Low Carbon Vehicle Technology Project
(LCVTP)
WS 7 Lightweight Structures - Technology Review
November 17th 2011
Geraint
Williams
WMG
Low Carbon Vehicle Technology
Workstream 7.6: Lightweight Vehicle
Structures.
Dissemination Event 17th
November 2011
Christophe Bastien
Jesper Christensen
Richard Nicholson
Content
 Low Carbon Vehicle Technology Project (LCVTP) Deliverables
 LCVTP Work Packages
 BIW Holistic Optimisation
 Limitations of Topology Optimisation
 Generation of front-end Crash Structure
 Battery casing proposal
 Vehicle Packaging Study
 Vehicle Dynamics Study
 Conclusions
 Next Steps
 Outputs
LCVTP Deliverables





Range Extended Electric Vehicle (REEV) architecture
Lightest structure possible (~200kg)
EuroNCAP compliant
Best in class for torsional rigidity
Affordable for high volumes (>100,000)
> Steel baseline is assumed
 Based on Tata Beacon vehicle concept
 Scalability for JLR vehicles
Presented Study
 18 months of research connected with the Low Carbon Vehicle
Technology Project (LCVTP)
 Design Process used to firstly obtain a first draft for this BIW,
utilising topology optimisation, by means of HyperWorks.
 Process includes:
> Drivetrain and general packaging requirements associated with a Hybrid Electric
Vehicle (HEV).
> Includes aspects such as sensitivity analysis (of the results obtained)
> in addition to HEV roof topology, including potential effects of the recently
proposed changes to the Federal Motor Vehicle Safety Standard (FMVSS) 216.
BIW Holistic Optimisation
Loadcases Considered
 Average element size: 25mm.
 103000 nodes
 527000 elements.
 Material: Steel (MAT1) - linear elastic
LoCked Elements Densities
 Elements near load
disappeared (instability)
 Solution: large loads when
connected to non-design
elements (helped a lot) 70
Initial Results
 Used beam sizing to evaluate
section areas and BIW mass (208 kg)
 On target for mass
 Increase detail within optimisation
process
Floor Topology (SPC)
 Battery: 200kg
 Range extender: 110kg
 Effect of topology
 Floor topology when using SPCs
Floor Topology (IR)
 Floor topology with SPC do
not make sense (IR
investigated)
 IR balances external loading
with inertial loads and
accelerations within the
structure itself.
 “Addition" of an extra
displacement-dependent load
to the load vector [kadd]
{
{
}
F
[
}

F k u
=
=
{
[
k
}


{
[
u
}

k

0
u
=
/~
[

{

0
• HPC Solver: 2 core
k add
 SPC: 16.5 hours (stiffness
matrix needs reforming
each time the BC are
altered)
 IR: 1.4 hours (straight
solving)
}
Comparison of Floor
Topologies
•SPC
•IR
Sensitivity Study
 Impact angle variation was then
considered in the topology
optimisation
No major changes
on the topology
results
 Battery Stiffness was considered
Investigation on
FMVSS216 (Roof crush)
 Investigation of the potential
effects of the recently
proposed changes to the
Federal Motor Vehicle Safety
Standard (FMVSS) 216 upon
the BIW topology.
 Big changes
 General layout:
Mass Optimised BIW
Limitations of Topology
Optimisation
Limitation of linear
topology optimisation
 SPC are not possible to use
for ideal component location.
 IR can be used.
 “Full” inertial / dynamic
effects not possible to
include
 LCED “restraints” the
 Buckling modes not
optimisation
captured (e.g. longitudinals)
 Optimisation model stability
 Bifurcation problems
 Widespread “triangulation”
 Interpretation of results:
> Passenger cell
> Crash structure
Generation of front-end CRASH
structure
Front
FrontCrash
CrashStructure
Structure
Front Crash Structure
 'g' max: 32.9 'g'
 /ntrusion: 526 mm
 Mass: 40.9 kg
Front Crash
CrashStructure
Structure
 Coupling crash simulations with HyperMorph and HyperStudy
to investigate the influence of shape and thickness modification
 Optimization was focused on entire structure and individually
on the upper transverse beam
 HyperMorph enabled defining complex shape modifications (variables)
 DOE runs generated and evaluated using HyperStudy (HyperOpt engine
applied to find the optimum set of parameters)
Reduced thickness of the sheet metal components and redesigned
upper transverse beam
Front Crash Structure
 Mass reduction:
3.154 kg (-7.7 %)
 Max displacement increased
from 526 mm to 539 mm
Max acceleration increased
from 32.8 ’g’ to 37.4 ’g’
 Crash pulse characteristic
remained
Battery casing PROPOSAL
Battery Casing Design
• Battery load: 30’g’
Vehicle Package Study
Vehicle Packaging Study
 Compare packing constraints of ICE and EV components.
 Consider mass distribution and topology results.
 Consider front end crash structure conclusions.
 Suggest and discuss thoughts on how new EV components can
be packaged.
 For Beacon vehicle
 ForFreelanderEV
Vehicle Packaging Study
 Electric Motor
 Where can they be positioned
 What impact do they have on structure
 Batteries
 Environmental conditions
 Security and Maintenance
 Small Car vs 4x4 how the different vehicle uses change the
configuration.
Vehicle Dynamics Study
Vehicle Dynamics Initial Analysis
 A basic study on the impact of key changes to the vehicle
architecture was undertaken by moving key components
(batteries, APU and inverter pack) through different
configurations
 The aim was to understand the overall impact and
performance of the vehicle’s lateral response
characteristics (i.e. “understeer / oversteer” of a form)
 From work through the optimisation, the key locations
were identified for the components
Vehicle Dynamics Study
 This work was carried out through a supervised MSc project
at Coventry University
 It was found that configuration six provided the best overall
characteristics for the vehicle response inline with other
outputs
 This is only an initial study with a number of assumptions but
provides an initial benchmark for the vehicle configurations
LCVTP Conclusions
 A holistic method has been derived to engineer a HEV
lightweight structure using HyperWorks
 Use of LCED and IR are necessary
 Results make sense for the ‘safety cell’
 Still some limitations on areas subjected to buckling
where a bifurcation event cannot be calculated
accurately with an implicit solver (explicit is needed)
LCVTP Next steps
 Re-develop a beam model of final proposal to validate
BIW mass and check for buckling integrity and
displacements of ‘safety cell’
 Perform detailed CAD data and base initially section
properties on beam section study
 Validate safety deliverables based on shell FEA model
 Work with a high detail of component data and next
generation BIW optimisation to produce more specific
vehicle package and vehicle dynamics studies
LCVTP Next steps
 A proposed paper on the results of this work will be
generated
 Follow on work through student projects is being
conducted:
1.
An BEng project on the effect of occupant impact on vehicle responses i.e.
is there one or six passengers
1.
MEng project on front/rear suspension optimisation
LCVTP Outputs
 An HTML document which details all aspects of WS7.6
> A holistic method derived to engineer a HEV
lightweight structure.
> Reports relating to:
 Vehicle Packaging
 Front End Crash
 Battery Box
 Explicit Modelling using a Linear modelling software
> All published papers for conferences.
Acknowledgements
• The authors would like to thank:
> Mr. Mike Dickison, (of Coventry University),
> MIRA Ltd.
> Tata Motors European Technical Centre (TMETC)
> Jaguar Land Rover (JLR)
> Warwick Manufacturing Group (WMG)
> Advantage West Midlands (AWM)
> and other contributors to the Low Carbon Vehicle Technology Project
(LCVTP) for supplying data and guidance to assist in the making of this
presentation.