Req'd)
280
-
0.515
456
457
Assy Hinge Door Low er RH (2-Req'd)
Assy Hinge Door Upper LH (2-Req'd)
280
280
-
0.549
0.515
458
Assy Hinge Door Low er LH (2-Req'd)
280
-
0.549
180
Bracket Trailing Arm Mount RH
350
2.00
0.333
181
188
Bracket Trailing Arm Mount LH
Brace Radiator (2-Req'd)
350
350
2.00
0.80
0.341
0.250
190
Assy Reinf Seat Belt Retractor Rear (2-Req'd)
350
1.20
0.104
(Bolted on)
Total Mass of Parts
Figure 5.3.1-1
Chapter 5 - Page 8
196.770
* *
* See Assemblies 455 - 458
* *
* *
* *
Chapter 5 - Page 9
Figure 5.3.1-2 ULSAB Phase 2 Exploded View
Engineering Services, Inc.
Engineering Services, Inc.
5.3.2. ULSAB Structure Mass
For the Phase 1 concept, it was assumed that future average body structures would
contain approximately 12 kg of brackets and reinforcements. This number can vary,
up or down, depending on the type of vehicle, i.e., front or rear wheel drive, and the
package of components. Since the goal of the ULSAB program is to provide
solutions for a generic concept, it was assumed in Phase 1 that the 12 kg for
brackets and reinforcements have to be considered in the calculation for mass to
give the Phase 1 results more credibility. In Phase 1, the ULSAB structure was
calculated with a mass of 193 kg. With the 12 kg for brackets and reinforcements,
the total mass equals 205 kg. In Phase 2, some of the brackets and reinforcements
are already welded into the structure. These are reflected accordingly in the mass
of the demonstration hardware and also included in the parts list. With the
refinement of the Phase 2 package, minor brackets and reinforcements were
designed (but not manufactured) and their mass was calculated to get a more
accurate determination than the general assumption used in Phase 1. These
brackets and reinforcements represent a more generic, than detailed, selection.
The selection was based on package information, chosen components and
engineering judgment. It can be assumed that in a possible Phase 3, the number of
brackets and reinforcements, and their actual mass when manufactured, can be
insignificantly higher or lower. This depends on the final component selection; their
position in the structure and efforts made to minimize their mass. Also included in
the mass calculation are 100 weld studs. This also represents a generic number for
this type of structure and is based on engineering judgment. The calculated mass
of the ULSAB structure (Fig. 5.3.2-1) is the measured mass of the demonstration
hardware parts and the calculated mass of brackets and reinforcements shown in
Fig. 5.3.2-2 and Fig. 5.3.2-3. The ULSAB structure mass in Phase 2 is 203 kg, with
the variation assumed to be +/- 1%. This low variation is due to each part being
manufactured from one coil of steel. The differences in sheet thicknesses between
coils do not apply for the demonstration hardware, but would have to be considered
in mass production.
ULSAB
=
Structure Mass
203.2 kg
Mass of Demonstration
+
Hardware (Parts)
=
196.8 kg
Figure 5.3.2-1 Definition of ULSAB Structure Mass
Chapter 5 - Page 10
Calculated Mass of Brackets
and Reinforcements
+
6.4 kg
Engineering Services, Inc.
Designed Brackets not Manufactured but
Considered Part of the ULSAB Structure
Part No
331
Nam e
Qty
Calc Mass [Kg]
Bracket Exhaust Mount
2
0.060
332/333
Bracket Engine Mount RH/LH
2
0.528
334/335
Bracket Fender Mount Rear RH/LH
2
0.228
Bracket Battery Tray
1
0.412
336
337
Bracket Spare Tire Mount
1
0.089
Bracket Fuel Tank Mount Rear RH/LH
2
0.242
340
Bracket Front Tie Dow n Hook
2
0.236
341
Bracket Rear Tie Dow n Hook
2
0.236
342/343
Bracket Front Jack Support RH/LH
2
0.656
344/345
338/339
Bracket Rear Jack Support RH/LH
2
0.548
346
Bracket Plenum Support Center
1
0.445
N/A
Weld Studs ~ 100
-
0.300
19
3.980
TOTAL
Figure 5.3.2-2
Designed Reinforcements not Manufactured but
Considered Part of the ULSAB Structure
Part No
Nam e
Qty
Calc Mass [Kg]
310
Reinf Hood Hinge Mount
2
0.086
311
Reinf Instrument Panel Beam Mount
2
0.134
312/313
Reinf Sub-Frame Front Mount
2
0.050
314/315
Reinf Sub-Frame Center Mount
2
0.116
316/317
Reinf Sub-Frame Rear Mount
2
0.418
318
Reinf Steering Rack Assembly Mount RH
1
0.032
319
Reinf Steering Rack Assembly Mount LH
1
0.041
320
Reinf Gear Shift Mount
1
0.271
321
Reinf Front Door Lock Striker
2
0.106
322
Reinf Front Door Check Arm
2
0.030
323
Reinf Rear Door Lock Striker
2
0.146
324
Reinf Rear Door Check Arm
2
0.028
325
Reinf Front D-Ring Adjustment
2
0.298
326
Reinf Rear Seat Cushion Mount
2
0.140
327
Reinf Rear Seat Latch
2
0.068
328
Reinf Rear Seat Back Mount Outer
2
0.278
329
Reinf Rear Seat Back Mount Center
1
0.035
330
Reinf Deck Lid Latch
1
0.136
31
2.413
TOTAL
Figure 5.3.2-3
Chapter 5 - Page 11
Engineering Services, Inc.
5.3.3. ULSAB Demonstration Hardware Mass
The mass of the demonstration hardware is 196.770 kg. This reflects the total
amount of the mass of one complete part set, including brackets, reinforcements
and bolt-on parts, as measured.
In Phase 1, nearly all brackets and reinforcements were included in the theoretical
number of 12 kg and only a few were included in the Phase 1 concept design of the
body structure. With the level of detail design in Phase 2 and the refined package,
it was now possible to design and finally manufacture most of these brackets and
reinforcements and weld or bolt them to the demonstration hardware. It was not the
task in Phase 2 of the ULSAB program to design and to manufacture all brackets
and reinforcements and therefore, the approach to concentrate only on the
important ones was taken.
The mass of these manufactured brackets, reinforcements and bolt-on parts is
included in the demonstration hardware mass and listed in the parts list (Fig.
5.3.1-1). The parts are shown on the exploded view (Fig. 5.3.1-2).
For easier identification, the extracted list from the parts list (Fig. 5.3.3-2, -3 to Fig.
5.3.3-4) identifies these parts including their mass.
The mass of the demonstration hardware as shown in Fig 5.3.3-1, consists of the
mass of the pure body structure and the mass of brackets, reinforcements, bolt-on
parts manufactured and welded or assembled to the body structure.
Mass of Brackets,
Reinforcements, Bolt-on Parts,
DH Mass
=
Body Structure Mass
+
Welded and Assembled to
the Body Structure
196.8 kg
=
186.6 kg
+
Figure 5.3.3-1 Demonstration Hardware Mass Definition
Chapter 5 - Page 12
10.2 kg
Engineering Services, Inc.
Reinforcements Manufactured and Welded to Structure
Part No
Nam e
Qty
Mass [Kg]
038
Assy Reinf Floor Front Seat Rear Outer
2
0.120
110
Plate Rear Spring Upper
2
0.526
120
Reinf Floor Front Seat Rear Center
1
0.250
122
Reinf Rear Seat Inner Belt Mount
2
0.244
136
Reinf Panel Dash Upper
1
0.100
142
Assy Reinf Hinge Decklid
2
0.224
144
Reinf A-Pillar RH
1
0.229
145
Reinf A-Pillar LH
1
0.230
164
Assy Closeout Fender Support Rail RH
1
0.115
165
Assy Closeout Fender Support Rail LH
1
0.115
176
Hinge Base RH
4
0.650
177
Hinge Base LH
4
0.650
178
Hinge Stem 119
4
0.379
179
Hinge Stem 141
4
0.449
172
Assy Reinf Cow l Low er
1
0.127
190
Assy Reinf Seat Belt Retractor Rear
2
0.104
33 parts
4.512
Figure 5.3.3-2
Brackets Manufactured and Welded to Structure
Part No
Nam e
Qty
Mass [Kg]
1
0.335
116
Assy Bracket Rear Shock Absorber Mount RH
117
Assy Bracket Rear Shock Absorber Mount LH
1
0.339
180
Bracket Trailing Arm Mount RH
1
0.333
181
Bracket Trailing Arm Mount LH
1
0.341
4 parts
1.348
Figure 5.3.3-3
Bolt-On Parts Manufactured and Attached to Structure
Part No
Nam e
Qty
Mass [Kg]
001
Assembly Reinf Radiator Support Upper
1
1.613
022
Panel Dash Insert
1
0.875
094
Reinf Radiator Rail Closeout RH
1
0.567
095
Reinf Radiator Rail Closeout LH
1
0.575
115
Reinf Panel Dash Brake Booster
1
0.464
188
Brace Radiator
2
0.250
7 parts
4.344
Figure 5.3.3-4
Chapter 5 - Page 13
Engineering Services, Inc.
5.3.4. Mass of Brackets and Reinforcements – Phase 2
The total mass of all brackets and reinforcements, (meaning the calculated mass of
designed, not manufactured parts) and bolted-on parts welded or assembled to the
demonstration hardware, amounts to 16.6 kg, and is included in the ULSAB
structure mass of 203.2 kg.
Total Mass of Brackets, Reinforcements & Bolt-on Parts - 16.6 kg
Calculated mass of brackets &
reinforcements, not manufactured or
part of the ULSAB Structure
Bolt-on parts assembled
to body structure
6.4 kg
4.35 kg
1.35 kg
4.5 kg
Brackets welded to
body structure
Reinforcements welded to
body structure
Figure 5.3.4-1 Mass Breakdown of Brackets, Reinforcements and Bolt-on Parts
Chapter 5 - Page 14
Engineering Services, Inc.
5.3.5. ULSAB Structure Mass Comparison Phase 1 – Phase 2
The comparison of the results of the ULSAB structure mass is shown in Fig.
5.3.5-1. In Phase 2 the measured body structure mass has decreased with the
refinement of the design, compared with the body structure mass as calculated in
Phase 1.
The total calculated mass of 205 kg, as in the Phase 1 ULSAB structure, is
compared to the Phase 2 ULSAB structure mass of 203.2 kg, which includes the
actual mass of the demonstration hardware plus the calculated mass of brackets
and reinforcements.
Phase 1
Assumed theoretical
mass of brackets &
reinforcements
{
Phase 2
6.4 kg
12 kg
}
}
Calculated mass of brackets &
reinforcements designed, not
manufactured
Brackets, reinforcements
& bolt-on parts included in
demonstration hardware (10.2 kg)
Concept
Validation
193 kg
Body
structure
Mass
ULSAB
Structure 205 kg
Mass
+
+
+
+
+
+
196.8 kg
Offset crash
Offset crash
Package refinement
Package refinement
Styling
Styling
Body
Structure
Mass
ULSAB
Structure 203.2 kg
Mass
±1%
Figure 5.3.5-1 ULSAB Structure Mass Phase 1 - Phase 2
Chapter 5 - Page 15
Mass of
Demonstration
Hardware
Engineering Services, Inc.
5.3.6. DH Part Manufacturing Processes
The ULSAB structure as developed during Phase 1 and refined in Phase 2 is in
general, a unibody design, with the exception of the hydroformed side roof rails.
Stamping was the main manufacturing process considered for the parts design.
Relative to the body structure mass of 196.8 kg, 89.2% is the mass of all stamped
parts.
The stampings can be divided into two groups; conventional stampings and
stamped parts made from tailor welded blanks. 42.8% of the body structure mass
is represented by conventionally stamped parts and 44.9% is the mass of parts
made from tailor welded blanks. This relatively high percentage of tailor welded
blank stampings, relative to the body structure mass, is one good indication of how
the mass reduction was achieved. Especially if the use of high strength steels, in
connection with the tailor welded blanks, is put into consideration.
The hydroforming process is applied in the form of two processes:
•
•
The tubular hydroforming process for the side roof rail manufacturing
The hydromechanical sheet forming process, for the roof panel
manufacturing.
The spare tire tub and the dash panel insert are designed to be manufactured from
steel sandwich material, also using the stamping process.
Chapter 5 - Page 16
Engineering Services, Inc.
The mass of the stamped parts made from steel sandwich material is 1.5% relative
to the overall mass. 1.5% are miscellaneous parts, stock materials, such as tubes,
or the forged hinge base of the weld through hinges.
The pie chart in Fig. 5.3.6-1 shows the mass distribution of the manufacturing
processes relative to the DH mass.
The process used to manufacture the parts is shown in Fig. 5.3.6-2.
ÒÒÒ 89.2% Stampings
ÒÒ 9.3% Hydroforming Parts
Ò 1.5% Misc.(Stock Material) Parts
44.9% Tailor Welded Blank Stamping
42.8% Conventional Blank Stamping
1.5% Miscellaneous
1.5% Steel Sandwich
Material Blank Stamping
4.9% Tubular
Hydroforming
4.4% Sheet Hydroforming
Figure 5.3.6-1 Manufacturing Process Relative to DH Mass
Chapter 5 - Page 17
Engineering Services, Inc.
* *
* *
Chapter 5 - Page 18
* *
* *
Part Manufacturing Process
Ò “Conventional Blank”, Stamping
Ò Tailor Welded Blank, Stamping
Ò Sheet, Hydroforming
Ò Tubular Hydroforming
Ò Sandwich Material Blank, Stamping
Ò Misc.(Stock Materials)
* See Assemblies 455 - 458
Figure. 5.3.6-2 ULSAB Manufacturing Processes of Demonstration Hardware Parts
Engineering Services, Inc.
5.3.7. Material Grades
The selection of the steel grades is a result of the need for good crash performance
and mass reduction.
In Phase 2, the utilization of high strength steel is 91%, relative to the DH mass
(Fig. 5.3.7-1) of Phase 1.
The parts design had to consider the lower elongation, and together with the tool
manufacturer, the parts design was optimized to accommodate the different forming
characteristics and greater spring back of high and ultra high strength steels. This
was most important for the design of the tailor welded blank stamped parts which
where different grades and thicknesses of high strength steels and combined into
one part.
High strength and ultra high strength steel material was used on parts contributing
to the crash management of the structure, i.e. front rails, rear rails, rocker, etc. (Fig.
5.3.7-2). With this approach, and in combination with tailor welded blanks, it was
possible to avoid the need for reinforcements and thus reduced the total number of
parts.
For mass reduction, steel sandwich material was applied in the spare tire tub and
the dash panel insert. Steel sandwich material contributes to 1.5% of the DH mass.
Due to the overall design, material specifications of steel sandwich material and
restrictions in its applications, such as low heat resistance and available size, this
material’s use was limited during Phase 2.
Chapter 5 - Page 19
Engineering Services, Inc.
Mild Steel 7.6%
High Strength Steels 90.9%
Steel Sandwich Material 1.5%
45.1% - 350 MPa
13.5% - 280 MPa
27.1% - 210 MPa
2.7% - 420 MPa
7.6% - 140 MPa
1.5% - Steel Sandwich
Material
Figure 5.3.7-1
Chapter 5 - Page 20
2.5% - Ultra High Strength
Steel > 550 MPa
Ò 140 MPa
Ò 210 MPa
Ò 280 MPa
Ò 350 MPa
Ò 420 MPa
Ò > 550 MPa Ultra High Strength Steel
Ò Steel Sandwich Material
* *
* *
* *
* *
Figure. 5.3.7.-2 Material Grades of DH Parts
* See Assemblies 455 - 458
Engineering Services, Inc.
Chapter 5 - Page 21
Ò 140 MPa
Ò 210 MPa
Ò 280 MPa
Ò 350 MPa
Ò 420 MPa
Ò >550 MPa
Ò Steel Sandwich Material
Engineering Services, Inc.
5.3.8. Material Thickness
The distribution of the used material sheet thicknesses relative to the DH mass is
shown in Fig. 5.3.8-1. The majority of the mass (25%) is made from 0.7 mm sheet
steel. Parts with a large surface area such as the panel floor, the panel dash and
the panel roof are manufactured of high strength steel of this thickness, and are
parts with secondary influence in crash performance.
All 1.3 mm thickness material is high strength steel with the yield strength ranging
from 280 MPa (46%) to 350 MPa (54%). The parts made of 1.3 mm material used
in “conventional” stampings and tailor welded blank stampings have primary
influence on crash performance.
Since the demonstration hardware mass consists of 91% high strength steel, nearly
all parts are made from high strength steel sheets in a thickness ranging from
0.65mm to 2.0mm.
Percent Distribution of Material Thickness Relative to DH Mass
25.1%
10.8%
10.9%
9.1%
7.6%
3.0%
4.2%
0.8%
0.65 0.70
2.1%
8.4% 7.6%
3.0%
4.4%
0.80 0.90 1.00 1.20 1.30 1.40 1.50 1.60 1.70 1.80 2.00
Material Thickness
Figure. 5.3.8-1
Chapter 5 - Page 22
1.5% 1.5%
Sandwich Misc
Engineering Services, Inc.
5.4. Detail Design
PES executed an entirely paperless design using Computer Aided Design (CAD)
and CATIA software for the detail design. With the involvement of part suppliers in
the United States and Europe, the Porsche R & D Center, in Germany, and the
necessary data exchange for the tool development and the design of the assembly
fixtures, this approach proved to be very efficient.
5.4.1. Weld Flange Standards
For the detail parts design it was important to define standards for the design of the
weld flanges. The decision was made not to reduce the weld flange width for mass
reduction, which allowed the use of standard weld equipment for the demonstration
hardware assembly.
5.4.1.1. Weld Flanges for Spot or Laser Welding
For the design of parts to be spot welded, the flange length was designed to the
Porsche standards shown in Fig. 5.4.1.1-1.
For the laser welding in assembly, the same standards were applied.
Figure 5.4.1.1-1 ULSAB Spot Weld Standards
Chapter 5 - Page 23
Engineering Services, Inc.
5.4.1.2. Scalloped Spot Weld Flanges
Scalloped flanges were used for mass reduction.
Figure 5.4.1.2-1 Part no. 81 Panel Package Tray Lower with Scalloped Flanges
The design is similar to the scalloped flanges used in production of the Porsche 911
and Boxster. The second reason for scalloping weld flanges was to create two sheet
spot welding where three sheet spot welding would have been applied, otherwise.
Scalloped flanges were applied to parts not critical for sealing and not sensitive to
crash or durability. The mass reduction achieved with scalloped flanges on the
selected parts, based on the calculated part mass equals 0.43 kg. (Fig. 5.4.1.2-4)
The flange geometry is shown in Fig. 5.4.1.2-2. The layout for a two sheet weld
flange and a three sheet weld flange with scalloped flanges is shown in Fig. 5.4.1.2-3.
Chapter 5 - Page 24
Engineering Services, Inc.
Flange Geometry
Figure 5.4.1.2-2 Flange Geometry
Two Sheet Weld Flange
Three Sheet Weld Flange
Figure 5.4.1.2-3 Layout of 2 and 3 Sheet Weld Flanges
Chapter 5 - Page 25
Engineering Services, Inc.
Part
Number
Part Name
Calculated Part Mass Calculated Part Mass with Mass Reduction
[kg]
Scalloped Flange [kg]
[kg]
21
Panel Dash
6.180
6.140
0.040
28
Panel Cowl Lower
1.400
1.326
0.074
40
Pan Front Floor
15.934
15.892
0.042
45
Member Rear Suspension
1.486
1.440
0.046
55
Member Panel Back
1.450
1.424
0.026
68
Panel Wheelhouse Inner RH
2.141
2.110
0.031
69
Panel Wheelhouse Inner LH
2.141
2.110
0.031
81
Panel Package Tray Lower
1.700
1.594
0.106
140
Pan Rear Floor
4.330
4.298
0.032
0.428
Figure. 5.4.1.2-4 Mass Reduction with Scalloped Flanges
5.4.1.3. Locator, Tooling and Electrophoresis Holes
Included in the detail part design are all locator holes for the assembly. All locator
holes needed for parts manufacturing and the holes necessary for the
electrophoresis of the body structure. After the location of the holes for
electrophoreses were first determined, they were then incorporated into the crash
models and the crash analysis was performed to verify that their position did not
have any negative influence on the crash performance. After this verification, the
holes were incorporated into the parts design.
Chapter 5 - Page 26
Engineering Services, Inc.
5.4.2. Design Refinement
Phase 1 reflected a concept design. In Phase 2, the task was to make the design
feasible for manufacturing of the parts to maintain low mass and structural
performances and also, to achieve the crashworthiness of the structure. In the
refinement of the design, changes to the design concept were done for the following
reasons:
•
•
•
•
•
•
•
Mass reduction
Manufacturing and tooling
Assembly
Material specifications
Crash performance
Package
Styling
The overview of design changes as shown in Fig. 5.4.2-1, names the parts or areas
of the structure, the design change and the reason for the different solution or
change from Phase 1 to Phase 2.
Chapter 5 - Page 27
Engineering Services, Inc.
Overview of Major Design Changes in Phase 2
Part
No.
Part / Location
Area
Description
of Change
Reason
for Change
1
Fender Support Rail
Hydroforming part was replaced with
Assembly, part manufacturing
2 part stamping
2
Pan Front & Pan Rear Floor
3 part front floor with sandwich
material tunnel deleted
Heat resistance of sandwich material
not sufficient for bake hardening
process
3
Rear Rails
Spring & shock absorber relocated
with new rear suspension
Mass reduction, package
4
Front Rails
Space between rails increased
Package of bigger engine
Rear part of the front wheelhouse
deleted
Mass reduction
Redesigned, tailor welded blank
Package of new front suspension in
conjunction with #4
5
Panel Skirt
Reinforcement shock tower deleted,
Mass reduction
integrated in new panel skirt
6
Panel Spare Tire
Tub designed as separate module
Heat resistance of sandwich material,
from steel sandwich material and to
not sufficient for bake hardening
be bonded to the rear floor after final
process
assembly
7
Package Tray
Redesigned from 3 part to 2 part
design roll formed member package Assembly
tray front deleted
8
Member Dash Front,
Member Front Floor
Support, Member Kick-up
Material changed from high strength
to ultra high strength steel >550 MPa Front Crash, side impact crash
yield strength
9
Panel Body Side Outer
Blank configuration in tailor welded
blank with all blanks in high strength Crash analysis, mass reduction
steels
10
B-Pillar Joint
Rocker inner extended upwards into
B-Pillar. B-Pillar lower
Side impact, crash assembly
reinforcement modified
11
A-Pillar - Cowl - Fender
Support Rail-Hinge Pillar
Joint
Joint modified
Assembly, revised fender support rail
12
Panel Back
3 Piece design integrated into one
part
Mass reduction, assembly
13
Side Roof Rail
Design refinements
Manufacturing process - hydroforming
14
Bolt on Front End
Welded
Change in front end module concept
Figure 5.4.2-1
Chapter 5 - Page 28
Engineering Services, Inc.
6. CAE Analysis Results
Engineering Services, Inc.
6. CAE Analysis Results
6.1. Selected Tests for CAE
To verify that the ULSAB meets the targets set in the beginning of Phase 1, the
following tests were chosen for the static and dynamic stiffness.
Structural Performances
Targets
Static torsion stiffness
≥ 13000 Nm/deg
Static bending stiffness
≥ 12200 N/mm
Normal modes (first modes)
≥ 40 Hz
Figure 6.1-1 Load cases and targets for static and dynamic stiffness
For analytical crash testing the following tests were selected:
•
•
•
•
•
AMS, 50% frontal offset crash at 55 km/h
NCAP, 100% frontal crash at 35 mph (FMVSS 208)
Side impact crash at 50 km/h (96/27 EG, with deformable barrier)
Rear moving barrier crash at 35 mph (FMVSS 301)
Roof crush (FMVSS 216)
6.2. Static and Dynamic Stiffness
Based on CAD surface data the FE-Model (Figure 6.2-1) for the body in white was
created. Because of the structure symmetry, only a half model with certain
boundary conditions at the symmetry plane at y=0 for the static and dynamic
stiffness simulations were used. The stiffness model consists in triangle and
quadrilateral elements. To connect the different structure components, different
methods were used. To connect laser welded parts in the FE-Model, the nodes of
the flanges were equivalent. For spot welded areas the middle flange nodes are
connected with welding point elements. The weld point distance was with a point
Chapter 6 - Page 1
Engineering Services, Inc.
distance of about 50 mm. The CAE configuration for the static and dynamic
simulations consist of the following parts:
•
•
•
•
•
•
•
•
•
•
Welded Body Structure
Bonded Windshield and Back Light
Bonded and bolted Panel Dash Insert (Part-No. 022)
Bonded Panel Spare Tire Tub (Part-No. 050)
Bolted Reinforcement Panel Dash Brake Booster (Part-No. 115)
Bolted Braces Radiator (Part-No. 188)
Bolted Reinforcement Radiator Rail Closeout RH/LH (Part -No. 094/095)
Bolted Reinforcement Radiator Support Upper (Part-No. 001)
Bolted Tunnel Bridge Lower/Upper
Bolted Brace Cowl to Shock Tower Assembly
Figure 6.2-1 FE-Model
The stiffness model (per half model) consisted of:
•
•
54521 shell elements
53460 nodes
The deformed shapes for the load cases torsion and bending are shown in the
Figures 6.2.1-1 and 6.2.2-1. To view the stiffness distribution vs. the x-axis, the
diagrams 6.2.1-2 (torsion) and 6.2.1-3 (bending) are used. The derivation vs. the
x-axis for torsion (Fig. 6.2.1-3) and bending (Fig.6.2.2-3) as well as the strain
energy contour plots (Fig. 6.2.1-4 and Fig. 6.2.2-4) show the sensitive areas. The
colored areas of the strain plots show the elastic energy, which is a result of the
Chapter 6 - Page 2
Engineering Services, Inc.
deformation stored in the structure, as internal energy. The deformed shape of the
dynamic stiffness simulation, the normal modes are shown in the Figures 6.2.3-1 to
6.2.3-3. The deformed frequency mode belongs to the normal modes mentioned in
Table 6.2-2.
CAE Structural Performance
Static Torsional Stiffness
21310 Nm/deg
Static Bending Stiffness
20540 N/mm
CAE Mass* (with glass)
230.6 kg
CAE Mass* (without glass)
202.8 kg
First Torsion Mode
61.4 Hz
First Bending Mode
61.8 Hz
Front End Lateral
60.3 Hz
*Mass as in test configuration (Chapter 6, page 2), brackets and
reinforcements (6.4 kg) are not included (see Chapter 5, page 10)
Figure 6.2-2 Table of CAE Structural Performance
6.2.1. Torsional Stiffness
A load of 1000 N was applied at the shock tower front while the body structure was
constrained at the rear center spring attachment in the lateral and vertical
directions.
Figure 6.2.1-1 Deformed Shape for Torsion
Chapter 6 - Page 3
Engineering Services, Inc.
21310 Nm/deg
Torsion Angle
0.08
Support
Angle = atan (zdisp/ycoor) [deg]
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0
-0.01
500
1000
1500
2000
2500
3000
3500
4000
Shock Tower
Front
4500
5000
5500
Center, Spring
Attachment Rear
Longitudinal X-axis [mm]
Figure 6.2.1-2 Torsion Angle vs. x-Axis
Derivation of Torsion Angle
0.03
Support
Derivation of Angle [deg/mm]
0.02
0.01
0
-0.01
-0.02
-0.03
-0.04
-0.05
500
1000
1500
2000
Shock Tower
Front
2500
3000
Figure 6.2.1-3 Derivation of Torsion Angle vs. x-Axis
Chapter 6 - Page 4
3500
Longitudinal X-axis [mm]
4000
4500
5000
Center, Spring
Attachment Rear
5500
Engineering Services, Inc.
Figure 6.2.1-4 Strain Energy Contour Plot for Torsion
6.2.2. Bending Stiffness
The loads were applied to the center of the front seats and to the center of the two
outer rear seats. The measurements were taken under a load of F max = 4000 N
b
(4 x 1000 N).
Figure 6.2.2-1 Deformed Shape for Bending
Chapter 6 - Page 5
Engineering Services, Inc.
20540 N/mm
Vertical Z-Displacement
0.25
Support
Vertical Z-Displacement [mm]
0.2
0.15
0.1
0.05
0
-0.05
-0.1
-0.15
-0.2
500
1000
1500
2000
Shock Tower
Front
2500
3000
3500
4000
Longitudinal X-Axis [mm]
4500
5000
5500
Center, Spring
Attachment Rear
Figure 6.2.2-2 z-Displacement vs. x-Axis, Bending
Derivation of Vertical Z-Displacement
Derivation of vertical Z-Displacement [mm]
0.4
Support
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
-0.4
500
1000
1500
Shock Tower
Front
2000
2500
3000
3500
4000
Figure 6.2.2-3 Derivation of z-Displacement vs. x-Axis, Bending
Chapter 6 - Page 6
4500
Longitudinal X-Axis [mm]
Center, Spring
Attachment Rear
5000
5500
Engineering Services, Inc.
Figure 6.2.2-4 Strain Energy Contour Plot for Bending
6.2.3. Normal Modes
Figure 6.2.3-1 Front End Lateral Mode
Chapter 6 - Page 7
Engineering Services, Inc.
Figure 6.2.3-2 First Bending Mode
Figure 6.2.3-3 First Torsion Mode
Chapter 6 - Page 8
Engineering Services, Inc.
6.3. Crash Analysis
For three crash types of the ULSAB project, one common crash model was
generated. With this model the crash simulations were conducted:
•
•
•
AMS 50% frontal offset crash at 55 km/h
NCAP 100% frontal crash FMVSS 208 at 35 mph
Side impact crash at 50 km/h (96/27 EG with deformable barrier)
For the rear crash (FMVSS 301) at 35mph only a half structure (Fig. 6.3.3-1) was
used. Fig. 6.3-1 shows the high level of detail for the FE-Model. To realize a
realistic crash behavior of the simulation, all the spot welds and laser welded areas
were considered in the models. To analyze the crash behavior, all crash-relevant
car components were modeled, such as:
•
•
•
•
•
•
•
•
•
•
•
Wheels with tire model
Engine and transmission
Steering system
Chassis system with subframe
Fuel tank
Bumper system including crashbox
Radiator with fan
Battery
Spare tire
Brake booster, ABS box and cylinder
Doors, front and rear without glass
The door concept used for all simulations was a typical two shell structure with an
inner and outer panel, an upper door reinforcement and two high strength side
impact beams at the front door and one side impact beam at the rear door.
A three point fixture with reinforcements at the hinges and the locks supported the
doors.
To reduce the model size for the roof crush analysis, the full model with reduced
contents was used (Fig. 6.3.5-1).
Chapter 6 - Page 9
Engineering Services, Inc.
Figure 6.3-1 Crash Analysis Model
A high level of detail of the surfaces, welding and mounting locations was necessary
to provide the resolution to be able to access the events. The LS-DYNA complete
full model had 178386 elements and 174532 nodes.
Chapter 6 - Page 10
Engineering Services, Inc.
The vehicle mass was defined to be base curb weight plus two 50th percentile male
dummies with 113 kg of luggage. The crash mass of the vehicle was set at
1612 kg. The crash mass of the vehicle is calculated as follows:
Curb Mass
1350 kg
Luggage
113 kg
Dummies
149 kg
Total Crash Mass
1612 kg
6.3.1. AMS Offset Crash
The AMS offset crash was defined in the year 1990 by the editor of the German
automotive magazine ‘Auto Motor Sport’ (AMS). The aim of this offset crash is to
secure the passenger compartment residual space. For this requirement a stiff
passenger compartment and a good energy absorption in the front structure is
needed. The initial velocity for the car is 55 km/h for the AMS crash.
The Offset barrier is a block with a 15 degree rotated contact area including two
anti-slide devices mounted on the contact surface. The left side of the car hits the
barrier with an overlap of 50%.
For actual crash tests AMS analyzes the following values:
•
•
•
•
•
•
•
HIC-value (Head Injury Criterion)
Head, chest and pelvis acceleration
Maximum belt forces
Maximum femur forces
Dynamic steering deformation
Foot well intrusions
Door opening after test
Because the analysis did not include dummies, injury assessment could not be
made. Injury performance is greatly affected by the structural crash and steering
column movement as well as by the knee bar design. Evaluation of passenger
compartment intrusion can be made by looking at deformation in the foot well area
(Fig. 6.3.1-4). Looking at the overall shape of the deformation (Fig. 6.3.1-2, -3 can
assess structural integrity).
Chapter 6 - Page 11
Engineering Services, Inc.
Figure 6.3.1-1 AMS Offset Crash Analysis Setup
The AMS Offset undeformed and deformed shapes are shown in Fig. 6.3.1-2 and
6.3.1-3. The deformed shape in these figures is after 100 ms. The deformation in
the footwell area is shown in Fig. 6.3.1-4. The analyzed deformation is measured in
the foot well area where it is important to keep the deformations as low as possible,
because of the injury of the passenger’s legs.
The internal energy absorption diagram in Fig. 6.3.1-5 gives an overview of the
internal energy absorbed in the parts subframe, bumper beam, crashbox, front rail
and fender side rail after 100 ms. The diagram in Fig. 6.3.1-6 shows the load path
for the most important front structure components. The diagram shows the main
load path is the rail front. The fender side rail and the subframe have about the
same load level. The diagram, AMS Offset Crash Acceleration vs. Time (Fig.
6.3.1-7) shows an average acceleration calculated from the rocker LHS, tunnel, and
rocker RHS. After the contact between AMS barrier and engine, a middle
acceleration of about 25 g results in the passenger area. The Figure 6.3.1-8 shows
the function of the car deformation versus time. After about 90 ms the maximum
dynamic deformation is reached.
Chapter 6 - Page 12
Engineering Services, Inc.
t = 0 ms
t = 100 ms
Figure 6.3.1-2 AMS Offset Crash Deformed Shapes
t = 0 ms
t = 100 ms
Figure 6.3.1-3 AMS Offset Crash Deformed Shapes of Longitudinals
Chapter 6 - Page 13
Engineering Services, Inc.
9
40
80
36
39
146
64
134
92
16
33
102
76
60
82
Figure 6.3.1-4 AMS Offset Crash Maximum Dynamic Foot Room Intrusion in mm
Subframe
26.9
Bumper Beam
17.3
Crash Box
5.6
Rail Front
37.6
Fender S. Rail
9.6
0
10
20
30
40
Energy (kJ)
Figure 6.3.1-5 AMS Offset Crash Internal Energy Absorption
Chapter 6 - Page 14
Engineering Services, Inc.
55
Subframe
Front Rail Ext.
50
Rocker
85
115
Rail Front
50
Fender S. Rail
0
20
40
60
80
100
120
140
Force (kN)
Figure 6.3.1-6 AMS Offset Crash Typical Cross Section Forces
Average Car Acceleration vs. Time
Rocker LHS / Tunnel / Rocker RHS
40
-40
30
-30
ax [g]
20
-20
10
-10
0
0
-10
+10
0
20
40
60
80
time [ms]
Figure 6.3.1-7 AMS Offset Crash Acceleration vs. Time
Chapter 6 - Page 15
100
Engineering Services, Inc.
Car Deformation vs. Time
800
600
sx [mm]
400
200
0
-200
0
20
40
60
time [ms]
Figure 6.3.1-8 AMS Offset Crash Deformation vs. Time
Chapter 6 - Page 16
80
100
Engineering Services, Inc.
In the following table (Fig. 6.3.1-9), the AMS crash events vs. time are explained:
Time (ms) AMS Offset Crash
12.00
Initial folding of longitudinal LHS
16.00
Initial folding of subframe
18.00
First buckling of rail upper in front of shock tower
36.00
Wheel LHS contacts barrier
40.00
Engine contacts barrier, start of vehicle-rotation around
z-axis
44.00
Deformable front end of the subframe totally deformed,
stiffer rear end and the extension longitudinal LHS starts
moving rearwards and causes deformation in the front
floor area, buckling of the longitudinal in the area of the
shock tower
48.00
Second buckling of rail upper LHS behind the shock tower
52.00
Buckling of the rear end of the subframe at the fixture on
the extension longitudinals
60.00
Buckling of the brace cowl to shock tower LHS. Engine
hits the steering gear.
68.00
Contact between gearbox-mounting and brake booster
70.00
Wheel LHS hits the hinge pillar
88.00
Maximum dynamic deformation reached
Figure 6.3.1-9 AMS Offset Crash Events
Chapter 6 - Page 17
Engineering Services, Inc.
This analysis shows good progressive crush on the barrier side (left), as well as
crush on the right, indicating transfer of load to the right side of the structure. This
transfer means that the barrier side is not relied upon solely to manage the crash
event.
This transfer also contributes to the preservation of the occupant compartment.
The intrusion of 146 mm into the footwell is minimal given the severity of this event.
The initial, early peak shown in the pulse graph should trigger air bag systems.
Peak deceleration of approximately 35 gs, a good result considering the severity of
this event.
Chapter 6 - Page 18
Engineering Services, Inc.
6.3.2. NCAP 100% Frontal Crash
The conditions for the front crash analysis are based on several requirements. In
the ULSAB program, the focus was on progressive crush of the upper and lower
load path, sequential stack up of the bumper, radiator, and powertrain, integrity
between individual components, A-pillar displacement, definition of the door
opening, uniform distribution of the load, toe pan intrusion, and passenger
compartment residual space. These requirements contribute towards occupant
safety and the United State Federal Motor Vehicle Safety Standard, FMVSS 208.
The test sequence of the front crash analysis is set up to duplicate a 35 mph,
National Highway and Traffic Safety Association (NHTSA) full frontal barrier test
(Fig. 6.3.2-1).
Figure 6.3.2-1 NCAP 100% Crash Analysis Setup
Chapter 6 - Page 19
Engineering Services, Inc.
The NCAP 100% Frontal Crash undeformed and deformed shape is shown in
Figures 6.3.2-2 and 6.3.2-3. The deformed shape in the figure is after 100 ms. The
deformation in the footwell area is shown in Fig. 6.3.2-4. The analyzed
deformations are measured in the foot well area where it is important to keep the
deformations as low as possible, because of the injury of the passenger legs.
The internal energy absorption diagram in Fig. 6.3.2-5 gives an overview of the
internal energy absorbed in the parts subframe, bumper beam, crashbox, front rail
and fender side rail after 100 ms. The diagram in Fig. 6.3.2-6 shows the section
force for the most important front structure components. The diagram shows that
the main load path is the rail front. The components, fender side rail and the
subframe have about the same load level. The diagram, NCAP Crash Acceleration
vs. Time (Fig. 6.3.2-7), is an average of accelerations at the rocker LHS, tunnel,
and rocker RHS. After the contact between barrier and engine it results a middle
acceleration of about 29 g at the passenger area. The Figure 6.3.2-8 shows the
function of the car deformation versus time. After about 68 ms the maximum
dynamic deformation is reached.
t = 0 ms
Figure 6.3.2-2 NCAP 100% Crash Deformed Shapes
Chapter 6 - Page 20
t = 100 ms
Engineering Services, Inc.
t = 0 ms
t = 100 ms
Figure 6.3.2-3 NCAP 100% Crash Deformed Shapes of Longitudinals
80
80
85
70
79
94
70
58
73
62
45
51
50
52
40
Figure 6.3.2-4 NCAP 100% Crash Maximum Dynamic Foot Room Intrusion in mm
Chapter 6 - Page 21
Engineering Services, Inc.
Subframe
30
Rail Upper
12.5
55.3
Rail Front
8
Crash Box
Bumper Front
16
0
10
20
30
40
50
60
Energy (kJ)
Figure 6.3.2-5 NCAP 100% Crash Internal Energy Absorption
Subframe
49
Rocker
50
Rail Upper
41
Rail Front
120
45
Front Rail Ext.
0
20
40
60
80
100
120
140
Force (kN)
Figure 6.3.2-6 NCAP 100% Crash Typical Cross Section Forces
Chapter 6 - Page 22
Engineering Services, Inc.
Average Car Acceleration vs. Time
Rocker LHS / Tunnel / Rocker RHS
40
-40
30
-30
ax [g]
20
-20
10
-10
00
+10
-10
0
20
40
60
80
100
80
100
time [ms]
Figure 6.3.2-7 NCAP 100% Crash Acceleration vs. Time
Car Deformation vs. Time
800
sx [mm]
600
400
200
0
0
20
40
60
time [ms]
Figure 6.3.2-8 NCAP 100% Crash Deformation vs. Time
Chapter 6 - Page 23
Engineering Services, Inc.
The following table (Figure 6.3.2-9) shows the NCAP crash events:
Time (ms) NCAP Front Crash
12.00
Initial folding of longitudinal
16.00
Initial folding of subframe
21.00
First buckling of rails upper in front of shock tower
35.00
Engine contacts barrier
37.00
Buckling of the rear end of the subframe at the fixture on
the extension longitudinals
50.00
Rear end of longitudinals start to buckle behind the
reinforcement (still stable)
51.00
Wheels contacts barrier
67.00
Maximum dynamic deformation reached
Figure 6.3.2-9 NCAP Front Crash Events
This analysis illustrates good progressive crush of the upper and lower structure
and subframe. It shows peak deceleration of 31 gs, which is satisfactory
considering that this structure is designed with stiffer body sides to meet 50% AMS
offset crash requirements.
The pulse graph is sympathetic to current occupant restraint systems. It shows a
consistent rise to the peak of 31 gs then a smooth ride down to zero, indicating that
the occupant would experience controlled restraint. The initial, early peak should
trigger air bag systems. Low intrusion at the footwell indicates that leg damage is
unlikely.
Chapter 6 - Page 24
Engineering Services, Inc.
6.3.3. Rear Crash
The conditions for the rear impact analysis are based on the United States Rear
Moving Barrier Test FMVSS-301. The test specifically addresses fuel system
integrity during a rear impact. Automotive companies also include structural
integrity and passenger compartment volume as additional goals for this test.
The impacting barrier is designed to represent a worst case rear crash (Fig. 6.3.31). The rear crash barrier is a rigid body with a mass of 1830 kg, making contact at
zero degrees relative to the stationary vehicle. The Federal Standard identifies that
the velocity of the rear moving barrier is 30 mph. The ULSAB program has raised
the standard to 35 mph, which is 36% more kinetic energy of the moving barrier.
Evaluating fuel system integrity is done by representing a fuel tank system. The
additional goals of passenger compartment integrity, residual volume, and door
opening after the test can be addressed by looking at the deformed shapes of the
vehicle during the crash event. During the early stages of the impact, there should
be a little or no deformation in the interior. This sequence of events (Fig. 6.3.3-8)
is necessary up to the time that the tires make contact with the barrier face and
transfer load to the suspension and the rear of the rocker panel.
For the rear crash a half structure model was used. The rear crash deformed
shapes are shown in Fig 6.3.3-2. To analyze the rear passenger compartment
integrity, Figure 6.3.3-3 shows that maximum dynamic intrusion in this area.
The diagram (Fig. 6.3.3-4) shows the energy absorption, and the cross sections of
the main hood load paths are shown in Figure 6.3.3-5. Due to the results, the rear
rail and the rocker were the most important hood paths of the rear structure.
The Rear Crash Acceleration vs. Time (Fig. 6.3.3-6) shows an average acceleration
of the rocker RHS and the tunnel. Figure 6.3.3-7 shows the total car deformation, at
approximately 85 ms, the maximum dynamic deformation was reached.
Chapter 6 - Page 25
Engineering Services, Inc.
Figure 6.3.3-1 Rear Crash Analysis Setup
Chapter 6 - Page 26
Engineering Services, Inc.
t = 0 ms
t = 100 ms
t = 0 ms
t = 100 ms
Figure 6.3.3-2 Rear Crash Deformed Shapes
Chapter 6 - Page 27
Engineering Services, Inc.
X
120
X
X
X
53
X
X
73
38
5
X
X
4
X
33
2
Figure 6.3.3-3 Rear Crash Maximum Dynamic Room Intrusion (mm)
Rear Rail
20.2
1.4
Crash Box Rear
Panel Rear Floor
6.3
1.1
Bumper Rear
0
5
10
15
20
25
Energy (kJ)
Figure 6.3.3-4 Rear Crash Internal Energy Absorption (kJ)
Chapter 6 - Page 28
66
Engineering Services, Inc.
Rocker
50
Rear Rail
80
Rail Side Roof
15
20
Spare Wheel
0
10
20
30
40
50
60
70
80
90
Force (kN)
Figure 6.3.3-5 Rear Crash Typical Cross Section Forces (kN)
Average Car Acceleration vs. Time
40
30
ax [g]
20
10
0
-10
0
20
40
60
80
time [ms]
Figure 6.3.3-6 Rear Crash Acceleration vs. Time
Chapter 6 - Page 29
100
Engineering Services, Inc.
Car Deformation vs. Time
800
sx [mm]
600
400
200
0
0
20
40
60
time [ms]
Figure 6.3.3-7 Rear Crash Deformation vs. Time
Chapter 6 - Page 30
80
100
Engineering Services, Inc.
The following table (Fig. 6.3.3-8) explains the rear crash events after impact:
Time (ms) Rear Crash
4.00
Initial folding of longitudinals rear
20.00
Spare tire contacts barrier
35.00
First buckling of crossmember rear suspension
40.00
Spare tire hits crossmember rear suspension
44.00
Buckling of the crossmember rear suspension
48.00
Buckling of the rear end rocker at the connection to
longitudinal rear
52.00
Collapse of crossmember rear suspension
56.00
Buckling of the front end longitudinal rear
86.00
Maximum dynamic deformation reached
Figure 6.3.3-8 Rear Crash Events
This analysis shows that the structural integrity of the fuel tank and fuel filler was
maintained during the event, so no fuel leakage is expected. The spare tire tub
rides up during impact, avoiding contact with the tank.
Rear passenger compartment intrusion was restricted to the rear most portion of the
passenger compartment, largely in the area behind rear seat. This result is due to
good progressive crush exhibited by the rear rail.
Chapter 6 - Page 31
Engineering Services, Inc.
6.3.4. Side Impact Analysis
The conditions for the side impact analysis are based on a European Side Moving
Barrier Test. The European test specifically addresses injury criterion based on
displacement data gathered from EUROSID side impact crash dummies.
Automotive companies also include post-crash structural integrity and passenger
compartment as additional requirements for this test.
The actual European side moving barrier uses a segmented deformable face which
complies with a required set of different load versus displacement characteristics
and geometric shape and size requirements. The barrier used in the analysis (Fig.
6.3.4-1) conformed to the geometric requirements (i.e., ground clearance, height,
width, bumper depth). The European specification requires the impacting barrier to
have a mass of 950 kg, making contact at ninety degrees relative to the vehicle
longitudinal axis. The center line of the barrier is aligned longitudinally with the front
passenger ‘R-point’. The R-point is a car specific point which is defined by the seat/
passenger location. The velocity of the side moving barrier at time of impact is
designated to be 50 km/h.
Because the scope of analysis did not include side impact dummies, injury
assessment could not be made. Injury performance is greatly affected by interior
trim panel and foam absorber design as well as by structural crush. Evaluation of
passenger compartment intrusion can be made by looking at door and B-pillar
displacements and intrusion velocities. Structural integrity can be assessed by
looking at the overall shape of the deformation, including any gross buckling of the
B-pillar, rotation of the rocker rails, crush of the front body hinge pillar, folding of the
door beams and door belts, and cross-car underbody parts such as the seat
attachment members and the rear suspension cross member.
Chapter 6 - Page 32
Engineering Services, Inc.
Figure 6.3.4-1 Side Impact Crash Analysis Setup
The side impact undeformed and deformed shapes are shown in Fig. 6.3.4-2 and
6.3.4-3, with the deformed shapes shown after 80 ms of impact.
During the early stage of the impact, the outer door structure crushes, the B-pillar is
stable. As the impact progresses the rocker starts to buckle and causes also a
bulging of the floor section. At about 30 ms, the still stable structure of the B-pillar
is moved by the barrier inside the car and therefore the roof starts to bulge. After
40 ms the B-pillar develops an inward buckling. After about 64 ms the maximum
dynamic deformation is reached.
For the injury performance, the intrusion velocities of the structural parts, which
could come in contact with the passengers, are important. Figures 6.3.4-5 and
6.3.4-6 show the intrusion velocities of typical points at the inner front door panel
(No. 238) and the B-pillar inner (No. 235) (Fig.6.3.4-4).
The following Figures 6.3.4-2 and 6.3.4-3 show the deformed shape of the side
structure:
Chapter 6 - Page 33
Engineering Services, Inc.
t = 0 ms
t = 80 ms
Figure 6.3.4-2 Side Impact Crash Deformed Shapes
Chapter 6 - Page 34
Engineering Services, Inc.
t = 0 ms
t = 80 ms
Figure 6.3.4-3 Side Impact Crash Deformed Shapes of Side Structure
No. 238
No. 238
No. 353
No. 353
Measured points for velocity
Lower B-pillar enlarged
Figure 6.3.4-4 Side Impact Time History Node
Chapter 6 - Page 35
Engineering Services, Inc.
Velocity vs. Intrusion
Door Inner Panel
No 353
10
9
8
Y - Velocity [m/s]
7
6
5
4
3
2
1
0
-1
-2
0
50
100
150
200
250
300
250
300
Y - Intrusion [mm]
Figure 6.3.4-5 Side Impact Velocity vs. Intrusion at Node 353
Velocity vs. Intrusion
B-Pillar
No 238
10
9
8
Y - Velocity [m/s]
7
6
5
4
3
2
1
0
-1
-2
0
50
100
150
200
Y - Intrusion [mm]
Figure 6.3.4-6 Side Impact Velocity vs. Intrusion at Node 238
Chapter 6 - Page 36
Engineering Services, Inc.
The following table (Fig. 6.3.4-7) shows the side impact crash events:
Time (ms) Side Impact
16.00
Buckling of the rocker in front of B-pillar
28.00
Buckling of the floor
35.00
Buckling of the roof
40.00
Buckling of the roof frame at the B-pillar
44.00
Buckling of the member kick up, still stable
48.00
Buckling of the brace tunnel
64.00
Maximum dynamic deformation reached
Figure 6.3.4-7 Side Impact Crash Events
The body side ring and doors maintained their integrity with only 248 mm of
intrusion. The velocity of the intruding structure was tracked to determine the
degree of injury an occupant may sustain. The maximum velocity was only
8 meters per second. The event is considered complete when the deformable
barrier and vehicle reach the same velocity, in this case at 64 msec.
Chapter 6 - Page 37
Engineering Services, Inc.
6.3.5. Roof Crush (FMVSS 216)
The conditions for the roof crush analysis are based on United States, FMVSS 216.
This requirement is designed to protect the occupants in event of a rollover
accident. The surface and angle of impact are chosen to represent the entire
vehicle impacting the front corner of the roof.
The federal standard requires roof deformation to be limited to 127 mm (5 inches) of
crush, and roof structure to support 1.5 times the vehicle curb mass or 5,000 lbs
(22249 N), whichever is less.
For test purposes and repeatability, the complete body in white is assembled and
clamped at the lower edge of rocker and the roof crush test is done in a quasi-static
force versus displacement arrangement. In the computer analysis, the software
program, LS-DYNA, requires that the roof crush be done in a dynamic, moving
barrier description as compared to the quasi-static test.
Figure 6.3.5-1 shows the undeformed shape of the FE-Model used for the roof crush
simulation. The shape of the structure after the limit of 127 mm deformation is
shown in Figure 6.3.5-2.
The force versus displacement curve is shown in Fig 6.3.5-3. The peak force of
36150 N is reached after a deformation of 72 mm of roof crush. Based on the curb
mass of 1350 kg, the crush force of 19865 N is required for the federal standards
FMVSS 216. The analysis was continued to 127 mm (5 inches) of deflection in
order to determine the ability of the roof to sustain the peak load past 72 mm of
crush. The analysis shows that the roof meets the peak load requirements and is
steady and predictable.
Chapter 6 - Page 38
Engineering Services, Inc.
Figure 6.3.5-1 Roof Crush Undeformed Shape
Figure 6.3.5-2 Roof Crush Deformed Shape
Chapter 6 - Page 39
Engineering Services, Inc.
Force vs. Deformation
40
127
35
30
Force [N]
25
20
15
10
5
0
-5
0
25
50
75
100
125
150
Deformation [mm]
Figure 6.3.5-3 Roof Crush Deformation vs. Force
Analysis showed that 22.25 kN was reached within 30 mm of crush. The structure
resisted the applied load all the way up its peak of 36.15 kN and continued to
maintain it quite well even after peak, when it dropped to about 28 kN at 127 mm.
The load was well distributed through the A, B and C-pillars and down into the rear
rail.
6.4. CAE Analysis Summary
For the AMS Offset crash test the overall deformation and intrusion are the critical
figures. For the NCAP crash test, the critical figure is the vehicle crash pulse. The
target for the offset crash was to achieve low footwell intrusion. It is important to
achieve a good balance between these two targets. The results of the crash
analysis show that for the ULSAB a good compromise has been found to fulfill the
AMS as well as the NCAP frontal crash, considering the dependencies between
these two crash types.
To achieve the low footwell intrusion for the AMS crash a rigid front structure is
needed. A rigid front structure, however, means higher acceleration in the NCAP
Chapter 6 - Page 40
Engineering Services, Inc.
test and results in higher HIC (Head Injury Criteria) values for the passengers, with
a maximum footwell intrusion of 149 mm for the AMS Offset crash and a maximum
acceleration of 30.4 g for the NCAP crash, the ULSAB structure shows a good
balance in these criteria. The results also document the high safety standards of
ULSAB, especially if one considers that the NCAP crash analysis was run at 5 miles
above the required speed of 30 mph and 36% more energy had to be absorbed.
The rear crash test requirements are addressing the fuel system integrity and low
deformation in the rear seat area. The analysis shows no collapse of the
surrounding structure of the fuel tank, contact with the fuel tank itself or the fuel filler
routing. Considering the fact that there was no rear seat structure the analysis also
shows a low deformation of the rear floor. For the rear crash analysis in the ULSAB
program, the requirement was raised from 30 mph to 35 mph velocity of the rear
moving barrier, resulting in an increase of 36% of its kinetic energy.
In the side impact crash test, good performance means acceptable intrusion of the
side structure at low intrusion velocity. For both criteria the ULSAB achieved
satisfactory results. The analysis shows a maximum intrusion of 250 mm and an
intrusion velocity of 8 m/s at the inner door panel and the B-pillar. It is assumed that
in a fully equipped car the intrusion will be even lower.
For the roof crush test the Federal standard requires the roof deformation to be
limited to 127 mm of crush and the structure to support 1.5 times the curb mass or
5000 pounds, whichever is less. The force requirement of 19500 N was already met
at 27 mm of crush. The continued analysis showed that the structure is steady and
peak load of 36 kN was met after 72 mm of crush. This result confirms the role the
side roof rail plays as important part of the ULSAB structure.
The ULSAB crash analysis has shown that reducing the body structure mass using
high strength steel, in various grades and in applications such as tailor welded
blanks combined with the applied joining technologies in the assembly, such as
laser welding, does not sacrifice safety.
The goal was to maintain the high standards of state-of-the-art crash requirements,
without compromising the ULSAB program goal to significantly reduce the body
structure mass. The crash analysis of the ULSAB supports that this goal is
reached.
Chapter 6 - Page 41
Engineering Services, Inc.
7. Material & Processes
Engineering Services, Inc.
7. Material and Processes
7.1. Material Selection
7.1.1. Material Selection Process
Based on ULSAB Phase 1 results, the body structure was redesigned in Phase 2 as
described in earlier chapters of this report. With respect to the new influences,
such as crash requirements and styling, new calculations had to be made. The
calculations concerning static behavior gave us a first indication of the sheet metal
thickness needed. This is because performance is mainly related to sheet metal
thickness and the design itself, and not to the strength of the material, because the
E-modulus is very similar for all steel types. After the initial material selection, the
first loop of crash calculations was performed. As a result, the material grades and/
or the sheet metal thicknesses had to be adjusted.
Several iterations of the “Material Selection Process” (Figure 7.1.1-1) lead us to the
optimal strength/thickness level for each part. This procedure included a
manufacturing feasibility check with our selected part suppliers. For the most
critical parts, a forming simulation was performed simultaneously by the steel
suppliers. The results of these simultaneous engineering processes have been
important factors in successfully meeting the challenges of developing
manufacturable parts. Different criteria during the material selection process such
as formability, weldability, spring-back behavior, and static and dynamic properties
were always taken into consideration.
Always having “Production Intent” in mind, the focus was on production-ready
materials, not on materials that are available only in laboratory scale. General
material specifications and the definition of the different material grades are
described in section 7.2 of this chapter.
Chapter 7 - Page 1
Engineering Services, Inc.
Material Selection Process
No
Start
Phase 1
Package /
Concept Design
Phase 2
Package
Refinement
Create
Styling Concept
Modify Package/
Styling / Design
Modify Phase 1
Shell Model
Steel Supplier
and Part Supplier
Input
Modify Design
Material / Thickness
Adjustement
Meets
Static
Targets
Yes
No
Meets
Static/Crash
Targets
Create / Modify
Phase 2 Crash Model
Yes
Meets
Static
Targets
Create / Modify
Phase 2 Shell Model
Material / Thickness
Selection,
Design Modification
No
Yes
No
No
Yes
Parts Feasible
Build of First
Test Unit
Meets
Static / Crash
Targets
Yes
Build of Final
Demonstration Hardware
Figure 7.1.1-1
7.1.2. Definition of Strength Levels
In order to use the minimum variety of materials, every “master item” was defined
by thickness and strength. The same master item could be used for different parts,
as long as thickness and strength requirements were met, and the part suppliers
and forming experts had no concerns. The definition of strength levels as used in
ULSAB Phase 2 is shown next in the “ULSAB High Strength Steel Definition.”
Chapter 7 - Page 2
Engineering Services, Inc.
ULSAB High Strength Steel Definition
The ULSAB program designates steel grades by specified minimum yield strength
in the part. The following steel grades are utilized in the ULSAB design:
Minimum
Yield Strength
Category
140 MPa
Mild Steel
210 MPa
High Strength Steel
280 MPa
High Strength Steel
350 MPa
High Strength Steel
420 MPa
High Strength Steel
Greater than 550 MPa
Ultra High Strength Steel
This definition was chosen in order to standardize the steel grade definitions for the
ULSAB Consortium member companies since many countries are involved and the
standards are not the same around the world. This has to be seen together with the
goal that the ULSAB body structure could be built in every region of the world where
steel is available. This is also the reason that the suppliers of the material for the
DHs are kept anonymous within the ULSAB program.
The most suitable material for each part application was chosen with the assistance
of experts from the steel suppliers. This process was especially important for the
ultra high strength steel because of its more critical forming behavior. Different
materials such as dual phase (DP) steels are included in this group of ultra high
strength material parts.
There are several ways to achieve the 280 MPa yield strength level according to the
above definition. This could be done by using microalloyed high strength steel,
bake hardening or even dual phase steel. However it is achieved, the minimum
yield strength for the finished part has to be 280 MPa in each area of the part.
Other material qualities and material types could achieve the same or similar
results; therefore, several factors affected material selection including material
performance and availability.
Chapter 7 - Page 3
Engineering Services, Inc.
7.1.3. Supplier Selection
Once the “master items” were defined, the material supplier selection was made.
This was done in material group meetings attended by all steel supplier experts and
the design and manufacturing team of PES. For every part of the ULSAB, a
minimum of two material sources were selected.
The fact that different materials with the same yield strength level were available for
each part (not only from different suppliers, but also in many cases different
material types, such as microalloyed or dual phase) shows that most of the ULSAB
parts could be made in multiple ways. No specially treated or designed material
was necessary. Most of the material was taken from normal serial production at the
steel mills.
In order to practice simultaneous engineering most efficiently, the material suppliers
were selected by their close proximity to the part supplier’s location (press shop). If
the material failed during the first try-outs it was easier to react with corrective steps
such as circle grid analysis, material tests, or forming simulations.
Similar criteria were used in selecting the welding sources for the tailor welded
blanks. In most cases two different companies could have provided the same
welded sheet, each with slightly different material qualities. This again underscores
that the ULSAB can be built with widely available material and part manufacturing
technology.
Chapter 7 - Page 4
Engineering Services, Inc.
7.2. Material Specifications
7.2.1. General Specifications
General specifications for the material used on the ULSAB only concerned
thickness tolerances, coating requirements and coating tolerances. The
specifications are as follows:
•
•
•
Actual thickness of blanks must measure +0.00 mm/-0.02 mm of the
specified thickness
Coating may be electro-galvanized (Zn only) or hot dip (Zn or ZnFe)
Coating thickness must be 65 gram/m² maximum (0.009 mm) per side with
coating on both sides
Every delivered material had to be tested at the supplying source before it was
shipped to the part manufacturer. A test report accompanied the material until the
parts are finished. This is the basis for the Advanced Quality Planning (AQP) report
that was performed by the ULSAB Consortium. The test results are also considered
for welding parameter evaluation at the prototype shop.
7.2.2. Material Classes
7.2.2.1. Mild Steel Definition
Mild steel, which is described in Sec 7.1 Material Selection, is material with a yield
strength level of 140 MPa. Mild steel can also be defined in terms of “Draw Quality,”
“Deep Draw Quality” or “Extra Deep Draw Quality.” The material has no fixed
minimum yield strength but does have a minimum elongation. Mild steels are the
most common steels used in auto making today. This is because mild steel has
forming and cost advantages compared to high strength steel. On the other hand,
the ULSAB clearly shows that the amount of high strength and ultra high strength
steel can be used up to more than 90% or more without any cost penalty.
Chapter 7 - Page 5
Engineering Services, Inc.
7.2.2.2. High Strength Steel Definition
The steel industry has developed various high strength steel qualities. In the
ULSAB Phase 2 program the strength levels of 210, 280, 350 and 420 MPa were
defined as high strength steel. The values are related to the strength of the finished
parts as assumed in the FEA model. This includes additional strengthening as a
result of the bake-hardening process also.
High strength steels were used where the design required certain crash and
strength characteristics. Within the range of this material group, different
strengthening mechanisms can contribute to the final result. The DHs used microalloyed steels, phosphor-alloyed steels, bake-hardening steels, isotropic steels,
high-strength IF - steels and dual-phase steels, all in the range of the abovementioned yield strength. This engineering report does not include a detailed
description of alloying or other metallurgical processes that are used to produce
those steel types.
7.2.2.3. Ultra High Strength Steel Definition
Ultra high strength steels are defined as steels with a yield strength of more than
550 MPa on the finished part. Parts made from these steels can provide additional
strength for front and side impact. In the ULSAB structure, all crossmembers of the
floor structure were designed in ultra high and high strength steel.
Today, there are different ways to achieve needed strength levels. This could be
done for automotive sheet panels with dual phase (DP) steels, or with boron-alloyed
types, which have to be hot formed. Within the ULSAB Phase 2, parts were made
from DP steels. DP steels were feasible even on parts with a complex shape like
the cross member dash. As of today, those types were also available in an
appropriate thickness range, which is interesting for automotive applications, e.g. a
thickness between 0.7 and 1.5 mm.
Chapter 7 - Page 6
Engineering Services, Inc.
7.2.2.4. Sandwich Material Definition
The use of sandwich material has contributed to considerable mass savings on the
ULSAB. The sandwich material is made with a thermoplastic (polypropylene) core,
which has a thickness of about 0.65 mm. This core is “sandwiched” between two
thin outer steel sheets with a thickness of about 0.14 mm each. The polypropylene
core of this sandwich material acts as a spacer between the two outer sheets,
keeping the outer surfaces away from the neutral axis when a bending load is
applied (see fig. 7.2.2.4-1). The mentioned material (total thickness about 0.96 mm
when coated) has a very similar behavior compared to a solid sheet of steel with a
thickness of about 0.7 mm.
Steel Sheet 0.14 mm
Polypropylene Core 0.65 mm
Steel Sheet 0.14 mm
Figure 7.2.2.4-1 Sandwich Material
This sandwich material shares many of the same processing attributes with steel
sheets, like deep drawing, shear cutting, bonding, etc. But, unfortunately, it cannot
be welded. Even mechanical joining like riveting, clinching or screwing, can be a
problem when the material has to go through the paint-baking oven. The core
material is softened by the heat and flows away from the area where a pretension
from a screw is applied. This may lead to a loss in joining strength.
Therefore, applications used in the ULSAB Phase 2 design were with parts made
from sandwich material that did not go through the oven. The spare tire tub is
designed as a prepainted module, preassembled with spare tire and tools. This
module will be dropped into place and bonded to the structure during the final
assembly of the vehicle. No additional heat has to be applied. Another application
of sandwich material is the dash panel insert, which was bolted and bonded into the
panel dash during final vehicle assembly.
Chapter 7 - Page 7
Engineering Services, Inc.
Because there was no application similar to the spare tire tub in the past, an
extensive forming simulation was performed on this part. Once the design was
adjusted using the results of the simulation, there were no major concerns about the
feasibility of the spare tire tub. After a small refinement of the best drawable radius,
the parts were determined to be manufacturable with no problems.
Furthermore, a physical test with the spare tire tub was performed to check the
fatigue behavior of this material for the application. Parts from the described
sandwich material were made and compared to parts made from solid steel sheets
of 0.7 mm thickness. A picture of the test installation is shown below in Fig.
7.2.2.4-2.
F
Figure 7.2.2.4-2 Test Installation
Chapter 7 - Page 8
Engineering Services, Inc.
The load signal that was applied was taken from Porsche’s proving ground and
adjusted to the situation of the ULSAB. The test concluded there are no restrictions
for the use of the sandwich material for the proposed application when it is
compared to a conventional design using a 0.7 mm solid steel sheet.
The parts that were designed for the ULSAB could be made up to 50% lighter than
those made of solid steel under similar dimensional and functional conditions. But,
higher costs for the sandwich material have to be taken into consideration as
compared to normal coated steel sheets.
7.2.3. Material Documentation
As mentioned earlier, every “Master Item” (material defined by thickness and
strength) was accompanied by a test report, which includes all important strength
properties, r- and n- values and a coating description. Those tests were performed
by the supplying steel mills. All the supplied materials are documented at PES with
their corresponding values, such as blank size, properties, coatings, material type
etc. The “Master List” was also the base for the documentation of the welding
parameters and the DH build itself.
When the parts were manufactured, the above-mentioned documentation was
completed with additional information concerning press conditions for parts made at
different locations. For those parts where a forming simulation and/or a circle grid
analysis were performed, the documentation was extended with the results from
these additional steps. These results are included in the earlier mentioned AQP
report.
To ensure proper and comparable documentation, material samples from every part,
that goes into the DH were collected by PES and sent to a central testing source.
At this neutral location, every collected material was tested in the same way and
documented again.
Chapter 7 - Page 9
Engineering Services, Inc.
7.3. Tailor Welded Blanks
Introduction
Tailored blanking for vehicle body structures is a well known process with the first
applications being done for mass production which started in 1985. Below listed are
the main reasons for PES´s decision to use tailor welded blanks in a relatively large
number compared to vehicles already on the market:
•
•
•
•
•
•
•
Mass reduction due to the possibility of placing optimum steel thicknesses
and grades where needed
Elimination of reinforcements with appropriate material gage selection
Simplified logistics due to the reduction of parts
Investment cost reduction of dies, presses etc. due to fewer production
steps
Better corrosion protection by the elimination of overlapped joints
Improved structural rigidity due to the smoother energy flow within the
tailor welded blank parts
Better fatigue and crash behavior compared to a conventional overlapped
spot welded design solution
7.3.1. Selection of Welding Process
Laser welding and mash seam welding are the most common processes for the
manufacturing of tailor welded blanks today. Induction and electron beam welding
have a minor importance and they are still under development. All these processes
have their advantages and disadvantages, related to the process and the machine
itself.
Induction welding is a butt welding process. The necessary compressing of the two
sheets creates a bulge with the consequence of an increase in thickness in the
joined area. Those blanks could not be used in visible areas without an additional
surface finishing process. A high accuracy during the movement of the sheets is
important. The heating of the weld seam by induction / magnetic current over the
total length leads to a larger heat affected zone when compared to laser welded
blanks.
Chapter 7 - Page 10
Engineering Services, Inc.
The non-vacuum electron beam welding process is similar to laser welding in the
result of the weld seam geometry. This is due to the fact that it is a non-contact
process as well. The beam is a mass beam and the kinetic energy of this beam is
used for heating the material. The beam can be focused by a magnetic spool and
the diameter can be adjusted easily. The advantage of this process compared to
laser is the increased efficiency of about 90% compared to 10% when using laser.
But a disadvantage is that the electron beam creates x - rays. This influences the
machine design dramatically regarding total investment and material handling.
Therefore this process is not used extensively up to now.
Mash seam welding needs a narrow overlapping of the sheets which have to be
welded. The material in this area becomes doughy, not really fluid. During the
welding process the current flows from one electrode to the other one and by
resistance heating the sheet material becomes doughy. The electrode force then
mashes the weld area and the sheets are joined together in this way. This light
overlap and the joining process by force loaded electrodes results in a weld zone
between 2.5 and 3.0 mm. The coating maybe is affected in this zone negatively.
Furthermore, experience has shown that the surface of the weld zone, where little
caves and pinchers occur due to the mash welding process, may not achieve the
required corrosion resistance.
The laser welding process is used more and more widely. It is a non-contact
welding process, and the heat is brought into the material by a coherent light with
high energy density. In this way a very narrow weld zone can be achieved. There is
almost no influence on the corrosion resistance when coated material is used. The
main critical point on this process is without any doubt the need for very precisely
prepared edges of the sheet. But this problem could be overcome by today’s
available precise cutting technologies or advanced fixing and clamping devices.
One of the biggest advantages is the possibility of a non-linear weld line layout.
Different combinations of laser sources and clamping devices are on the market
today. In many cases the sheets are moved relative to the fixed laser beam. This
may lead to a reduction of the cycle time of the whole process.
Chapter 7 - Page 11
Engineering Services, Inc.
Together with the fact that most of the newest installations for welding blanks are
laser equipped devices, and the positive experience of PES, has lead to the
decision to use laser welded tailored blanks on the ULSAB body structure
exclusively. The blanks were produced at different locations using different
equipment from the whole range of possible installations. The weld lines were
controlled during the joining process to maintain the following features:
•
•
•
•
•
width of the remaining gap
mismatching of blank edges
blank position
seam geography (concavity, convexity)
lack of penetration
All of these lead to the high quality of today’s tailor welded blanks.
7.3.2. Weld Line Layout
The weld line layout was mainly driven by the crash calculation results. Forming
feasibility requirements also influenced it. On some of the most critical parts, e.g.
the body side outer panel, a forming simulation was performed. Necessary changes
from this simultaneous engineering process were incorporated in the weld line
layout.
The following parts on the ULSAB body structure were designed as tailor welded
blanks:
•
•
•
•
•
•
•
•
Front Rail Outer
Front Rail Inner
Panel Rocker Inner
Rear Rail Inner
Rear Rail Outer
Panel Body Side Outer
Panel Wheelhouse Outer
Panel Skirt
Chapter 7 - Page 12
Engineering Services, Inc.
The weld line layout is shown in the following pages for each part.
ULSAB 008 - Rail Front Outer
1.6
1.5 (350 MPa) (350 MPa) 2.0 (350 MPa)
ULSAB 010 - Rail Front Inner
1.5 (350 MPa)
1.6
(350 MPa)
1.8 (350 MPa)
ULSAB 042 - Panel Rocker Inner
1.7 (350 MPa)
1.3 (350 MPa)
Chapter 7 - Page 13
Engineering Services, Inc.
ULSAB 046 - Rail Rear Inner
1.6 (350 MPa)
1.3 (350 MPa)
1.0 (350 MPa)
ULSAB 048 - Rail Rear Outer
1.6 (350 MPa) 1.3 (350 MPa)
1.0 (350 MPa)
ULSAB 060 - Panel Body Side Outer
1.3 (280 MPa)
0.7 (210 MPa)
1.5
(350 MPa)
1.7 (350 MPa)
Chapter 7 - Page 14
0.9 (280 MPa)
Engineering Services, Inc.
ULSAB 070 - Panel Wheelhouse Outer
0.8 (210 MPa)
0.65 (140 MPa)
ULSAB 096 - Panel Skirt
2.0 (140 MPa)
1.6 (140 MPa)
Chapter 7 - Page 15
Engineering Services, Inc.
7.3.3. Production Blank Layout
Figure 7.3.3.-1 For the Economic Analysis cost calculation purposes, the production blank
layout for the tailor welded blank parts was developed.
7.4. Hydroforming
7.4.1. General Process Description
Today, tubular hydroforming is a well-established process in automotive
manufacturing. When ULSAB Phase 1 began several years ago and hydroforming
was chosen as the manufacturing process for the side roof rail, the technology was
being used mainly for exhaust pipes and some front cradles. These had a much
smaller diameter-to-thickness ratio compared to the ULSAB side roof rail. But with
the focus on mass savings, it was assumed that hydroforming could reduce the
number of parts while helping to optimize available package space.
Chapter 7 - Page 16
Engineering Services, Inc.
The hyroforming process is described very simply as: “put a tube between a lower
and an upper die, close the die, fill the tube with water and increase the internal
pressure in order to force the tube to expand into the shape of the die.” However,
several things must be taken into consideration within this process technology. This
method will work only for straight tubes. In all other cases the tube has to be prebent or preformed depending on the final shape. The various steps necessary for
the manufacturing of the ULSAB side roof rail will be explained in the next section.
7.4.2. Benefit for the Project
As explained in the Phase 1 report, the use of hydroformed parts instead of
conventionally formed and spot-welded structures have certain apparent
advantages. Because of the absence of flanges, available space could be utilized
with higher efficiency (bigger cross sections were achievable). The homogeneous
hydroformed parts also provide an improved load flow in comparison to other
structural members made of several parts joined by spot welding. The side roof rail
represents a significant structural member in the ULSAB structure and provides an
optimal load distribution from the A-pillar along the roof into the B and C-pillar. This
is true for the static as well as for the dynamic behavior of the body structure. Also
the side impact and the rear crash support is affected positively. The interior of the
vehicle is well protected by the “roll bar” design of these two structural members
integrated into the body structure.
The hydroformed parts described in ULSAB Phase 1 already have led to similar
applications in vehicles that are on the road today. There is a high potential for
further steel applications on comparable parts that are loaded with high forces.
Other opportunities for hydroformed steel structures will be in the area of protection
systems for convertibles.
Chapter 7 - Page 17
Engineering Services, Inc.
7.4.3. Forming Simulation (Review)
First, a feasibility check was made using the predicted bending line along with
analyzing the material distribution over the circumference in different cross sections.
Next, the design of the side roof rail was analyzed and optimized for feasibility by
conducting a forming simulation. Simultaneous engineering was used by the team
consisting of PES and the part manufacturer; a similar approach was used for the
development of the conventional stamped parts.
Conducting a forming simulation for parts like the side roof rail is much more
complex than for stamped parts. This is because material properties that are
affected by a combination of processes such as prebending, preforming and
hydroforming are very difficult to calculate. The first forming simulation has shown
that wrinkles will occur during a very early stage of the forming process in the area
where the tube was first prebent. The next step is to preform in a different direction
to make it fit into the hydroforming tool. A picture of this area taken from the
forming simulation program is shown in Figure 7.4.3-1.
Figure 7.4.3-1 Forming Simulation
As a result of this analysis the design of the side roof rail was modified so that
some bending radii were softened. Also some other areas were slightly changed in
order to prevent excessive material thinning or cracking during the forming process.
The forming simulation also led to the decision of using a separate preforming tool
(described in Sec. 7.4.5).
Chapter 7 - Page 18
Engineering Services, Inc.
7.4.4. Tube Manufacturing
Certain material qualities have to be defined. Standard tubes, beside the fact that
the required diameters with the needed thin wall were not available commercially,
have no high demand concerning transversal elongation. But this is one of the main
factors during the hydroforming process when the tubes are expanded. Even if the
difference in diameter on different cross sections of the tube is relatively low, certain
areas of the ULSAB hydroformed side roof rail required a high degree of elongation.
During the design process, differentiation must be made between local elongation
(between two points of the circumference) and the overall elongation (total
difference in circumference in a cross section). These two factors must also be
taken into consideration for the longitudinal shape of the part. Transitions between
shape changes of the cross sections should be as smooth as possible and high
elongation is needed.
The above mentioned facts led to the decision to manufacture tubes for the ULSAB
side roof rail from material different to what is used for conventional tubes. Tubes
were made, therefore, from high strength steel sheets to meet yield strength
requirements and to have uniform elongation in both directions. High work
hardening, which should be achievable by this material, is an important factor as
well.
Tubes can be made in several different ways. One way is to manufacture them with
a continuous roll forming and high frequency welding. This has to be done with
extremely high accuracy of the weld geometry especially on such thin walled large
diameter tubes. Because the burr (which is unavoidable in this process) has to be
removed in an additional planing operation (scarfing), not all of the welds are able to
meet the tube specifications. Another approach is to use non-contact laser welding
for the joining process. This eliminates the burr and therefore no additional
operations are needed; it also creates a much-narrowed heat-affected and dezinced zone. For these reasons the tubes for the ULSAB structure were laser
welded.
Chapter 7 - Page 19
Engineering Services, Inc.
For the prebending process, which requires a tube with small tolerances and a
finished part with high strength, the following tube specifications were created:
Quality
Feature:
Material:
Yield Strength:
Total Elongation:
Uniform Elongation:
r - Value:
Precision steel tube according to the following tolerances
Zinc coated on both sides details see below
> 260 N/mm² (> 280 N/mm² on finished parts)
> 32% (longitudinal and transverse)
> 20%
> 1.80
Dimensions and Tolerances
Outside Diameter:
96 mm +0.1 / 0
Wall Thickness:
1.0 mm; tolerances according to ULSAB specification
Total Tube Length:
2700 mm +/- 1
Cutting of Tube Ends: Free of Burr
No ovalization or cave-in
No chamfers
Rectangular to longitudinal axis +/- 0.5°
Appearance of Tubes
Surface:
Free of mechanical damage, splatters, etc.
No collapsed areas (no indents, bulges, etc.)
Free of impurities (swarf, weld chips etc.)
Welding Requirements
Welding Process:
Laser- or high-frequency welding
Weld Seam Area:
Outside of tube: Undercut 0.0 mm, no expansion
Inside of Tube: Undercut < 0.2 mm, no expansion
No mismatch of edges
Free of any porosity
Strength similar to base material
Chapter 7 - Page 20
Engineering Services, Inc.
7.4.5. Process Steps for Rail Side Roof
Because the side roof rail has several 2-dimensional bendings with different radii
over its length and two 3-dimensional curves in the rear portion, the straight tube
has to be prebent. At the beginning of the design phase, bending tubes with such a
high diameter (96 mm) -to-wall-thickness (1.0 mm) ratio resulted in very poor bend
quality. At first, the tubes were bent by using a conventional mandrel-bending
machine modified in such a way that the mandrel was replaced by internal fluid
pressure. This inside pressure is working as a substitute for a mandrel. The
purpose of this was to maintain stricter tolerances which are directly related to the
accuracy of the bending tools, the diameter of the mandrel used, and the tube
diameter and wall thickness. In this way, the tubes could be bent into the needed
shape without any wrinkles. However, because the pressure was applied inside the
whole tube, the tube diameter increased to a point that the tube would not fit into
the next die. Therefore, Porsche went back to using the solid mandrel. By holding
to stricter tolerances and taking certain other steps, wrinkle-free tubes could be
formed. With this process, the clamping force needed to avoid wrinkles or damage
to the tube has to be kept within a tight tolerance.
Once the tube is prebent, preforming is the next step. This is done in a three-piece
tool under low internal pressure to avoid collapsing. The tube is then flattened and
bent again in order to fit into the final hydroforming die. The basic layout of the
preforming tool and the tool itself is shown in Figure 7.4.5-1, 2 & 3.
Outer tool part
Tube
Section A - A
Moving direction of
outer tool part
Inner tool part
Upper tool part
not shown
Figure 7.4.5-1 Preforming Tool Concept
Chapter 7 - Page 21
Engineering Services, Inc.
Tube filled with water
under low pressure
Outer tool part moved
to inner pert
Upper tool part closed
Pressure released and
die opened
Figure 7.4.5-2 Sec. A-A of Preforming Tool Concept
Upper tool part
Inner tool part
Outer tool part
Figure 7.4.5-3 Preforming Tool
Chapter 7 - Page 22
Engineering Services, Inc.
The final step is the hydroforming process itself. During the down movement of the
upper half of the die there is another area preformed again (under low internal
pressure) on the tube. This must be done because the hydroforming process is
very sensitive to die locking. Once the die is finally closed, the internal pressure is
increased and the side roof rail tube is calibrated into its final shape. The pressure
has to be raised to 900 bar for the side roof rail in order to set the final shape of the
part. This required a closing force of about 3200 tons. This internal calibration
pressure was higher than predicted by calculation and forming simulation. A picture
of the hydroforming tool is shown in Fig. 7.4.5-4.
Figure 7.4.5-4 Hydroforming Tool
Chapter 7 - Page 23
Engineering Services, Inc.
7.4.6. Results
Hydroforming has never been used previously to form a high strength steel tube
with such a high diameter-to-wall-thickness ratio. Nevertheless the goal to
manufacture the side roof rails was achieved. There is still room for improvement,
but the main problems related to the bending and preforming operations were
resolved. Hydroforming will be only a calibration operation if all-important steps
before this were optimized. With the experience gained from the ULSAB Phase 2,
producing similar hydroformed applications should be easier in the future.
Chapter 7 - Page 24
Engineering Services, Inc.
7.5. Hydromechanical Sheet Forming
7.5.1. General Process Description
Hoods, roofs and door panels (large body outer panels) produced by conventional
forming methods often lack sufficient stiffness against buckling in the center area of
the part. Due to the low degree of deformation in the center, there is only a little work
hardening effect that could be achieved. Therefore, material thickness has to be
increased to meet the dent resistance requirements on those parts. This of course
leads to heavier parts and creates extra costs. The “active hydromechanical sheet
metal forming process” is a forming technology that uses an active fluid medium.
The die consists of three main components: a drawing ring, which is designed as a
“water box,” the blankholder (binder) and the drawing punch itself. At the beginning,
the die is open and the blank is loaded on the ring (see figure 7.5.1-1).
Slide Cylinder
Blankholder Cylinder
Slide
Blankholder
Moving Balster
Figure 7.5.1-1 Active Hydro-Mec Process Step: Loading / Unloading
Chapter 7 - Page 25
Engineering Services, Inc.
In the second stage, the die is closed and the blankholder clamps the blank. The
die punch has a defined, part specific regress against the clamped blank, as in
figure 7.5.1-2. A pressure intensifier is used to introduce the water emulsion into
the water box, where a pre-set pressure is generated. The blank is inflated in a
controlled manner and stretched over the complete area until it is pressed against
the punch. This is the reason why the process is called “active hydromechanical
sheet metal forming.” Forming with fluids (or flexible rubber layers) is well known
already, but previously there was no forming in the “opposite” direction within those
processes. The plastic elongation produces a work-hardening effect, especially in
the center of the part. This effect significantly improves the dent resistance of the
formed part.
Figure 7.5.1-2 Active Hydro-Mec Process Step: Pre-forming
Chapter 7 - Page 26
Engineering Services, Inc.
Once the first plastic elongation process is done, the draw punch is moved
downward, as in figure 7.5.1-3. At the same time, the emulsion is evacuated from
the water box and the pressure of the fluid is lowered in a controlled process. After
completion of the drawing operation, pressure is increased once more in order to
calibrate the part into the final shape. The later visible surface of the part (outer
side) is turned towards the active fluid medium. There is no contact to metal on this
surface and an excellent surface quality of the part was achieved.
Source: SMG Engineering Germany
Figure 7.5.1-3 Active Hydro-Mec Process Step: Forming Completed
Chapter 7 - Page 27
Engineering Services, Inc.
A picture of the formed roof panel is shown below in figure 7.5.1-4.
Figure 7.5.1-4 Roof Panel
7.5.2. Benefit for the Project
The active hydromechanical sheet metal forming process is characterized by
improved component quality and potential mass and cost reduction. The essential
features of this new technology are: higher dent resistance achieved by an
increased work-hardening effect during the first “counter” forming operation, and
superior visible surface quality achieved by using water instead of a metal die for
the final forming operation. This leads to a reduced component mass due to
increased stability. Sheet thickness could be reduced to 0.7 mm and reinforcement
elements could be saved, while all other requirements were still fulfilled. In
addition, the cost of dies can be reduced by about 40% because only one polished
half of the die is required. In addition, the average lifetime of the dies will last
longer, under mass production conditions, than usual because there is little wearing
off when forming with a fluid medium.
In order to get the most benefit out of this process a forming simulation should be
performed. This simulation may help to predict the maximal prestretching amount
achievable without damaging the sheet. The absence of friction between the blank
Chapter 7 - Page 28
Engineering Services, Inc.
and the conventionally used second half of the die makes the result of the
simulation very reliable. Furthermore, the process parameters, (e.g., preforming
pressure, etc.) could be easily adjusted.
7.5.3. Process Limitations
Depending on the grade of prestretching, which is related to the preforming
pressure, the size of the forming press (locking force) has to be chosen. This is
also influenced by the overall projected area of the part (e.g., for the ULSAB roof
panel, a press with a locking force of 4,000 was chosen.) A double (or triple) action
hydraulic press must be used to make the process reliable.
This press can be used for conventional forming, and with the use of some
additional equipment, for the tubular hydroforming process.
The filling time for the fluid medium pressure bed has to be taken into account as
well. This leads to a calculated cycle time for the ULSAB roof panel of about
30 - 40 seconds. Depending on the design of the part, this has to be compared to a
two-step conventional forming operation.
Due to potential die locking, it appears that an undercut on the hydroformed parts is
not feasible in this process without using a separate tool. This is also relevant for
the cutting of flanges. This has to be done separately using laser or conventional
trimming operations.
Chapter 7 - Page 29
Engineering Services, Inc.
7.5.4. Results
Roof panels for the ULSAB could be manufactured by using the active
hydromechanical sheet metal forming process. Different material qualities, like
isotropic, IF and bake-hardening types, were formed successfully. Due to the workhardening effect, which was applied through the above-described process, the sheet
thickness of the roof panel could be lowered to 0.7 mm, while the dent resistance
requirements were still met.
In order to limit the needed locking force of the press, the flange radii should be
designed not too small. The radii are directly related to the needed pressure during
the final forming operation, and if too small lead to an uneconomic high-locking
force/press size. The surface quality on the visible side of the ULSAB roof panel,
which was not in contact with any metal tool, was very high compared to
conventional formed (prototype) parts.
Chapter 7 - Page 30
Engineering Services, Inc.
8. Parts Manufacturing
Engineering Services, Inc.
8. Parts Manufacturing
8.1. Supplier Selection
The main criterion for supplier selection was quality. Although the process used
“soft” tools and lasers, the contract required production representative parts.
Therefore, it was decided to identify companies that specialize in one or more of the
following system groups:
•
•
•
•
•
Front End Structure
Floor Panels and Body Side Inner
Body Side Outer
Rear Structure
Roof and Roof Side Rails
Extensive discussions took place with approximately 30 suppliers on a worldwide
basis to identify the sources for the ULSAB program. The criteria used to
rationalize the final selections were:
•
•
•
•
•
•
•
Supplier must have major OEM quality rating or ISO 9000
Must be a system supplier to a major OEM
Must be prepared to enter simultaneous engineering prior to contract
release
CAD/CAM systems compatible with CATIA
Program management system established
Experience in match metal checks
Cost competitive
Chapter 8 - Page 1
Engineering Services, Inc.
Based on the foregoing, the following companies were selected:
•
•
•
•
•
Front End Structure – Stickel GMBH, leading supplier to Porsche AG
Floor Panels and Body Side Inner – Peregrine FormingTechnologies,
supplier to GM, Chrysler and Ford
Body Side Outer – AutoDie International, leading Body Side supplier to
Chrysler, also supplying Ford and GM
Rear Structure – Fab All Manufacturing, commodity supplier to Ford
Roof and Roof Side Rails – Schaefer Hydroforming
Number of Employees
Company Name
Address
Autodie International
44 Coldbrook, Grand Rapids, Michigan, USA
700+
Major products
Tools, Dies and Molds, Prototypes & Production
Automated Systems
Transfer Equipment
Welding Fixtures
Robotic Vision Systems
Other Divisions
Customers
Progressive Tool
WISNE Design
WISNE Design - Die Technology
WISNE Automation
Eagle Engineering
Freeland Manufacuturing
+ Others
Chapter 8 - Page 2
Ford
Chrysler
Tower
Spartanburg
Navistar
Cambridge
Major Equipment
GM
Jaguar
BMW
Karmax
Haworth
Presses up to 3000 t
Bed Size to 200 x 100
4 CMM
5 Axis Control Laser
1 Lamoine Machine System
CNC Mills
PDGS
CGS
CATIA
Engineering Services, Inc.
Company Name
Number of Employees
Address
Peregrine Forming Technologies 26269 Groesbeck, Warren, Michigan, USA
160
Major products
Prototype Tooling
Stampings and Assemblies
Doors Inner / Outer
Cowls, Fenders, Deck Lids
Roof Panels and Floor Panels
Other Divisions
Customers
APG - Technical Services
Battle Creek Stamping
Warren Stamping
Warren Assembly
Major Equipment
Ford
GM
Dana
Tower
Ogihara
Honda
Spartanburg
Presses up to 1500 t
Bed size to 192 x 79
3 CMM
5 Axis Control Laser
Foundry
3 CNC Mills
PDGS
CGS
CATIA
Number of Employees
Company Name
Address
Fab All Manufacturers
645 Executive Drive, Troy, Michigan, USA
95
Major products
Prototype Tools
Stampings and Assemblies
Specializing in Underbody, Front Structures
and Inner Structures
Other Divisions
Hubert Group
Sharp Mold Engine
M & T Design Services
Models & Tools
Customers
GM
Ford
Chrylser
AG Simpson
Veltri
Narmco
Major Equipment
Presses up to 1700 t
Bed size to 144 x 132
2 CMM
6 Axis Laser
NC Machining
CATIA
PDGS
CGS
Unigraphics
Chapter 8 - Page 3
Engineering Services, Inc.
Company Name
Address
Stickel GmbH
Porschestrasse 2, D - 74369 Loechgau
Number of Employees
40
Major products
Prototype Build
Prototype Tooling, Prototype Stampings
Low Volume Production Stampings and Subassemblies
Other Divisions
Customers
None
Audi
BMW
Mannesmann
Mercedes Benz
Opel AG
Porsche AG
Major Equipment
Presses up to 800 t
Bed sizes up to 2m x 3m
3D Laser
CMM Equipment
CATIA
CGS
Number of Employees
Company Name
Address
Schäfer Hydroforming, Schuler
Auf der Landerskrone 2, D - 57234 Wilhelmsdorf
135
Major products
Hydroforming Presses (Development, Fabricating)
Prototype and Production Parts
Technology Development (Active Hydro Mec)
Other Divisions
Customers
Tool Shop
FEM Forming Simulation
Hydroforming Componenets
Chapter 8 - Page 4
Audi
Aerosmith
GM
Benteler
Porsche
Major Equipment
Hydroforming presses to
3000t
10.000 t under Construction
High Speed Miling
Prebending Equipment
Engineering Services, Inc.
8.2 Simultaneous Engineering
In order to achieve the optimal design from a manufacturing and assembly
standpoint, reviews were held with the suppliers and the assembly facility to
evaluate all designs six months prior to design release.
Each supplier was represented by specialists in CAD/CAM, tool making and
manufacturing. Every detail was reviewed for formability, spring back issues,
aesthetic consideration, tolerance control and assembly issues. In addition to the
part suppliers, steel companies also attended these sessions in order to discuss
and resolve any material issues.
These reviews continued after design release, primarily in the suppliers’ facilities,
but in addition to the design for manufacture and design for assembly, the reviews
also included the supplier maintaining quality and timing plans.
8.3. Part Manufacturing Feasibility
Introduction
At the request of the ULSAB Steel Consortium and PES, Phoenix Consulting Inc.
has assisted in the investigation and documentation of the manufacturing feasibility
of the ULSAB components. The study includes the following objectives.
•
Demonstrate that the processes used to fabricate the ULSAB components
meet the following conditions:
, Used design intent materials.
, Can repeatedly produce parts that meet dimensional requirements.
, Can repeatedly produce parts that meet formability requirements.
•
Demonstrate that through continuous improvement, these processes can
be evolved to production capable processes.
, Mechanisms are in place and are being followed to address
manufacturing feasibility concerns.
, Action plans have been developed to address remaining barriers to
production capability.
Chapter 8 - Page 5
Engineering Services, Inc.
•
Demonstrate that state of the art methods and technologies have been
used to develop the demonstration hardware processes, such as:
, Forming Simulation.
, Early Steel Involvement.
, Dies and fixtures developed from CAD, CNC Machining and CMM
Inspection.
Overall Assessment
Although the components of the ULSAB body structure certainly present a
significantly greater challenge to production capability than a conventional design,
we are convinced that these components can be fabricated with production capable
processes under the following conditions:
1.The process of continuous improvement that has been undertaken by Porsche
is continued, including additional soft die tryout and minor product revision.
2.With the use of the more sophisticated press equipment that can be made
available in hard tool construction: Multiple Nitrogen Cushions, Toggle
Presses and with the superior surfaces encountered in hard tooling.
3.With the implementation of further enhancements in materials, blank
development and binder development.
The team assembled to fabricate these components has made excellent progress
along the learning curve of fabricating with high strength steel and laser welded
blanks, advancing the state of the art. The prototype processes have undergone
significant continuous improvement toward production capability
Documentation Overview
The components on the ULSAB body have been classified into three levels of
difficulty or criticality. Level C being the most critical, level B the next most critical
and all other parts are level A. The extent of documentation provided for a given
component has been determined accordingly. The purpose of these documents is
to validate the objectives outlined in the introduction. These documents have been
assembled into a notebook that can be provided through the ULSAB Consortium.
Chapter 8 - Page 6
Engineering Services, Inc.
These documents are described below, followed by a list of B and C level parts. In
the pages that follow is an example of the detailed summaries for each individual B
and C level part that can found in the notebook.
Level A - Non Critical
•
Material Characterization. This validates that the parts are made of
material that meets structural requirements and that these materials can
be worked into the forms of the respective parts.
Level B - Moderately Critical. All Level-A requirements plus the following:
•
•
•
Strain Analysis (Circle Grid and or Thickness Strain): Demonstrates that a
formability safety margin exists and that parts are not merely split free.
The goal and conventional buy off requirement is a 10% safety margin.
These Strain Analyses are the responsibility of the Steel Vendors as part
of the Early Involvement Program. They should include material properties
of metal used to form the evaluated panel and the associated press
conditions. This information is documented in AQP Parts format.
Process Set Up: After extensive tryout, die shops have arrived at, and
documented, optimum press conditions that will repeatedly yield quality
panels. These Press Conditions along with other details of die set up are
documented on Set Up Sheets. These Set Up Sheets can serve as
baseline for further continuous improvement to develop production capable
processes.
Part submission warrants: These certify that prototype parts meet
dimensional requirements.
Chapter 8 - Page 7
Engineering Services, Inc.
Level C - Most Critical: All level A and B requirements, plus the following.
•
•
•
•
CMM Reports: Computerized measurement of dimensional integrity.
Development Logs: Show that state of the art methods and technologies
were used to develop prototype processes and that these processes are
undergoing a continuous improvement of evolution toward production
capable processes.
Proposed Production Process: This is the capstone of the above efforts. It
is the culmination of lessons learned in prototype tryout and a
demonstration of Porsche’s confidence that the next step of setting up
production processes can be taken.
Forming Simulation: Finite Element Analysis based on CAD data was
used to identify formability concerns before the construction of tools.
B and C Level Parts
Part Name
Part Number
Die Shop
Level
040
Peregrine
C
Panel Rocker Inner
042 / 043
Peregrine
C
Panel B-Pillar Inner
064 / 065
Peregrine
C
Rail Rear Inner
046 / 047
Fab All
C
Rail Rear Outer
048 / 049
Fab All
B
Panel Wheelhouse Outer
070 / 071
Fab All
B
Panel Body Side Outer
060 / 061
Autodie
C
026
Stickel
C
Panel Skirt (& Shock Tower)
096 / 097
Stickel
C
Rail Front Inner
010 / 011
Stickel
B
Rail Front Extension
012 / 013
Stickel
B
Panel Dash
021
Stickel
B
Member Kick Up
091
Stickel
B
072 / 073
Schaefer
C
Panel Roof
085
Schaefer
B
Spare Tire Tub
050
Stickel
B
Pan Front Floor
Member Dash Front
Rail Side Roof
Chapter 8 - Page 8
Engineering Services, Inc.
Documentation
Forming Simulation
Strain Analysis
(Circle Grid, Thickness Strain)
Material Characterization
Process Set Up
(Set UP Sheets)
Proposed Production Process
Certification of Dimensional
Integrity (Warrant)
Inspection Report
Development Log. Demonstrates
state of the art procedures used to
develop capable prototype
processes & action plans for
making processes production
capable.
Observations and
Recommendations
Responsible
Format
Parts
Steel Co.
Steel Co. Report
Select Parts
Steel Co.
Steel Co.
and Phoenix
Steel Co, Die Shops
and Phoenix
Porsche & Phoenix
Die Shops
AQP
B&C
AQP
Phoenix Summary &
Die Shop Set Up Sheet
Process Sheet
Die Shop Form
A, B & C
Die Shops
CMM or Checking
Fixture Report
C
Die Shops
Die Shop Log
C
Phoenix
Phoenix Summary
B&C
B&C
C
B&C
Summaries of individual B and C level parts.
On the following pages you will find an example of the documented data. Included
will be:
1.Summary page, including observations and recommendations.
2.Part diagram.
3.Documentation checklist, listing and/or summarizing required documentation.
4.Material characterization sheet.
5.Forming limit diagram (part of strain analysis).
NOTE: Complete documentation for all A, B & C level parts is contained
In a separate report obtainable through the ULSAB Consortium.
Chapter 8 - Page 9
Engineering Services, Inc.
Pan Front Floor - 040
Part Manufacturing Feasibility Summary
The process involves first forming the front of the panel down, then the middle of
panel the down and finally the rear of the panel up. This had to be done in separate
operations for several reasons. One was press bed size. Another was the fact that
all these areas are on separate levels and proper control of metal cannot be
obtained without a more elaborate process involving nitro cushions and dydro units.
The availability of these resources for production will enable a reduction in the
number of operations, which will be necessary to reduce the total number of
operations once trim and flange dies are added. Trimming and flanging is currently
performed by laser and hammer form and will require cams in production due to the
orientation of some of the trim and flange lines.
Marginal strains detected in tryout and GD&T (geometric dimensioning &
tolerancing) issues would have to be reassessed after implementing the
recommendations below.
Recommendations Based on Documentation Checklist
Investigating grade change to a dent resistant steel that meets yield strength
requirements but has a higher n-value. A dry film lube trial is also recommended.
Consider use of a wider blank. This will allow for better control of metal outside of
the kickup area by adding a more gradual transition in the addendum and binder.
This may also enable the use of patches of higher formability metal where they are
needed the most. This exercise would be well worth the effort, considering the
portion of overall weight represented by the floor pan, and the challenging forming
characteristics associated with it.
Consider ways of forming embossed areas as late as possible in the process, either
by using restrike die or by delayed action in draw dies, to avoid metal locking on
and/or skidding over embossed area when it is required for feeding deep formations.
Forming Simulation of first draw predicted wrinkling in tunnel near kickup. This is
one of the areas where wrinkling was encountered in tryout.
Chapter 8 - Page 10
Engineering Services, Inc.
Marginal Forming Strains
at locations #2 and #15.
Second
Form
First
Form
#15
Third
Form
#2
Increase blank width
and implement smooth
transition & drawbar.
Embossments impede metal
flow; result in double draw lines.
Implement laser weld
for wider blank.
Chapter 8 - Page 11
Engineering Services, Inc.
ULSAB Part Manufacturing Feasibility Study
Documentation Checklist
Leve Part
l
#
Part Name
Supplier
Spc
Thk
Yield
Strength
Coating
Blank
C
Pan Frt Floor
Peregrine
0.7 mm
210 MPa
60G60GU
Rectangle
040
Document
Format
Status / Summary
Forming
Simulation
Steel Co
AQP
Material Test
Press
Conditions
Material Test
Final / Conam
Process Set
Up
LS-Dyna3D simulation of 1st draw predicted significant wrinkling in the step
area of part near the tunnel. This is one of the areas where wrinkling was
encountered in tryout. The other areas occurred mainly during subsequent
operations.
Reports 40_D1.TXF (First Form) & 40_D3.TXF (Third Form)
Safety Margin = 3%. Dry film lube trial suggested. Marginal Strains (#2,
#15) need to be re-assessed after implementing blank config, binder and
die process improvements.
Included in AQP. Also see Process Set Up below.
AQP
Samples shipped to Conam on 12/11/97
Peregrine
Proposed
Production
Process
Dimensional
Check
Dimensional
Check
Peregrine Set Up Sheet summary:
Blank Size = 1829mm x 2057mm
1) PreDraw = Three piece stretch forms tunnel and kickup
2) Draw = Single Action with Upr Binder on Nitro forms deep pocket at rear
of kickup 3) Three piece stretch forms shape at rear of panel 4) Flange.
Flange at kickup is hand formed. Would have to be Cam Flanged in
production. All trimming is by laser.
Form #1 Ram = 1000 ton Binder = 160 ton (40 cyl @ 1600 psi)
Lube = Quaker Prelube
Form #2 Ram = 400 ton Binder = 100 ton
Lube = Super Draw
Form #3 Ram = 400 ton Binder = 200 ton (toggle press)
Lube = Super Draw
1) Draw 2) 1st Trim 3) Re-strike 4) Form/Cam Form
5) Final Trim/Cam Trim
Warrant
Included
CMM Report
CMM detected points that deviated from nominal by more than +/- 0.5 mm,
however all were vertical and attributable to part length and flexibility, or
hammer formed flanges. No difficulty experienced in assembly.
Simultaneous Engineering procedures were used to develop the process,
and continuous improvement was implemented to evolve the process
toward production capability. Supplier concerns were fed back to Porsche
and product revisions were subsequently implemented. Summary of
development history and log of product changes is included. Also included
is sketch of part showing significant manufacturing related changes.
Strain
Analysis
Development
Log
Chapter 8 - Page 12
Engineering Services, Inc.
Chapter 8 - Page 13
Engineering Services, Inc.
Chapter 8 - Page 14
Engineering Services, Inc.
Chapter 8 - Page 15
Engineering Services, Inc.
8.4. Quality Criteria
The quality assurance system utilized on the ULSAB project followed the same
standards as normal automotive practices. The key elements of control were:
•
•
•
•
•
Material
Engineering levels
Process control
Dimensional accuracy
Parts submission
Material: All material received was checked for dimensional accuracy by the part
suppliers, the steel suppliers provided the material characterization data which was
verified by an independent laboratory. Additionally, Porsche checked the material
for weldability.
Engineering Levels: A strict engineering change control system was implemented
for this program. At each weekly review meeting all product levels were checked
against the design status to insure compatibility. Suppliers were not allowed to
implement any change without the authorization of PES.
Process Control: As previously stated, the components were produced to
production intent standards. Therefore, to insure this occurred, regular audits of the
process were undertaken.
Dimensional Accuracy: For each component, automotive standard checking fixtures
were produced. These fixtures were used throughout the development process to
provide verification of dimensional accuracy. Additionally for all major parts, the
contract with the suppliers called for two fully CMM checked samples. As further
assurance, where possible, match checks were undertaken to insure fit and function
for the assembly process.
Parts Submission: The approval process was based on PPAP (Production Part
Approval Process) as outlined in QS 9000 guidelines. Before any part was shipped,
the supplier had to provide documentation that showed all material, engineering,
process and dimensional controls had been completed and met with the
specifications set within the program.
Chapter 8 - Page 16
Engineering Services, Inc.
9. DH Build
Engineering Services, Inc.
9. DH Build
9.1. Introduction
After ULSAB Phase 1 was successfully completed, the ULSAB Consortium decided
to proceed with the ULSAB program into Phase 2. This involved proceeding from a
conceptual study to the real world hardware, whereby the predicted mass savings
and improved performance could be proven by actual product.
Due to the experience in laser welding, Porsche’s R & D Center in Weissach,
Germany was chosen for the execution of the 13 DH builds.
Figure 9.1-1 Prototype Shop
Chapter 9 - Page 1
Engineering Services, Inc.
9.2. Joining Technologies
9.2.1. Laser Welding
For more than 10 years the laser has shown its production capability. The first auto
body application was the blank welding of the floor panel for the Audi 100. Laser
welding in the assembly process was first brought into a production plant by BMW
for the roof welding of its former touring model 3 series and Volvo for the roof
welding of the 850 model.
Since then, especially during the last three years, an increasing number of auto
manufacturers have installed laser welding equipment within their production lines.
Today laser welding applications in production plants are utilized all over the auto
body, such as the front end, under body, closure panels and roof panel.
Roof
Roof
• Audi
• BMW
• Ford
• Audi
• BMW
• Ford
• GM
•
Mercedes
• Opel
• GM • Mercedes
• Opel
• Renault
•
Volvo
• Renault • Volvo
• Volkswagen
• Volkswagen
B/C
B/CPillars
Pillars
• Audi
• Mercedes
• Audi
• Mercedes
Decklid
Decklid/ Tailgate
/ Tailgate
• BMW
• Daihatsu
• BMW
• Daihatsu
• Honda
•
• Suzuki
• HondaOpel
• Opel
• Suzuki
• Volkswagen
• Volkswagen
Hood
Hood
• Opel
• Volvo
• Opel
• Volvo
Doors
Doors
• Honda
• Porsche
• Honda
• Porsche
Front
Structures
Front
Structures
• BMW
• Mercedes
• BMW
• Mercedes
Laser welding applications on production auto-bodies
Fig. 9.2.1-1 Laser Welding in Assembly
Chapter 9 - Page 2
Engineering Services, Inc.
The major reasons for using laser welding is the predominantly high static and
dynamic strength of the joints, one side weld access for the welding equipment,
small thermic impact zone and good aesthetic look at the joint area. The total
length of the laser welding seams for the assembly on the demonstration hardware
is 18.28 meters.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Rail Front Outer to Rail Front Inner
Rail Fender Support Inner to Rail Fender Support Outer
Panel Body Side Outer to Panel A-Pillar Inner Lower
Rail Fender Support Outer to Panel Body Side Outer
Panel B-Pillar Inner to Rail Side Roof
Bracket Member Pass Through Lower to Member Pass Through
Panel Wheelhouse Inner to Rail Side Roof
Panel Back to Rail Rear Inner and Rail Rear Outer
Panel Dash to Rail Front Extension
Panel Cowl Upper to Panel A-Pillar Inner Lower
13
14
15
16
17
(12)
18
19
(14)
(3)
10
11
12
20
9
7
5
1
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
2
3
4
Panel B-Pillar Inner to Panel Rocker Inner
Panel Roof to Panel Body Side Outer
Rail Side Roof to Panel A-Pillar Inner Upper
Panel Body Side Outer to Rail Side Roof
Panel Package Tray Upper to Support Package Tray
Support Panel Rear Header to Rail Side Roof
Panel Roof to Rail Side Roof
Member Pass Through to Brkt Member Pass Through Upr Frt & Rear
Rail Rear Outer to Rail Rear Inner
Panel Package Tray Upper to Panel Gutter Decklid
Figure 9.2.1-2 Laser Welding on ULSAB Demonstration Hardware
Chapter 9 - Page 3
6
8
Engineering Services, Inc.
9.2.2. Spot Welding
Spot welding is for all OEMs a well-experienced, reliable, affordable joining
technique for steel auto bodies, even with zinc-coated steel materials. Porsche, for
example, has been producing cars since 1977 with 100% zinc coated steel sheet
metal and was the first company in the world practicing this. Now, more and more
OEMs are switching to 100% zinc coated materials to improve corrosion protection
and to give a long time anti-corrosion guarantee. Also for ULSAB, 100% of the
material is double side zinc coated.
control
unit
power
unit
transformer
current measurement
voltage measurement
Figure 9.2.2-1 Configuration of a Welding System
Porsche’s R & D Center Body Assembly Facility utilizes computer controlled
medium frequency (1000 Hz) welding equipment. This system uses calibration to
ensure that the welding current is maintained at a constant level. Thereby providing
a good weld without disturbances and achieving optimum settings for welding time,
welding current and electrode force. Having established the optimum setting, the
data is stored in the computer enabling the use of the ‘control mode’ to ensure all
subsequent welding operations achieve the same optimum integrity.
Chapter 9 - Page 4
Engineering Services, Inc.
These control processes inevitably necessitate fast welding current sources. This
requirement is fulfilled by medium frequency inverters with a response time of one
millisecond at an inverter frequency of 1000 Hz and by the substantially faster
transistor DC technology.
weld current
weld current
AC welding operation (50 Hz)
medium frequency
inverter welding operation
(1000 Hz)
Comparison of the control response of thyristors and inverter controllers
Figure 9.2.2-2
The system is sensitive to:
•
•
•
•
•
•
•
main voltage fluctuations
shunts
electrode wear (automatic stepper function)
electrode force fluctuations
small edge distances
welding splashes
changes from two sheet to multiple sheet welds
Chapter 9 - Page 5
Engineering Services, Inc.
The control process compensates the various influencing factors by increasing or
reducing the current strength and extending the welding time. Extension of the
welding time can be limited.
Welding splashes are monitored via output of an error message, with optional
shutdown of the welding current.
Optimum adaptation to each weld spot guarantees that the required strength for
weld joints is maintained throughout broad ranges.
Figure 9.2.2-3 Medium Frequency Spot Welding Equipment
Spot welding is used on ULSAB in all areas with suitable weld access and normal
structural loads.
The assembly of the demonstration hardware uses 2,126 spot welds.
Chapter 9 - Page 6
Engineering Services, Inc.
9.2.3. Active Gas Metal Arc Welding (MAG)
Active Gas Metal Arc Welding, or similar joining techniques, is used at all OEMs in
locations with no weld access for spot welding or in areas with high stresses due to
its strong structural behavior in comparison to spot welding.
The disadvantages of this process, like slow welding speed, big heat impact zone,
and pollution by weld fumes, especially with zinc coated materials, forced many
OEMs to reduce it to a minimal amount.
The targets for ULSAB were established to minimize the MAG welding seams.
MAG welding is only used on the ULSAB body structure at locations without weld
access for spot and laser welding.
In total, there are 1.5 meters of MAG welding on the DH structure.
4 1
3
5
2
1.
2.
3.
4.
5.
6.
7.
6 7
Panel A-Piller Inner Lower to Panel Cowl Upper
Door Hinges to Panel Body Side Outer
Door Hinges to Panel B-Pillar Inner
Door Hinges to Panel A-Pillar Inner
Support Package Tray to Rail Side Roof
Bracket Roof Rail Mount to Rail Side Roof
Bracket Member Pass Through Lower to Rail Side Roof
Figure 9.2.3-1 MAG Welding on ULSAB Demonstration Hardware
Chapter 9 - Page 7
Engineering Services, Inc.
9.2.4. Adhesive Bonding
The ULSAB steel sandwich material cannot resist the high temperatures during the
painting process for body structures. Therefore this material is only suitable for
parts which are assembled to the body after the painting procedure. Another factor
is the non-weldability of the ULSAB sandwich material.
So for the two parts on ULSAB made of steel sandwich adhesive bonding is the
chosen joining technology.
It has not only a structural function, it also provides sealing. The two panels made
from steel sandwich material are the Panel Dash Insert (Part No. 022) and the
Panel Spare Tire Tub (Part No. 050).
Figure 9.2.4-1 Bonding at Panel Dash Insert
Chapter 9 - Page 8
Engineering Services, Inc.
In the production line, the panel dash insert will be assembled to the painted body
structure as part of the instrument panel module. This includes the instrument
panel, steering column, air conditioning system and pedal system. The panel dash
insert is adhesive bonded and additionally bolted to dash panel. The bolting is
necessary to keep the part in position until the bonding material is hardened.
The panel spare tire tub will be assembled to the painted body structure as a
module including the spare tire and the repair tools. The module is bonded to the
structure. The operation does not require additional fixturing.
The bonding material is a two component, non-conductive, high modulus, high
viscous, chemically-curing polyurethane adhesive/sealant that cures almost
independently of temperature and moisture. It is Betaseal X 2500 produced by
Gurit Essex.
Figure 9.2.4-2 Bonding at Panel Spare Tire Tub
Chapter 9 - Page 9
Engineering Services, Inc.
Technical Data
Basis
Polyurethane prepolymer
Color
black
Solids content
>98%
(GM 042.0)
Flash Point
Processing temperature
Working time
>100° C
ideal 10° C - 35° C
approx. 10 min. at 23° C/50% r.h.
(Processing time)
Sagging behavior
Ultimate tensile strength
good, non-sagging
> 5.5 MPa
(DIN 53 504)
Percentage elongation
> 200%
(DIN 53 504)
Combined tension (GM 021)
> 4.5 MPa
and shear resistance
G-Modulus
Specific electrical
> 2.5 MPa
> 10
W cm
(volume resistivity)
Abrasion resistance
Recovery (DIN 52 458)
Extremely high
approx. 99%
Temperature stability
- 40° C at 100° C (for short periods up to 140° C)
Resistance to chemicals
Highly resistant to aqueous chemicals, petrol
(in cured conditions) alcohol and oils.
Conditionally resistant to esters, aromatics and
and chlorinated hydrocarbons.
Preparation of bonding surface
All bonding surfaces must be free of dirt, dust,
water, oil and grease. In general, surfaces
should be primed.
Chapter 9 - Page 10
Engineering Services, Inc.
9.3. Flexible Modular Assembly Fixture System
The body shop in Porsche’s R & D Center used a highly flexible modular fixture
system for the DH assembly. It is based on standardized units, which are
adjustable in all directions.
Figure 9.3-1 Assembly Fixture Module
There are many advantages of this fixture system. 95% of the elements in a fixture
are from the standardized module system and can be used also for other car
programs.
Chapter 9 - Page 11
Engineering Services, Inc.
Figure 9.3-2a Assembly Fixture Module Detail
Figure 9.3-2b Assembly Fixture Module Detail
Chapter 9 - Page 12
Engineering Services, Inc.
The fixture design performed in CATIA was very efficient, because all models were
accessible from the CAD data bank. Therefore, the construction time for assembly
fixtures was reduced and modifications or corrections of existing assembly fixtures
could be implemented rapidly.
Figure 9.3-3 Assembly Fixture - Bodyside Inner Subassembly
Chapter 9 - Page 13
Engineering Services, Inc.
Porsche is using the flexible modular system in two ways.
The first is the so-called shuttle system, which is related to the set-up pallets. The
shuttles for different assemblies are stored in a shuttle magazine. During the
assembly operation the shuttle is fixed on a set-up pallet. The changeover of
various assembly shuttles on a set-up pallet is a very fast process. These
assembly shuttles are mobile and can be used at different locations.
Figure 9.3-4 Assembly Fixture Shuttle on Setup Pallet
Chapter 9 - Page 14
Engineering Services, Inc.
The second method is the utilization of a rolling device that supports the modular
assembly fixtures independent from set-up pallets. These assembly fixtures work at
any location.
Figure 9.3-5 Mobile Assembly Fixture - Shock Tower Front SubAssembly RH/LH
Chapter 9 - Page 15
Engineering Services, Inc.
9.4. Design of Assembly Fixtures
All fixtures are developed with a CAD system (CATIA) based on the existing design
data. The CAD data models of the fixture system modules are available from a data
bank.
Figure 9.4-1 Fixture Development on CAD System
Figure 9.4-2 CAD Data Modules of Fixture System
Chapter 9 - Page 16
Engineering Services, Inc.
The DH assembly sequence is exactly the same as it is foreseen in the production
plant. Due to the fact that in prototype productions no cycle time limit is given one
fixture can be used for more joining operations than in a production line. This
results in a drastically reduced number of assembly fixtures in relation to a
production line.
For the ULSAB assembly, the Porsche body shop used the following fixtures:
•
•
•
•
•
•
Assembly
Assembly
Assembly
Assembly
Assembly
Assembly
Shock Tower Front
Front End
Floor Complete
Under Body Complete
Body Side Inner
Body Complete
An example of a fixture design is shown in Figure 9.4-3.
Figure 9.4-3 Fixture Shock Tower Front
Chapter 9 - Page 17
Engineering Services, Inc.
9.5. DH Build
9.5.1. Assembly Team
The Porsche BIW assembly team consists of the following personnel:
•
•
•
1 foreman
1 expert/deputy foreman
23 workers which include 5 with foreman’s / technician’s degree and 5
workers trained for CATIA
Figure 9.5.1-1 Body Shop
Chapter 9 - Page 18
Engineering Services, Inc.
In a workshop space of 1200 m2, the following equipment is installed:
•
•
•
•
•
12 setup pallets (6x3m) with surface measuring device
4 mobile welding machines, 1000 Hz with control equipment
5 mobile welding machines, 50 Hz with constant-voltage regulation system
5 overhead spot-welding devices with 3 secondary guns each and a 50 Hz
Bosch control system
1 Rofin Sinar Laser device, 2.5 kW
Two applications with special interest for ULSAB will be described in more detail.
All spot welds on ULSAB were manufactured with a mobile Duering welding cart
and a Matuschek medium-frequency inverter device with master control system.
Figure 9.5.1-2
Chapter 9 - Page 19
Engineering Services, Inc.
The welding gun changeover system allows a rapid change between different types
of welding guns, whereby a special gun coding provides the correct weld
parameters from an automatic program selection.
Figure 9.5.1-3 Weld Gun Station
Chapter 9 - Page 20
Engineering Services, Inc.
The laser welding and laser cutting cabin is equipped with a KUKA KR 125 robot.
The maximal load is 125 kg and the working range of 2410 mm.
Figure 9.5.1-4 Laser Cabin
Chapter 9 - Page 21
Engineering Services, Inc.
The laser source is a Rofin Sinar CW 025 Nd:YAG Laser. The maximum output of
2500 W is transferred through a switching device with two outlets via two 15-m
glass fibre cable of 0.6 mm diameter to the laser optic.
Figure 9.5.1-5 Laser
Besides a laser cutting head three different types of laser welding heads are
available.
Figure 9.5.1-6 Laser Picker
Chapter 9 - Page 22
Engineering Services, Inc.
Figure 9.5.1-7 Single Roller
Figure 9.5.1-8 Double Roller
Chapter 9 - Page 23
Engineering Services, Inc.
9.5.2. Build of the Test Unit
The construction of the test unit, internally called “workhorse,” started on May 26,
1997, and began testing on June 27, 1997.
The following series of photographs shows steps of the assembly sequence of the
test unit.
Due to the extensive preparations, the construction worked out excellent, but there
was still room for small improvements.
Figure 9.5.2-1 Rear Floor Subassembly
Chapter 9 - Page 24
Engineering Services, Inc.
Figure 9.5.2-2 Subassembly Front End
Figure 9.5.2-3 Subassembly Underbody Complete
Chapter 9 - Page 25
Engineering Services, Inc.
Figure 9.5.2-4 Subassembly Body Side Inner
Figure 9.5.2-5 Assembly Body Side Inner to Underbody
Chapter 9 - Page 26
Engineering Services, Inc.
Figure 9.5.2-6 Subassembly Body Side Inner with Underbody
Figure 9.5.2-7 Sub-Assembly Body Side Outer, with Body Side Inner and Underbody
Chapter 9 - Page 27
Engineering Services, Inc.
9.5.3. Build of DH #2 to DH #13
After build and testing of the test unit, a design review meeting in Porsche’s R & D
Center was held with the experts in the fields of body design, safety, CAE
calculations, parts manufacturing and body assembly. Ideas for improvements in
respect to performance, parts feasibility, weld access and appearance were
generated in this meeting.
The next step was a redesign of the ULSAB body structure reflecting the ideas of
the design review meeting. The CAE calculations of the changed FE model proved
nearly the same performance. Now new parts were manufactured incorporating
these changes in the construction of DH #2 to DH #13.
Figure 9.5.3-1 Demonstration Hardware #2 in Body Shop
The build of DH #2 started on December 1, 1997. The assembly sequence for DH
#2 to DH #13 remained the same as test unit.
Chapter 9 - Page 28
Engineering Services, Inc.
9.6. Quality
9.6.1. Body Quality Control Team
The Porsche Body Quality Control Team includes the following personnel:
•
•
•
•
1
2
5
2
engineer
technicians
foremen
specialist workers
In a working area of 300 m2 the following equipment is used for body quality control
measurement:
•
•
•
1 Stiefelmeyer double-column coordinate measuring machine (CMM)
1 Stiefelmeyer single-column manual measuring machine
1 Zeiss double-column CMM
Figure 9.6.1-1 DH #2 during Measuring Procedure
Chapter 9 - Page 29
Engineering Services, Inc.
The general range of services includes:
•
•
•
•
•
•
Part acceptance at supplier’s premises
Model acceptance at supplier’s premises
Body measurement
Digitalization of data for design
Trouble-shooting
Prototype quality statistics
9.6.2. Quality Control Measurements of DHs
The basis for part and assembly quality was the early involvement of all relevant
participants in the design and engineering process. Regularly simultaneous
engineering meetings were established with designers, engineers, material
suppliers, tool and part manufacturers and body shop personnel.
The expert group defined locator holes, tooling holes and fixing points. To ensure
excellent quality, these defined points were used for the complete process chain
from parts manufacturing over subassemblies to final assembly.
All manufactured parts were inspected by the supplier’s quality control personnel
and approved by Porsche specialists.
The first proof of feasibility and design for manufacture was the successful
construction of the test unit. This demonstration hardware was fully inspected by
Porsche’s quality control team. In total, about 200 different points on the ULSAB
body structure were measured and compared to the original CAD data.
The measured dimensions were, especially for a first time assembled body
structure, in a close range to the nominal values.
Chapter 9 - Page 30
Engineering Services, Inc.
Figure 9.6.2-1 Measuring protocoll
Nevertheless, the results of the test unit were used to develop modifications of the
tools for part manufacturing and of the assembly fixtures for improved quality,
meaning smaller tolerances for the following DHs. Each DH is or will be inspected
to evaluate a quality statistic for the ULSAB program.
Chapter 9 - Page 31
Engineering Services, Inc.
9.7. Conclusion
The assembled demonstration hardware proved to be a successful execution of the
body structure construction. The measured tolerances are in a comparable range in
relation to average car programs.
The challenges of laser welding in assembly, assembly of hydroformed parts, 90%
high strength steel, and steel sandwich material, were mastered. The principle
condition for success was the simultaneous engineering process. All project
partners contributed to the realization of Phase 2 of the ULSAB program.
Through early involvement in the project, all parties involved incorporated all of their
expertise into the realization of the demonstration hardware.
Figure 9.7-1
Chapter 9 - Page 32
Engineering Services, Inc.
10. Testing and Results
Engineering Services, Inc.
10. Testing and Results
10.1. Scope of Work
To prove the structural integrity of the ULSAB demonstration hardware, the following
test procedures were executed as part of the ULSAB program in Phase 2.
•
Static rigidity
• Static torsion
• Static bending
•
Modal analysis
• 1st Torsion mode
• 1st Bending mode
• 1st Front end lateral mode
•
Mass
• DH mass in test configuration
All testing work was performed at Porsche’s R & D Center in Weissach.
Fig 10.1-1 Aerial View
Chapter 10 - Page 1
Engineering Services, Inc.
10.2. Targets
The main factors affecting the ride and handling of the vehicle are Noise, Vibration
and Harshness, known as NVH behavior. To achieve the desired levels of comfort
for the occupants, the vehicle body must have high static and dynamic rigidity. In
other words, the auto body should have high stiffness. This is required because the
increased rigidity improves the vehicle resistance to excitement caused by the drive
train, the engine or by road conditions such as bumps and potholes. When excited,
the car body vibrates at particular frequencies, called its natural frequencies, and
also in a particular manner called its mode shape. The mode shapes are for
instance on: global torsion mode, global bending mode and front end lateral mode.
Another result of good rigidity would be minimal deviations in the dimensions of the
body structure openings such as the hood, front door, rear door and deck lid under
load conditions. These movements between the body structure and the closure
panels often create sounds.
Furthermore, it should be proven that the received numbers from the analysis by
FE-calculations are in correlation with the results gathered by the testing procedure.
Based on the current average of selected, benchmarked vehicles in Phase 1, the
following targets for the ULSAB structure were established:
Performance
Mass
Static torsional rigidity
Static bending rigidity
First body structure mode
Targets
[ 200 kg
m 13,000 Nm/deg
m12,200 N/mm
m 40 Hz
NOTE: Structural performance with windshield and backlight; mass
without windshield and backlight.
Chapter 10 - Page 2
Engineering Services, Inc.
10.3. Static Rigidity
10.3.1. Test Setup
10.3.1.1. General
The DH in full test configuration consists of the following parts:
•
•
•
•
•
•
•
•
•
•
Welded Body Structure
Bonded Windshield and Back Light
Bonded and bolted Panel Dash Insert (Part-No. 022)
Bonded Panel Spare Tire Tub (Part-No. 050)
Bolted Reinforcement Panel Dash Brake Booster (Part-No. 115)
Bolted Braces Radiator (Part-No. 188)
Bolted Reinforcement Radiator Rail Closeout RH/LH (Part -No. 094/095)
Bolted Reinforcement Radiator Support Upper (Part-No. 001)
Bolted Tunnel Bridge Lower/Upper
Bolted Brace Cowl to Shock Tower Assembly
Figure 10.3.1.1-1 DH with Bonded / Bolted Parts
Chapter 10 - Page 3
Engineering Services, Inc.
The unpainted body structure was measured without front and rear suspension
system. The body structure was held at four points: the front; at Panel Skirt RH/LH
(Part-No. 096/097) and the rear; at Plate Rear Spring Upper (Part-No. 110).
Along the front rails, the rockers, and the rear rails 12 stadia rods were attached.
Twenty-four electronic feelers measured the movements of these rods.
Aluminum panels with glass thickness were used to simulate the bonded windshield
and backlight. Due to the fact that the related material property for rigidity and
stiffness, the Youngs modulus, shows a close similarity for glass and aluminum.
This can be done without compromising the test results, but taking advantages in
timing and cost.
10.3.1.2. Static Torsion
The DH was mounted to the test rig with rigid tubes. Two rear locations at the plate
spring rear upper were constrained, while the load was applied to panel skirt RH/LH
by a scale beam.
Figure 10.3.1.2-1 Test Configuration for Static Torsion
Chapter 10 - Page 4
Engineering Services, Inc.
The measurements were taken with four different loads from M =1000Nm to
t
M max=4000Nm.
t
Before starting the measuring procedure, the maximum load was applied to the DH
to eliminate the sag rate.
10.3.1.3. Static Bending
The DH was mounted to the test rig by rigid tubes. The four fixing points of the DH
were constrained.
The loads were applied to the center of the front seats and to the center of the two
outer rear seats.
Figure 10.3.1.3-1 Test Configuration for Static Bending
The measurements were taken with four different loads from F = 1000 N
b
(4 x 250 N) to F max = 4000 N (4 x 1000 N).
b
Before starting the measuring procedure, the maximum load was applied to the DH
to eliminate the sag rate.
Chapter 10 - Page 5
Engineering Services, Inc.
10.3.2. Results
10.3.2.1. Static Torsion
Figure 10.3.2.1-1 DH on Test Rig for Static Torsion
The torsional rigidity for the test unit in the configuration described in section
10.3.1.1 is:
With glass
Without glass
Chapter 10 - Page 6
21,620 Nm/deg
15,790 Nm/deg
Engineering Services, Inc.
Test Unit Displacement Torsion
20
Rear Axle
Front Axle
Angle of Twist [min]
15
4000 Nm
3000 Nm
2000 Nm
1000 Nm
10
5
0
-5
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
Longitudinal Axis X [mm]
Figure 10.3.2.1-2 Torsion Lines 4 Load Cases with Glass
In general, the graph plot is running harmonic. There is only a jump in rigidity
between x = 3800 to x = 4200. This is related to the positive impact of the Member
Pass Through (Part-No. 090) to the torsional stiffness.
Test Unit Gradient Torsion
0.4
Gradient [°/m
Rear Axle
Front Axle
0.3
0.2
0.1
0
-0.1
-0.2
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
Longitudinal Axis X [mm]
Figure 10.3.2.1-3 Gradient of Torsion Line with Glass
The above graph shows the gradient of the torsion line. The disharmonies of the
torsion line can be seen in a higher resolution.
Chapter 10 - Page 7
Engineering Services, Inc.
The torsional rigidity for DH #2 in the configuration described in section 10.3.1.1 is:
With glass
Without glass
20,800 Nm/deg
15,830 Nm/deg
DH #2 Displacement Torsion
20
Rear Axle
Front Axle
4000 Nm
3000 Nm
2000 Nm
1000 Nm
Angle of Twist [min]
15
10
5
0
-5
500
1000
1500
2000
2500
3000
3500
4000
4500
Longitudinal Axis X [mm]
Figure 10.3.2.1-4 Torsion Lines 4 Load Cases with Glass
As expected, the results are very close to the test unit.
This assumption is based on the test results without glass, because these are
nearly identical (15,790 Nm/deg vs. 15,830 Nm/deg).
Chapter 10 - Page 8
5000
Engineering Services, Inc.
DH #2 Gradient Torsion
0.4
Rear Axle
Front Axle
0.3
Gradient [°/m]
0.2
0.1
0
-0.1
-0.2
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
Longitudinal Axis X [mm]
Figure 10.3.2.1-5 Gradient of Torsion Line with Glass
The above graph shows the gradient of the torsion line. The disharmonies of the
torsion line can be seen in a higher resolution.
Chapter 10 - Page 9
Engineering Services, Inc.
To investigate the impact of several bonded and/or bolted parts, additional
measurements in various test configurations were undertaken with the test unit.
Test Configurations:
1.
2.
3.
4.
5.
Full configuration as described in Section 10.3.1.1
As 1, but without braces radiator (Part-No. 188)
As 2, but without radiator support upper (Part-No. 001/094/095)
As 3, but without bolted brace cowl to shock tower assembly
As 4, but without tunnel bridge
Torsion Rigidity
Torsion Rigidity [%]
110
100
100.0
98.3
98.3
90
92.0
92.0
4
5
80
1
2
3
Test Configuration
Figure 10.3.2.1-6 Torsion Rigidity Five Test Configurations
As the numbers show, only the bolted brace cowl to shock tower assembly has a
significant impact on the torsional rigidity of 6.3%.
Chapter 10 - Page 10
Engineering Services, Inc.
10.3.2.2. Static Bending
Figure 10.3.2.2-1 DH on Test Rig for Static Bending
The bending rigidity of the test unit in the configuration described in Section
10.3.1.1 is:
With glass
Without glass
20,460 N/mm
17,150 N/mm
Chapter 10 - Page 11
Engineering Services, Inc.
Test Unit Displacement Bending
0.5
Rear Axle
Front Axle
0.4
Vertical Displacement [mm]
0.3
0.2
0.1
0
-0.1
-0.2
4000 N
3000 N
2000 N
1000 N
-0.3
-0.4
-0.5
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
Longitudinal Axis X [mm]
Figure 10.3.2.2-2 Bending Lines 4 Load Cases with Glass
The graph is running harmonic. There is only a local increase in bending rigidity
between x = 3500 and x = 4200. This indicates a stiff joint between rocker and rear
rails. Furthermore, Porsche relates this to the design of the side roof rail.
Test Unit Average Deviation Bending
Deviation from the average [%]
50
Front Axle
40
Rear Axle
30
20
10
0
-10
-20
-30
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
Longitudinal Axis X [mm]
Figure 10.3.2.2-3 Deviation from the Average Bending Line with Glass
The above graph shows the deviation from the average value of the bending line.
The disharmonies can be seen in a better resolution.
Chapter 10 - Page 12
Engineering Services, Inc.
The bending rigidity for DH #2 in the configuration described in Section 10.3.1.1 is:
With glass
Without glass
18,100 N/mm
15,950 N/mm
DH #2 Displacement Bending
0.5
Rear Axle
Front Axle
Vertical Displacement [mm]
0.4
0.3
0.2
0.1
0
-0.1
-0.2
4000 N
3000 N
2000 N
1000 N
-0.3
-0.4
-0.5
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
Longitudinal Axis X [mm]
Figure 10.3.2.2-4 Bending Lines 4 Load Cases with Glass
The bending lines show the same characteristics as for the test unit, but the
absolute value decreased by 11%. The local increase between x=3500 and x=4200
is not so evident as it was on the test unit. This could be created by local
modifications of the side roof rail and the rear rails for improved manufacturing.
Furthermore, the material gage of the panel roof changed from 0.77mm to 0.70mm
due to material availability problems for the test unit; this was also a factor for the
decrease of the absolute value.
Additionally Porsche has experienced that static rigidities of body structures differ
by plus/minus five percent (5%) even under series production conditions.
Chapter 10 - Page 13
Engineering Services, Inc.
DH #2 Average Deviation Bending
50
Deviation from the average [%]
40
Front Axle
Rear Axle
30
20
10
0
-10
-20
-30
-40
-50
500
1000
1500
2000
2500
3000
3500
4000
4500
Longitudinal Axis X [mm]
Figure 10.3.2.2-5 Deviation from the Average Bending Line with Glass
The above graph shows the deviation from the average value of the bending line.
The disharmonies can be seen in a better resolution.
Chapter 10 - Page 14
5000
Engineering Services, Inc.
To investigate the impact of several bonded and/or bolted parts, additional
measurements were undertaken:
Test Configurations:
1.
2.
3.
4.
5.
Full configuration as described in Chapter 10.3.1.1
As 1, but without braces radiator (Part-No. 188)
As 2, but without radiator support upper (Part-No. 001/094/095)
As 3, but without bolted brace cowl to shock tower assembly
As 4, but without tunnel bridge
Bending Rigidity [%]
Bending Rigidity
110
100
100.0
100.0
99.0
98.8
1
2
3
4
100.0
90
80
5
Test Configuration
Figure 10.3.2.2-6 Bending Rigidity Five Test Configurations
As the numbers show, none of these parts display a significant impact on bending
rigidity.
The increase from test configuration four (4) to test configuration five (5) is caused
by local effects of the tunnel bridge to the displacement of the rocker. This behavior
was also noticed in other body structures.
Chapter 10 - Page 15
Engineering Services, Inc.
10.4. Modal Analysis
10.4.1. Test Setup
A modal analysis describes the vibration behavior of a structure. Results of a modal
analysis are the resonance frequencies of the specific structure and the
corresponding mode shapes (how the structure vibrates).
The ULSAB structure was suspended on a test rack held by rubber straps to
decouple the test unit from the supporting structure of the test rack.
In order to find the mode shapes and the resonance frequencies, energy is applied
to the structure. The response of the structure (in general the acceleration at
different points) is measured in relation to the input forces. From the contribution of
each input force to each response value, the dynamic behavior of the structure is
calculated.
Figure 10.4.1-1 Test Configuration for Modal Analysis
In the case of the ULSAB, the body structure is excited by means of four
electrodynamic shakers that are coupled to the corner points of the structure.
Chapter 10 - Page 16
Engineering Services, Inc.
The simultaneous excitation with four shakers is necessary to provide good energy
distribution into the structure and to minimize the influence of possible nonlinearities
to the quality on the results. In addition, the torsion and bending modes of the body
can be excited definitely. Torsion and bending are the most important global modes
of a body structure.
Each of the four shakers is driven by a computer-generated, statistical independent
band limited (0 to 100 Hz) Gaussian random noise spectrum. The response of the
structure is determined by measuring vibration transfer functions between the
acceleration at each measurement point in three orthogonal directions and each
driving force.
Accelerometer
HP 9000/700
LMS CADA-X
DAC Interface
ADC Interface
Memory
Electrodynamic
Shakers
Power Amplifier
Charge
Amplifier
Aliasing Filter
and Amplifier
Figure 10.4.1-2 Set-Up for Modal Analysis
The global parameters of the structure, frequency and damping are determined
thereafter by a Least Squares Complex Exponential (LSCE) fitting.
Chapter 10 - Page 17
Engineering Services, Inc.
The modal displacement is calculated subsequently by fitting a Multiple Degree of
Freedom (MDOF) model to the transfer functions in the time domain.
The test configuration of the test unit was exactly the same as the testing of static
rigidities described in section 10.3.1.1.
10.4.2. Results
Figure 10.4.2-1 DH on Test Rig for Modal Analysis
Chapter 10 - Page 18
Engineering Services, Inc.
The global modes of the test unit in the described test configuration can be seen in
the following chart:
Test Unit Modal Analysis
First Modes [Hz]
70
60
60.6
60.8
62.4
64.3
60.6
50
49.1
40
Torsion
Bending
without glass
Front End Lateral
with glass
Figure 10.4.2-2 Modal Analysis Results - Test Unit
The dynamic rigidity of the ULSAB structure is remarkably good, as it was already
indicated by the static test results. Windshield and backlight have a significant
impact on the first torsion mode. The difference is in the same range, as known
from other sedan body structures.
The effect on first bending and first front-end lateral mode is relatively small. For
the test configuration with glass, the first torsion mode and the first front-end lateral
mode are coupled at 60.6 Hz.
Chapter 10 - Page 19
Engineering Services, Inc.
Frequency Response Function Amplitude [(m/s2)/N]
Test Unit Modal Analysis with Screens
2
First Bending 62.4 Hz
First Torsion 60.6 Hz
1.8
Bending 63.5 Hz
Corner Points
Front Left
1.6
Front Right
1.4
Rear Left
1.2
Rear Right
1
0.8
0.6
0.4
0.2
0
50
52
54
56
Test Unit Modal Analysis with Screens
Frequency Response Functions, measured at the body corner points
Power input by means of electrodynamic shakers at the body corner points
58
60
62
64
66
68
Frequency [Hz]
Figure 10.4.2-3 Frequency Response Functions - Test Unit
The graph plot above shows the frequency response functions, measured at the
four driving points. Second bending mode at 63.5 Hz occurs mainly in the rear;
whereas the first bending mode occurs in the front and rear of the structure.
Chapter 10 - Page 20
70
Engineering Services, Inc.
The global modes for DH #2 in the described test configuration can be seen in the
following chart:
D H # 2 M o da l A na lys is
First Modes [Hz]
70
66.5
63.9
60
64.9
60.1
57.2
50
47
40
Torsion
Bending
w ithout glass
Front End Lateral
w ith glass
Figure 10.4.2-4 Modal Analysis Results - DH #2
The dynamic rigidity of DH #2 is in the same range as the values of the test unit.
The front-end lateral mode changed remarkably. This is created by the change of
the material gauge of the rail fender support inner from 0.9mm to 1.2mm.
The torsion mode and bending mode without glass decreased slightly, but with
glass, the loss of dynamic rigidity is compensated.
Chapter 10 - Page 21
Engineering Services, Inc.
Frequency Response Function Amplitude [(m/s2)/N]
4
Measurement Points:
First Bending 63.9 Hz
3.8
Body Corner Points
3.6
3.4
Driving Points:
3.2
Body Corner Points
3
2.8
Front Left
2.6
Front Right
2.4
First Torsion 60.1 Hz
Rear Left
2.2
Rear Right
2
1.8
1.6
1.4
1.2
Project:
1
0.8
Test:
0.6
Date:
0.4
Vehicle:
0.2
0
50
52
54
56
58
60
62
64
Frequency
66
ulsabdh2
ULSAB_DH2_mS
18-12-97
ULSAB DH2
Body Structure
with Screens
70
68
Hz
DH #2 Modal Analysis with Screens
Frequency Response Functions, measured at the body corner points
Power input by means of electrodynamic shakers at the body center points
Figure 10.4.2-5 Frequency Response Functions - DH #2
The graph plot above shows the frequency response function, measured at the four
driving points. The amplitude of the first bending increased in relation to the test
unit. This is in correlation with the decrease of the static bending rigidity.
Additional modal analysis was conducted on the ULSAB structure, to investigate the
influence of several bolted and/or bonded parts.
Test configurations:
1.
2.
3.
4.
5.
Full test configuration as described in chapter 10.3.1.1.
As 1, but without bolted brace cowl to shock tower assembly
As 2, but without braces radiator (Part-No.188)
As 3, but without tunnel bridge
As 4, but without radiator support upper (Part-No. 001/094/095)
Chapter 10 - Page 22
Engineering Services, Inc.
Modal Analysis
70
62.4
First Modes [Hz]
60.6
60
62.4
61.0
62.4
61.0
62.3
62.3
60.8
60.3
60.6
53.4
50
47.0
47.3
47.2
2
3
4
40
1
5
Test Configuration
Front End Lateral
Torsion
Bending
Figure 10.4.2-6 Modal Analysis Five Test Configurations
The influence of the bolted brace cowl to shock tower assembly on the front-end
lateral mode of 13.6 Hz is evident.
Test configuration 5 shows an improvement in the front-end lateral mode, but this is
mainly caused by the influence of the mass of assembly radiator support.
The other modifications have no evident impact on dynamic rigidity.
Chapter 10 - Page 23
Engineering Services, Inc.
10.5. Masses in Test Configuration
A crane with a scaled load cell balanced the DH.
Figure 10.5-1 DH #2 on Crane
The measured mass in full test configuration included the mass of the bolted brace
cowl to shock tower assembly and tunnel bridge, which were installed for testing
only (see 10.3.1.1 Test Configurations). The mass of Windshield and backlight
were not included. The mass in this test configuration was the following:
Test Unit
DH #2
197.3 kg
198.5 kg
*This mass includes 2.86 kg for the bolted brace cowl
to shock tower assembly and tunnel bridge
The calculated mass for non-constructed reinforcements and brackets has to be
added (see Chapter 5 on Design and Engineering).
Chapter 10 - Page 24
Engineering Services, Inc.
10.6. Summary
All test results proved excellent performance and coordination between test results
and CAE results for structural performance values.
This is caused by the fact that the approach from former times, to define the
structural body parts by these requirements, is superseded. Nowadays, these body
parts are mainly specified by safety requirements.
ULSAB Testing Results Overview vs. CAE Results
Testing
Test
Testing
CAE
Final
Test
Benchmark
DH #2
Unit
Version
Unit
Average
Targets
Static Rigidity
Torsion
(Nm/deg)
20,800
21,620
20,350
19,020
11,531
≥ 13,000
Bending
(N/mm)
18,100
20,460
20,540
20,410
11,902
≥ 12,200
Modal Analysis
Torsion
(Hz)
60.1
60.6
61.4
61.1
38*
≥ 40
Bending
(Hz)
63.9
62.4
61.8
64.1
38*
≥ 40
Front End Lateral (Hz)
64.9
60.6
60.3
58.5
38*
≥ 40
*1st mode shape varied for each vehicle benchmarked
The results gained by CAE calculations are in good, if not excellent, correlation with
the test results.
Chapter 10 - Page 25
Engineering Services, Inc.
11. Economic Analysis
Engineering Services, Inc.
11. Economic Analysis
11.1. Introduction
The objective of this program was to establish a credible cost estimation of the
ULSAB body structure by using automotive practices of manufacturing engineering,
process engineering and cost estimating.
To undertake this program, Porsche Engineering Services, Inc. (PES) organized an
interactive process between product designers, stamping process engineers,
assembly line designers and cost analysts. The team was comprised of the
following organizations:
Porsche Engineering Services .... Program Management
Knight Engineering .... Stamping Process Engineering
Schaefer GmbH .... Hydroform Process Engineering
Classic Design .... Assembly Process Design
Porsche AG .... Process Validation
Camanoe Assoc. / IBIS Assoc .... Cost Analysis
Because end users would want to analyze “what if” scenarios and compare existing
or potential body structures to ULSAB, the entire program used a technical cost
model program developed by Camanoe Associates (a group of MIT researchers)
and IBIS Associates.
The technical cost model is programmed to allow the user to change any of the
general inputs to suit their specific environment or to change specific inputs for
alternative processes.
In addition, because the costs shown on the ULSAB cost model reflect only factory
costs and are relative to the level of product development as of today, a user may
wish to enter additional cost categories for both ULSAB and a comparative body
structure. The cost model has been arranged to accommodate this.
Chapter 11 - Page 1
Engineering Services, Inc.
Some of the areas not included in the ULSAB Cost Analysis are:
•
•
•
•
•
•
•
•
SQA (Supplier Quality Assurance), quality testing, auditing
Impact on body structure through other system developments, i.e., electrical,
trim, powertrain, etc.
Changes as a result of physical body structure testing
Start up and production launch costs
Marketing campaigns
Transportation costs
Departmental costs, marketing, finance, purchasing, human resources, etc.
Preparation for paint
11.2. The Process of Cost Estimation
11.2.1. Overview
The Economic Analysis of ULSAB began with the establishment of the basic
assumptions regarding general inputs. This was achieved through a series of
meetings between the Economic Analysis Committee of ULSAB and the Economic
Analysis Team.
The program then commenced to establish the estimated production costs against an
extremely well defined design. Having a process design meant that costs could be
analyzed based on exact definitions concerning fabrication and assembly
requirements.
On the parts fabrication side, each stamping and hydroformed component was
studied to determine the process. This step was undertaken by Knight (Stampings)
and Schaefer (Hydroforming) who provided the initial inputs on operation
requirements, equipment requirements, tooling costs, manpower requirements, etc.
On all major components Porsche, Germany confirmed the data.
Chapter 11 - Page 2
Engineering Services, Inc.
Complete Porsche Design
General Inputs - ULSAB
Economic Analysis Committee
Part Definitions
(mass, area, etc........)
Assembly Requirements
(number and type of welds)
Consensus among:
- Camanoe / IBIS
- Knight Engineering
- Porsche Engineering
- Porsche AG
Fabrication Process Parameters
(line run rate, tool cost, press cost,
number of hits)
Assembly Line designed
explicitly for ULSAB
by Classic Engineering
Assembly Process Parameters
(total equipment cost, number of
workers, etc.......)
Cost Model
Cost Model Algorithm
by Camanoe / IBIS
Figure 11.2.1-1 Mechanism for Determination of All Part Inputs
This data was then compared to the mass industry data bank at the Massachusetts
Institute of Technology (MIT) to ensure reasonableness before being used for cost
estimating.
For the assembly line design and processing, PES provided Classic Design with a
detailed bill of materials (BOM) and parts sequencing. From this, each area and
station was developed in a macro view, which established the equipment, tooling,
building and manpower required to fulfill the production requirements. Following
validation by Porsche, Germany this data was then forwarded to Camanoe for final
cost estimation.
Chapter 11 - Page 3
Engineering Services, Inc.
11.2.2. Cost Model Algorithm Development
In this section the methodology for development of the technical cost models is
described. The cost models can be used not only for determining manufacturing
costs for the ULSAB design, but also for costs associated with alternative designs.
The models allow the capability to track the major cost contributors and to
determine opportunities for target areas for reduction.
The principal objective for this project includes development of a cost estimation
tool to aid automotive designers specifically interested in costs associated with the
ULSAB design. The cost model permits any user to easily adapt various input
parameters, allowing cost investigations for alternative designs on a consistent
basis.
The cost model must account for various processes used in the manufacture of the
body structure, including stamping, hydroforming and assembly. Based on
numerous input parameters, both economic and technical, the model tracks cost
contributions to the stamping process from blanking, welding (for tailor welded
blanks) and stamping for all parts. Similarly, hydroformed part costs are broken
down into contributions from bending, pre-forming and the final hydroforming
fabrication. The assembly process costs include cost contributions from spot
welding, active gas metal arc welding (MAG), laser welding and adhesive bonding.
Technical cost modeling is a technique developed and used by Camanoe and IBIS
for simulating manufacturing costs. The technique is an extension of conventional
process modeling, with particular emphasis on capturing the cost implications of
material and process variables and various economic scenarios.
The focus of the technical cost models developed for ULSAB are limited to direct
manufacturing cost, although the models could be expanded to include indirect
costs and aspects of the entire product life-cycle. Direct manufacturing costs
involve specific processes: fabrication and assembly of the body structure. Indirect
manufacturing costs, including executive salaries, marketing and sales, shipping
and purchasing, research and development, and profits are not considered.
Chapter 11 - Page 4
Engineering Services, Inc.
Cost is assigned to each unit operation from a process flow diagram. For each of
these unit operations, total cost is broken down into separately calculated individual
elements.
•
•
Variable cost elements:
Fixed cost elements:
Materials, labor, and energy
Equipment, tooling, building, maintenance,
overhead labor and cost of capital
Developed to breakdown and track contributions from variable and fixed costs, the
models identify the major cost contributors to manufacturing. After the direct
manufacturing costs are established based on an initial set of input parameters,
sensitivity analysis can be performed to indicate the cost impact of changes to key
parameters. Technical cost models provide an understanding not only of current
costs, but also of how these costs might differ in the face of future technological or
economic developments. Typical parameters investigated via sensitivity analyses
include: annual production volume, throughput (cycle time or production rate), raw
material prices and tooling costs.
Models can be implemented in either a descriptive or predictive manner. In either
case, direct inputs are specified for the product material, geometry and
manufacturing scenario. With descriptive models, the user directly inputs the
intermediate parameters such as production rate, equipment cost and tooling cost.
In the predictive approach, the model as a function of the product material and
geometry calculates the intermediate parameters. These predictive functions are
derived from analyzing a continually expanding range of case studies, and are
updated routinely. It is this predictive nature of technical cost models that separates
them from other cost estimating tools.
Chapter 11 - Page 5
Engineering Services, Inc.
11.2.3. General Inputs
As stated previously, the Economic Analysis began with the establishment of the
general inputs. An example of these inputs is as follows:
Input
Production Volume
60 jobs per hour
Working Days per Year
240
Production Location
Mid-West USA
Wage including Benefits
$44.00 per hour
Interest Rate
12%
Equipment Life
20 years
Production Life
5 years
Building Life
25 years
11.2.4. Fabrication Input
For each part in the ULSAB design, a press line time requirement was calculated.
The machine clean running rate, the line downtimes, the part reject rates and the
total annual production volume are used to determine the total time needed on the
line for the given year. This information, combined with the technical requirements
for stamping each part is used to calculate the total number of each press line type
needed to produce the ULSAB body structure. For ULSAB, it was determined that
a total of 15 press lines and five blanking lines were needed to produce all the
necessary parts and blanks.
Chapter 11 - Page 6
Engineering Services, Inc.
1
4500
tons
2
3600
tons
3
4
5
6
7
8
9
10
11
A
B
C
C
C
D
D
D
D
A
B
C
C
C
D
D
D
D
A
B
C
C
C
D
D
D
D
A
B
C
C
C
E
12
E
13
E
14
E
15
A
B3
400 t
400 t
B4
B5
1000 t
B2
600 t
B1
400 t
A
Figure 11.2.4-1 ULSAB Press Shop Layout
The accompanying press shop layout shows the distribution of these 15 press lines
and five blanking lines among the various equipment types shown in the previous
slide. The layout also shows the number of presses required on each line. For
example, there is only one line using “Press Group A” and it contains six presses;
there is one line using “Press Group B” containing four presses; three lines using
“Press Group C” containing four presses each; and four lines using “Press Group D”
containing three presses each. In addition, one of each large transfer press types
and four smaller transfer presses suitable for the progressive die parts were also
used. Finally, one large, one medium and three small blanking lines were required.
Chapter 11 - Page 7
Engineering Services, Inc.
The press line descriptions are as follows:
Press
Capacity
Size
Press Group A:
1600 ton DA/1000 ton SA
4572 mm x 3048 mm
Press Group B:
1000 ton DA/800 ton SA
3048 mm x 2032 mm
Press Group C:
800 ton DA/500 ton SA
2743 mm x 1524 mm
Press Group D:
500 ton DA/350 ton SA
2438 mm x 1220 mm
Press Group E:
350 ton SA
2134 mm x 1220 mm
(Progressive Dies)
Transfer Presses:
4500 ton & 3600 ton
Blanking Lines:
400 ton
2438 mm x 1220 mm
600 ton
2743 mm x 1524 mm
1000 ton
3048 mm x 2032 mm
DA = Double Action
SA = Single Action
11.2.5. Assembly Input
The assembly line was designed explicitly for ULSAB by Classic Engineering which
includes equipment and tooling investment, assembly plant area and labor force.
Cost enhancements concerning material, energy, overhead labor and maintenance
were performed by Camanoe and IBIS.
It is very important to remember that the assembly line was designed for a net line
rate of 60 jobs per hour. Because of the various line downtimes, this requires a
running rate of 72 body structures per hour, which in turn implies that there are only
48 seconds per station to perform assembly operations and transport the body to
the next station. In practice, increasing (or decreasing) the line running rate
changes the time available at each station to perform the assembly operations and
thus changes the line configuration, resulting in different levels of required
investment. Because the line was actually designed for one line speed (net rate of
60 body structures per hour), the model is unable to adjust the investment based on
the different line rates. Consequently, the user MUST change the assembly
investment inputs in order to have an accurate estimate of the assembly cost at
other production volumes. Additionally, ULSAB is costed against specific spot
welds and laser welds, any alteration to this situation would require a re-evaluation
of the equipment and manpower needed.
Chapter 11 - Page 8
Engineering Services, Inc.
11.3. Cost Model Description
The following chapter describes the salient information and input parameters within
the ULSAB Technical Cost Model. With the enormous quantity of input parameters
required for cost calculations, validation and consensus among all participants are
critical for appropriate ULSAB cost determination. A description of the process for
generating consensus on all of the input parameters for the ULSAB design is
discussed.
Information
Machine Rents
Calculations
Part Inputs
General Inputs
Investments
Cost Breakdown
Cost Summary
Overall Costs
Figure 11.3-1 Technical Cost Model Layout
The ULSAB technical cost model consists of the following nine major sections or
sheets, in order of appearance: Overall Costs, Cost Summary, Cost Breakdown,
Investments, General Inputs, Part Inputs, Calculations, Machine Rents and
Information.
Chapter 11 - Page 9
Engineering Services, Inc.
The Overall Costs sheet, appearing first, reports the total cost for body structure
fabrication. This sheet provides the user with a brief synopsis of the model outputs,
which include cost contributors for stamping and assembly of a body structure. As
mentioned in the introduction, the user will be able to input additional costs as
required. The second sheet, Cost Summary, provides more detail by listing cost
contributors for each part ID number or assembly area. The next sheet, Cost
Breakdown, gives further detail on the contributors to part cost. Cost contributors
for each part ID are broken down by process step, and the information in this sheet
is organized slightly differently than in the Cost Summary sheet. No information on
assembly is contained on the Cost Breakdown sheet, only costs related to part
production. The 2 input sheets (General Inputs and Parts Inputs) contain all of the
pertinent input parameters for cost calculation. The Calculations sheet lists
intermediate cost output calculations that may be of interest.
The model includes a sheet that can be used to test the effect of various sets of
input parameters on the machine rents. Finally, the Information sheet gives
information concerning the size and the gages of the blank sizes to be used for
ULSAB.
Organizational Format of Model Sheets
Stamped Parts:
General Output Costs
Process Specific Information
Tubular and Purchased Parts:
General Output Costs
Cost Breakdown by Element
Assembly:
General Output Costs
Cost Breakdown by Element
Figure 11.3-2 Organizational Format of Model Sheets
Chapter 11 - Page 10
Engineering Services, Inc.
Most of the eight sheets are organized in a similar manner, as shown schematically
in the figure above. This organization is consistent for cost sheets and calculation
sheets. By paging down each sheet, three sections become apparent: Stamped
Parts, Tubular and Purchased Parts and Assembly.
By paging across the sheet within each of these sections, the costs for specific
parts or assembly processes (listed by ID) are identified, and sorted into two
categories: General Output Costs and Cost Breakdown by Element.
Within the General Output Costs regions, the total cost for fabricating parts is listed
for each part, identified by part ID and name. Hence part cost information for each
stamped, tubular and purchased part is readily available. The total cost for
fabrication is summed at the bottom of each column and section.
Paging across to the Cost Breakdown by Element region, the total cost for each part
is broken down into nine cost categories, including material, energy, labor,
equipment, tooling, overhead labor, building, maintenance and working capital
costs. Addition of all cost elements in a given row sums to the total part cost. Each
of the nine cost elements is also totaled at the bottom of each column for all parts to
provide a total cost breakout by element in the Stamping, Tubular and Purchased
Parts and Assembly sections.
11.4. ULSAB Cost Results
11.4.1. Overall Cost Results
The cost analysis for the ULSAB design is presented, including a breakdown of
costs by processes, factor elements, and investments. The costs associated with
new technologies are focused upon, specifically for all the tailor welded blank
stamped parts and for the hydroformed side roof rail. Sensitivity analyses are
included for changes in input parameters, which may affect the cost of TWB
processing.
The manufacturing costs for the ULSAB body structure at 203.2 kg with 158 parts
result in an overall value of $947 per body structure.
Chapter 11 - Page 11
Engineering Services, Inc.
The body structure cost can be broken down into $666, from parts fabrication and
$281 from assembly. Of the 158 parts in the ULSAB design, the 94 major stamped
parts make up the majority of the mass (184 kg) and represent the largest cost
element at $584. Tubular parts, such as the two hydroformed side roof rails and the
member pass through beams, as well as a large number of small brackets and
hinges (normally out-sourced by the auto maker), make up only a small portion of
both the overall mass and cost.
Cost
Stamped Parts
Tubular & Purchased Parts
Assembly
Total Body Structure
$584
$82
$281
$947
Number
Mass of
of Parts Parts (kg)
94
64
--158
184.3
18.9
--203.2
Figure 11.4.1-1 ULSAB Overall Cost Results
The breakdown of the variable costs (and the remaining fixed cost total), both for
parts fabrication and assembly, shows the importance of the material and fixed
costs. Material (steel) is the single largest cost driver, accounting for 37% of the
total body structure cost. Total fixed costs (for parts fabrication and assembly
operations), which primarily derive from the investments in plant equipment and
overhead, also lead to 44% of the body structure cost. The labor and energy
contributions are relatively small at a combined total of only 10% for the entire
assembled body structure.
Chapter 11 - Page 12
Engineering Services, Inc.
ULSAB
% of Total
Stamping
Hydroforming
Purchased
Assembly
$584
$41
$41
$281
62%
4%
4%
30%
Total Body Structure Cost
$947
100%
Total Number of Parts
Total Mass
158
203.2 kg
Figure 11.4.1-2 Cost Breakdown by Process Step
ULSAB
% of Total
$353
36
6
189
$584
37%
4%
1%
20%
62%
Assembly
$41
$41
$0
45
10
226
$281
4%
4%
0%
5%
1%
24%
30%
Total Body Structure Cost
$947
100%
Material
Labor
Energy
Fixed Costs
Stamping Parts Fabrication
Hydroforming
Purchased
Material
Labor
Energy
Fixed Costs
Figure 11.4.1-3 Cost Breakdown by Factor
Chapter 11 - Page 13
Engineering Services, Inc.
Investments
ULSAB
(Millions)
% of Total
Blanking Tooling
$4.4
1.4%
$10.1
3.2%
$1.2
0.4%
$37.2
11.9%
Welding Building
$5.9
1.9%
Stamping Tooling
$37.1
11.8%
Stamping Lines
$102.9
32.8%
Stamping Building
$6.1
1.9%
Hydroform Tooling
$1.3
0.4%
$16.3
5.2%
$0.5
0.2%
Assembly Tooling
$19.0
6.0%
Assembly Equipment
$40.4
12.9%
Assembly Building
$31.3
10.0%
$313.7
100%
Blanking Lines
Blanking Building
Welding Line
Hydroform Lines
Hydroform Building
Total Investments
Figure 11.4.1-4 Distribution of Investment Costs
Investments for each process step show that the assembly line and related tooling
and building expenses account for less than one-third of the total. The press shop
is the major source of investment. Press lines account for over 30% of the
investment total. Welding lines for producing tailored blanks are also significant,
despite the fact that there are only 16 tailor welded blank parts used in the body
structure
11.4.2. Cost Breakdown for Fabrication
The parts fabrication total can be further broken down into $584 for major stamped
components (including the Panel Roof which is produced with the Active Hydro-Mec
Process), $41 for the two hydroformed side roof rails and $41 for the remaining
small purchased parts (including ordinary tubes such as the pass-through beams
and a number of small brackets and hinges).
Chapter 11 - Page 14
Engineering Services, Inc.
The primary driver for the major stamped parts is material. Due to the stage of
program development, a very cautious approach was taken in determining blank
sizes; therefore the level of engineered scrap results in a relatively high material
cost.
Cost per
Vehicle
Breakdown for Stamped Parts
Material Cost
Labor Cost
Energy Cost
$353
$36
$6
Total Variable Costs
$395
Equipment Cost
Tooling Cost
Overhead Labor Cost
Building Cost
Maintenance Cost
Working Capital Cost
Total Fixed Costs
TOTAL COST OF STAMPED PARTS
$88
$51
$27
$7
$15
$1
$189
$584
Figure 11.4.2-1 Overall Cost Breakdown for Stamping
As is typically the case, the other main cost components for the stamped parts are
the equipment (press lines) and the tooling.
Chapter 11 - Page 15
Engineering Services, Inc.
11.4.3. Cost Breakdown for Assembly
Body structure assembly contributes less than one-third of the overall body
structure cost. The main cost elements are the labor (mostly the indirect or
overhead labor) and the assembly line equipment. Notable is the relatively low
equipment cost which results from the reduced assembly effort required as a result
of the parts consolidation.
Breakdown for Assembly
Material Cost
Labor Cost
Energy Cost
Cost per
Vehicle
$0
$45
$10
Total Variable Costs
Equipment Cost
Tooling Cost
Overhead Labor Cost
Building Cost
Maintenance Cost
Working Capital Cost
Total Fixed Costs
TOTAL COST OF ASSEMBLY
Figure 11.4.3-1 Overall Cost Breakdown for Assembly
Chapter 11 - Page 16
$55
$50
$23
$125
$18
$9
$1
$226
$281
Engineering Services, Inc.
11.4.4. Cost Analysis for New Technologies and Materials
While there are only 16 parts (eight left/right part pairs) that use tailor welded
blanks, they make up a considerable fraction of the mass of the body structure.
These 16 parts weigh 88.38 kg, which is 45% of the total body structure mass. Not
surprising, they also represent a significant portion of the total body structure cost.
These parts cost $279 to produce, which is 42% of the cost of all parts fabrication.
This, of course, means that these parts cost more per kilogram than the rest of the
body structure. This result is not unexpected because the additional welding step is
required. However, this relatively small cost increase is compensated for by the
reduced part count and thus reduced tooling and assembly costs. Further, the tailor
welded parts offer the mass savings, which is the main objective of the ULSAB
design.
Part #
Material
Cost
Blanking
Cost
Welding
Cost
Stamping
Cost
Total Cost
008/009
$11.96
$0.75
$2.75
$3.97
$19.43
010/011
$18.25
$0.99
$3.02
$4.16
$26.42
042/043
$25.39
$1.07
$2.20
$4.63
$33.29
046/047
$19.08
$1.10
$3.30
$4.94
$28.42
048/049
$9.27
$0.74
$1.95
$4.75
$16.71
060
$39.44
$1.90
$9.53
$11.06
$61.93
061
$39.43
$1.90
$9.53
$11.06
$61.92
070/071
$9.13
$0.49
$4.40
$3.91
$17.93
096/097
$6.78
$0.49
$1.64
$3.61
$12.52
TOTAL
$178.73
64%
$9.43
3%
$38.32
14%
$52.09
19%
$278.57
100%
Figure 11.4.4-1 Tailor Welded Blank Part Cost Breakdown
Chapter 11 - Page 17
Engineering Services, Inc.
The costs of tailor welded parts are still primarily driven by the material costs, which
makes up 63% of the total. This is also true for the body sides (parts 060 & 061)
where the blanking process was especially productionized to decrease the scrap
associated with the large cutouts for the door openings. Processing costs divide
fairly evenly between the welding and stamping operations, with the blanking step
contributing only a small percentage.
$375
Worst of All Inputs
$348
Total Cost of TWB Parts
$350
$325
Min: 50 mm/s
Base: 100 mm/s
Max: 150 mm/s
Max: 40%
Base: 30%
Min: 15%
Max: $5.3 Million
Base: $3.8 Million
Min: $3 Million
$313
$300
$286
$288
Baseline
$279
$275
$268
$272
$274
$260
$250
Best of All Inputs
Weld Speed Downtime
Equipment
Total
Figure 11.4.4-2 Effect of Welding Parameters on TWB Total Costs
A key question regarding the use of a relatively new technology (i.e. tailor welding of
blanks) is the certainty of the process variables and the effect of changes in these
parameters on the part cost. Three major input parameters were considered for this
sensitivity: the weld speed, the line unplanned downtime and the line cost. The
baseline values used in the cost analysis were 100 mm/sec, 30% (four hrs/day
downtime) and $3.8 million respectively. These factors were allowed to vary within
a range of reasonable values. The graph shows that the cost of the parts is most
Chapter 11 - Page 18
Engineering Services, Inc.
sensitive to assumptions regarding the weld speed. A weld speed reduction to only
50 mm/sec would raise the cost by approximately $35. The downtime and line
equipment costs have much smaller effects that might result in increases (or
savings) of less than $10 each. Even under the worst case scenario of low weld
speeds and high downtimes and equipment costs, the total part cost would only rise
by about $50, or about 18%.
Breakdown for One Side Roof Rail
Material Cost
Labor Cost
Energy Cost
Total Variable Costs
Equipment Cost
Tooling Cost
Overhead Labor Cost
Building Cost
Maintenance Cost
Working Capital Cost
Total Fixed Costs
Cost per
Rail
$11.08
1.53
0.11
$12.72
$4.87
0.82
1.23
0.15
0.58
0.05
$7.70
$20.42
TOTAL COST PER RAIL
Figure 11.4.4-3 Cost Breakdown: Hydroformed Side Roof Rail
Hydroforming is the other new parts fabrication technology used in the ULSAB
design. While there are only two hydroformed parts, the left and right side roof
rails, these components enable design changes in numerous other parts in the body
structure. Because this process produces only two parts the cost significance is
relatively low. Each side roof rail is estimated to cost $20, of which the majority of
the non-material related costs result from the hydroforming equipment.
Chapter 11 - Page 19
Engineering Services, Inc.
The draw operation of the panel roof is planned in hydro-mech technology using a
10,000 ton hydraulic press. The investment cost of this press is $84 million,
excluding installation and auxiliary equipment, the resulting operation cost including
material is $18.41. The subsequent operations (trimming and flanging) are done in
conventional presses. As the draw operation needs a far longer cycle time than the
other operations (100 per hour vs. 400 per hour), the production sequencing has
been separated.
Laser welding has been incorporated into four areas of the assembly system. The
total number of laser welders used is 13 at an average cost of $1.2 M each.
High strength steels range in cost from $0.85 kg to $1.16 kg compared to mild steel,
which costs $0.77.
Laminate materials used on the spare tire tub and dash insert is at $3.60 kg. This
results in relatively high prices for these parts.
Chapter 11 - Page 20
Engineering Services, Inc.
11.4.5. Sensitivity Analysis
A key element of the Economic Analysis is to determine the potential cost
movements as a result of sensitivity analysis and other scenarios that could impact
cost.
Areas investigated are labor wage, unit energy costs, equipment life, building unit
cost, production life and material costs:
3 years
5 years
8 years
+ 20%
$44 p/hour
-20%
$1000
$1013
+ 10%
$352
-10%
$994
$982
+ 20%
0.10 $/kWh
-20%
Overall BIW Cost
$975
15 years
20 years
25 years
$955
$950
$950
+ 20%
$1500 p/m2
-20%
$952
$947
$943
$944
$942
$925
$900
$909
$900
$912
$875
Labor
Wage
Unit
Energy
Cost
Equipment
Life
Building
Unit
Cost
Production
Life
Material
Costs
Stamping
Parts
Additionally, Tailored Welded Blanks, Hydroforming and Laser Welding are relatively
new processes. As the utilization of these technologies increases so should
efficiency and this would result in cost reductions.
Chapter 11 - Page 21
Engineering Services, Inc.
11.5. Body Structure – Comparative Study
11.5.1. Overview
Due to the fact that ULSAB’s holistic design approach uses new technologies such
as hydroforming, laser welding, etc., a comparative study using conventional
processes was created in order to analyze the overall competitiveness of ULSAB. A
brief description of the models follows:
•
Year 2000 Reference Model – Base (A)
Year 2000 Reference Model is based upon a generic four door passenger
car body structure. The general body structure definition consists of a
broadly described parts list made of groupings based on their size and
complexity, and grouping of assembly operations based on their level of
automation and size. Costs are generated via existing data, automotive
industry inputs, predictive processes and general assumptions established
by the Economic Analysis Group. The manufacturing processes used in
this study were conventional stampings, spot welding and limited MAG
welding.
•
Year 2000 Reference Model – PES Internal Study (B)
To further analyze ULSAB’s competitiveness, alternative refinements were
made to the Year 2000 Reference Model (A) in order to establish the
potential range of costs for “classical” structures. To establish this,
engineering judgment was used to integrate the general manufacturing
assumptions of the Year 2000 Reference Model (A) with the design
concept of ULSAB. Allowances for additional parts and gage increases
due to the lesser use of high strength steel were made in an effort to
simulate the performance characteristics of ULSAB. The result of this
exercise was Year 2000 Reference Model (B).
As the above described comparative study does not utilize the specific design or
detailed manufacturing cost estimates contained within ULSAB, detail or technical
comparisons with ULSAB cannot be made.
Chapter 11 - Page 22
Engineering Services, Inc.
For the purpose of direct comparisons, a specific detailed cost model of ULSAB in
spreadsheet format is available and will be provided by the ULSAB Consortium to
automotive manufacturers. This will allow the automotive OEMs to directly compare
in detail, their current or future planned models with ULSAB.
Chapter 11 - Page 23
Engineering Services, Inc.
11.5.2. Assumptions
Cost Model Inputs
Year 2000
ULSAB
(A)
(B)*
184
10
9
203
49%
230
0
20
250
55%
248
0
10
258
50%
Direct Labor (Manpower)
Indirect Labor (Manpower)
59
47
79
36
40
28
Total Parts Count
Large Stamped Parts
Medium Stamped Parts
Small Stamped Parts
Hydroformed Rails
Purchased Parts
158
11
39
44
2
62
200
6
79
50
0
65
171
12
54
40
0
65
Total Number of Die Sets
Transfer
Tandem
Progressive
Hydroform
61
14
27
18
2
109
20
59
30
0
65
14
33
18
0
Transfer
Tandem
4.1
3.6
3.8
3.2
4.1
3.6
Hits per Part
Transfer/Tandem Combined
2.5
2.5
2.3
64
178
2,206**
18,286
136
13
114
20,865
80
210
3,250
0
200
0
130
30,000
74
202
3,060
0
154
0
128
28,156
Body Structure Mass
Stampings (kg)
Hydroformings (kg)
Purchased Parts (kg)
Total Mass (kg)
Material Utilization (Stampings)
Parts Fabrication
Hits per Die Set
Assembly
Direct Labor (Manpower)
Indirect Labor (Manpower)
Number of Spot Welds
Length (mm) of Laser Welds
Number of Robots
Number of Laser Welders
Number of Assembly Stations
Assembly Building Area (m²)
* PES Internal study
** Includes 80 spot welds for brackets and reinforcements
Chapter 11 - Page 24
Engineering Services, Inc.
11.5.3. Overall Results
Year 2000
ULSAB
(A)
(B)*
Stamping
$584
$609
$592
Hydroforming
41
0
0
Purchased
41
41
41
Assembly
281
329
308
Total Cost
$947
$979
$941
Total Mass (kg)
203
250
258
* PES Internal Study
Chapter 11 - Page 25
Engineering Services, Inc.
11.6. Conclusion
The ULSAB design is aimed at achieving two significant goals:
•
•
Major mass savings
Improved performance
These goals have been met by implementing appropriate materials and
technologies in to a holistic design approach. Individually some of the processes,
such as, high strength steels, tailored welded blanks, hydroforming and laser
welding are considered expensive, but when used in conjunction with a good design
concept, gage reduction, part consolidation and efficient manufacturing methods, it
results in an extremely cost competitive product.
The results show that the Year 2000 Reference Model iterations are within 3.5% of
the ULSAB cost but carry a major weight penalty.
As this cost difference is smaller than the recognized level of variance generally
considered for a calculated cost estimate, it is accepted that all models would cost
approximately the same.
Therefore, in conclusion, when coupled with good design, the technologies of high
strength steel, tailor welded blanking, hydroforming and laser welding can be used
to achieve mass reduction and performance improvements at no cost penalty.
Chapter 11 - Page 26
Engineering Services, Inc.
12. Summary of Phase 2
Results
Engineering Services, Inc.
12. Summary of Phase 2 Results
The Phase 2 of the ULSAB program has come to its conclusion with the build of the
demonstration hardware.
The test results of the demonstration hardware are remarkable.
Phase 2
Results
Performance
Mass
203
271
- 68
- 25%
Static Torsional Rigidity (Nm/deg)
20800
11531
+ 9269
+ 80%
Static Bending Rigidity
(N/mm)
18100
11902
+6198
+ 52%
(Hz)
60
38
+ 22
+ 58%
First Body Structure Mode
(kg)
Benchmark
Difference
Average
Difference
(%)
Figure 12-1 Structural Performance Summary
Relative to the benchmark average vehicle mass of 271 kg, the mass reduction
achieved is 68 kg (25%).
The static torsional rigidity exceeds the target. The efficiency (rigidity / mass) has
increased, in relation to Phase 1, to 102.5 [(Nm/deg)/kg] (Fig. 12-2). The Phase 2
structural performance results are shown in the graphs as a tolerance field rather
than a fixed point. To indicate that the mass and the performances can vary from
one demonstration hardware structures to another, as it would also do in real mass
production. The static bending rigidity as well as the first body structure mode have
also been increased in comparison to the Phase 1 results (Fig. 12-3 and 12-4).
These high levels of static and dynamic rigidity provide an excellent basis for a
complete vehicle development in respect to its NVH behavior.
Chapter 12 - Page 1
Engineering Services, Inc.
Torsional Rigidity vs. Mass
110
24
Cb (x1000) [Nm/deg]
Ct/m
60
18
14
80
ULSAB
Phase I
20
16
90
70
22
20.8
100
ULSAB
Phase II
50
Future
Performance
Reference
ULSAB
Target
40
12
30
Current
Average
10
8
20
6
4
180
200
203
220
240
260
280
300
320
340
m [kg]
All data adjusted to target vehicle
Cb with Glass, m without Glass
Reference Vehicles: Acura Legend, BMW 5 series, Chevrolet Lumina, Ford Taurus, Honda Accord, Lexus LS 400,
Mazda 929, Mercedes Benz 190 E, Toyota Cressida
Figure. 12-2 ULSAB Phase 2 Torsional Efficiency
Bending Rigidity vs. Mass
110
100
90
80
Cb/m
70
24
22
ULSAB
Phase II
60
20
Cb (x1000) [N/mm]
18.1 18
50
16
14
Future
Performance
Reference
ULSAB
Phase I
ULSAB
Target
40
12
30
Current
Average
10
8
20
6
4
180
200
220
203
240
260
280
300
320
340
m [kg]
All data adjusted to target vehicle
Cb with Glass, m without Glass
Reference Vehicles: Acura Legend, BMW 5 series, Chevrolet Lumina, Ford Taurus, Honda Accord, Lexus LS 400,
Mazda 929, Mercedes Benz 190 E, Toyota Cressida
Figure. 12-3 ULSAB Phase 2 Bending Efficiency
Chapter 12 - Page 2
Engineering Services, Inc.
First Body Structure Frequency vs. Mass
70
65
ULSAB
Phase II
60.1 60
ULSAB
Phase I
55
Future
Performance
Reference
f [Hz]
50
45
ULSAB
Target
40
35
Current
Average
30
25
20
180
200
203
220
240
260
280
300
320
340
m [kg]
Lowest global frequency
f with Glass, m without Glass
Reference Vehicles: Acura Legend, Chevrolet Lumina, Ford Taurus, Honda Accord, Lexus LS 400,
Mazda 929, Toyota Cressida
Figure. 12-4 ULSAB Phase 2 Frequency Efficiency
The results of the crash analysis confirmed the integrity and safety of the ULSAB
structure. The AMS Offset Crash is considered one of the most severe crash tests
of today. In recently performed comparison crash tests of AMS, with the same
vehicle towards a deformable barrier with 40% offset at 64 km/h versus the AMS
Offset Crash barrier with 50% offset at 55 km/n, the results were nearly equal. This
confirms that the decision to analyze the ULSAB structure for its offset crash
behavior using the AMS test configuration, determined at the beginning of Phase 2
in 1995, was the right choice.
The NCAP 100% Frontal Crash was run at 35 mph, 5 mph above the federal
requirement of FMVSS 208, meaning 36% more energy had to be absorbed.
In both the 50% Offset and 100% Front Crash low footwell intrusion and structural
integrity proved the safety of the structure.
Chapter 12 - Page 3
Engineering Services, Inc.
The rear impact crash analysis, also run at 5 mph above the required speed of
30mph and showed fuel system integrity, passenger compartment integrity, residual
volume and door opening after the analysis.
The side impact crash analysis showed good results for criteria, such as passenger
compartment intrusion, B-Pillar displacements and overall shape of deformation.
The roof crash analysis proves that the roof meets the federal standard
requirements and is stable and predictable.
The crash analysis was run with a vehicle crash mass of 1612 kg, meaning
secondary weight savings of other components such as engine; suspension, etc.
were not considered, to achieve a conservative approach.
Apart from the design of the structure and its optimized smooth load flow from front
and rear rails into the rocker and the side roof rail concept; the use of high strength
steels in 90% relative to the ULSAB structure mass was the key to achieve this
crash performances at low mass.
This need to use high strength steel to achieve this crash performance with the
given target for mass was a challenge for the part design and our suppliers.
Together with steel suppliers, part manufacturers, designers and engineers, the
right materials were selected and the design was modified until it was feasible.
Significant mass reduction was also achieved with the use of tailor welded blanks in
combination with high strength steel. The elimination of reinforcements and joints
between parts reduced mass and enhanced crash and structural performance.
Furthermore, the total number of parts and assembly steps was reduced. With the
use of the tubular hydroforming manufacturing process for the side roof rail and
sheet metal hydroforming for the roof panel, parts could be manufactured,
contributing to performance and weight reduction. The hydroformed side roof rail
made from a tube with a relatively large diameter of 96mm and a wall thickness of
1mm from high strength steel was made feasible in Phase 2.
Chapter 12 - Page 4
Engineering Services, Inc.
The assembly sequence of the ULSAB structure with the body side inner
subassembly, first assembled to the underbody structure and the body side outer in
the following step, gives better weld access, especially in the rear of the structure.
With this assembly sequence, weld access holes can be avoided and structural
performance can be maintained.
Laser welding in assembly is successfully applied to weld the body side outer panel
and the roof to the side roof rail. In addition, it was used to join the fender support
rails and the front rails to enhance the performance.
In terms of the cost analysis, following extensive work in detail processing of
components and assemblies, it was established that ULSAB would cost $947 to
manufacture. The competitiveness of this cost is due to the design concept, which
consolidated parts and eliminated many reinforcements, therefore saving stamping
and welding operations.
These savings were partially offset by the cost of high strength steel and the new
technologies such as laser welding and hydroforming, but the final conclusion of the
analysis is that ULSAB can be produced without cost penalty.
Chapter 12 - Page 5