Predicting distortion in vehicle body
assemblies
Iain Masters & Xinmin Fan
EuroPAM
5th October 2005
© 2004 IARC
Outline
PARD Programme
Background
Causes of Deformation
Software Requirements
Initial results with Steel assemblies
Future work
© 2005 IARC
EuroPAM – 5th October 2005
2
PARD Programme
 Collaboration between Advantage West
Midlands, Jaguar Land Rover, Warwick
Manufacturing Group and the automotive
supplier base
 Objective is to improve competitiveness of
OEM’s and their suppliers, through
partnership in the programme, to develop
leading edge technologies and best practices
© 2005 IARC
EuroPAM – 5th October 2005
3
Background
Dimensional Variation in body assemblies associated
with: Component variation

DVA type software
assumes rigid parts
 Fixture / Jig

Wear addressed by regular
maintenance
 Joining method

Mechanical, thermal
distortions not
addressed
© 2005 IARC
EuroPAM – 5th October 2005
4
Need for Simulation tool
 More accurate control of BiW assembly variation
 Optimising manufacturing cycle times and quality
 Reduced jig/fixture development time
 Introduction of ‘new’ materials
 Aid to decision making
© 2005 IARC
EuroPAM – 5th October 2005
5
Joining Methods
 Resistance Spot Weld
(RSW)
 Self Piercing Rivet
© 2005 IARC
EuroPAM – 5th October 2005
6
Observed Distortions with RSW and
SPR in Al Top-Hat Assemblies
Aluminium Top-hat / Top-hat assemblies showing deformation
caused by Resistance Spot Welding and Self Pierce Riveting
© 2005 IARC
EuroPAM – 5th October 2005
7
Observed Distortions with RSW and
SPR in Top-Hat Assemblies
3.0
Displacement (mm)
SPR
2.5
2.0
RSW
1.5
RSW
1.0
0.5
SPR
0
2 mm gauge
1.5 mm gauge
Aluminium
Mild steel
Maximum distortion across the flanges of two top hats
joined flange to flange
© 2005 IARC
EuroPAM – 5th October 2005
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Resistance Spot Welding
 Distortion around
RSW caused by sheet
separation
Sheet separation
5mm
 Sheet separation
arises from expansion
and contraction in the
fusion zone
Electrode
penetration
Nugget
penetration
HAZ dia.
Nugget dia.
© 2005 IARC
EuroPAM – 5th October 2005
9
New Automotive materials
 Reduce environmental impact of vehicles
 Issues for RSW Joining


High Strength Low Alloy steels
•
higher energy input than conventional steels
•
short hold time to avoid quenching
Aluminium
•
High welding currents
•
High electrode forces
•
Short weld times
© 2005 IARC
EuroPAM – 5th October 2005
10
Software requirements
 Ability to model local distortions around a spot
weld

Electro / Thermal / Mechanical interactions
 Modelling of assembly process

Welding sequence

Clamping conditions
© 2005 IARC
EuroPAM – 5th October 2005
11
Local - Global Modelling Technique
LO
2d model of individual weld
CA
L
3d model of individual weld
M
OD
EL
Application of 1st weld
Application of final weld
GL
OB
AL
M
OD
EL
Release from fixture
© 2005 IARC
EuroPAM – 5th October 2005
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Validation of Local Weld Model
(a) Nugget size
(b) Sheet separation
(Welding current=10.5 KA, Electrode force = 2.5 KN, Welding time = 15 cycles)
Nugget size and Sheet separation
© 2005 IARC
EuroPAM – 5th October 2005
13
Validation of local weld model
Target
Actual
Simulation
>4.9
6.0
6.1
Nugget penetration (mm)
-
1.1
1.3
HAZ dia. (mm)
-
7.2
7.6
Sheet separation 5mm
from centre (mm)
<0.15
0.1
0.12
Electrode penetration
(mm)
<0.15
0.006
0.16
Nugget dia. (mm)
© 2005 IARC
EuroPAM – 5th October 2005
14
Distortion Prediction – Effect of Weld
Sequence
(a) Inline joining sequence
z
Weld sequence path
x
11
10
9
8
7
6
5
4
3
2
1
z
x
y
y
(b) Spiral joining sequence
z
Weld sequence path
y
x
12
13
14
15
16
17
18
19
20
21
22
21
17
13
9
5
1
4
8
z
12
16
x
20
y
22
18
14
10
6
2
3
7
11
15
19
Steel Top-hat / Flat plate assembly
© 2005 IARC
EuroPAM – 5th October 2005
15
Physical Validation
Welding Top Hat assembly
CMM measurement of assembly
© 2005 IARC
EuroPAM – 5th October 2005
16
Comparison of Test and Simulation
0.171
-0.389
-0.259
CMM measurement
© 2005 IARC
-0.18
0.187
Simulation result
DC01 + Zintec Top-hat / Top-hat assembly – in-line welding sequence
EuroPAM – 5th October 2005
17
Comparison of Test and Simulation
STEEL TOP-HAT / TOP-HAT INLINE WELDING SECTION 1
0.5
0.4
CLAMP - Meas
Displacement (mm)
0.3
0.2
0.1
CLAMP - Meas
UNCLAMP - Meas
0
0
50
100
150
200
250
-0.1
300
350
UNCLAMP - Meas
-0.2
-0.3
-0.4
-0.5
Distance from Left end of test piece(mm)
© 2005 IARC
EuroPAM – 5th October 2005
18
Comparison of Test and Simulation
STEEL TOP-HAT / TOP_HAT INLINE WELDING SECTION 5
0.5
0.4
0.3
Displacement(mm)
CLAMPED - Meas
0.2
0.1
UNCLAMPED - Sim
0
CLAMPED - Sim
0
50
100
150
200
250
300
350
-0.1
-0.2
-0.3
-0.4
UNCLAMPED - Meas
-0.5
Distance from Left end of test piece(mm)
© 2005 IARC
EuroPAM – 5th October 2005
19
Comparison of Test and Simulation
STEEL TOP-HAT / TOP-HAT INLINE WELDING SECTION 7
0.5
CLAMPED - Meas
0.4
Displacemnet (mm)
0.3
0.2
0.1
UNCLAMPED - Sim
0
-0.1
0
UNCLAMPED - Meas
50
100
150
200
250
CLAMPED - Sim
300
350
-0.2
-0.3
-0.4
-0.5
Distance from Left end of test piece(mm)
© 2005 IARC
EuroPAM – 5th October 2005
20
Conclusions
 Successful prediction of direction of deformation
 Underestimate of magnitude of distortion

Component & Fixture accuracy?

Mesh size?
 Projection of welds on to global model and model
size could be extremely large
 Extensive material data is required
© 2005 IARC
EuroPAM – 5th October 2005
21
Future Work
 Case study with actual part
 Validate model for RSW of aluminium
 Use Pam Stamp Simulations as the starting point
to incorporate distortion and residual stress
information into SYSWELD
© 2005 IARC
EuroPAM – 5th October 2005
22
Acknowledgements
© 2005 IARC
EuroPAM – 5th October 2005
23
Predicting distortion in vehicle body
assemblies
Iain Masters & Xinmin Fan
Warwick manufacturing Group
International Automotive Research Centre
The University of Warwick
Coventry
CV4 7AL
UNITED KINGDOM
+44 (0)24 7657 5380/5408
© 2004 IARC