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Towards the Lightweighting of Low Carbon Vehicle Architectures using Topology Optimisation
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Transcript of Towards the Lightweighting of Low Carbon Vehicle Architectures using Topology Optimisation
C. Bastien*, J. Christensen*, M. Blundell *,
M. Stefuca**, N. Ravenhall***, A. Garewal***
Towards the Lightweighting of
Low Carbon Vehicle Architectures
using Topology Optimisation
EHTC 2011 - Bonn
* Coventry University, Department of Engineering and Computing, Priory Street, Coventry, CV1 5FB
** Altair Engineering Ltd., Imperial House, Holly Walk, Royal Leamington Spa,CV32 4JG
*** Jaguar Cars Ltd., Engineering Centre, Abbey Road, Coventry, CV3 4LF
Content
• Low Carbon Vehicle Technology Project (LCVTP)
Deliverables
• LCVTP Work Packages
• BIW Holistic Optimisation
– Locked Elements Density (LCED)
– Boundaries vs. Inertia Relief
• Limitations of Topology Optimisation
• Generation of front-end Crash Structure
• Floor Design Proposal
LCVTP Deliverables
• Project £19million
• Sponsor: Advantage West Midlands
• Hybrid HEV 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
LCVTP Work Packages
Work
Package Description Leader 1 Batteries Tata
2 Drive Motors Zytek
3 Power Electronics Warwick University
4 High Voltage Electrical Distribution Systems Tata
5 Auxiliary Power Units Ricardo
6 Vehicle Supervisory Control Ricardo
7 Lightweight Structures Coventry University
8 Vehicle Dynamics Jaguar/ LandRover
9 HVAC and System Cooling Coventry University
10 Parasitic Losses Ricardo
11 Energy Recovery and Storage Ricardo
12 Aerodynamic Performance Coventry University
13 HMI Warwick University
14 JLR Validation Vehicle Jaguar/ LandRover
15 Tata Validation Vehicle Tata
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 Altair
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
# Load case Applied force Applied force magnitude,
EVM = 1200 kg
1 Front impact(ODB) 60 * g * EVM 707 kN
2 Pole impact 300 kN 300 kN
3 Side barrier impact 300 kN 300 kN
4 Roof crush (A-pillar) 2.5 * g * EVM 29.5 kN
5 Low speed rear impact 150 kN 150 kN
6 High speed rear impact 60 * g * EVM 707 kN
7 Torsion Unit
• Average element size: 25mm.
• 103000 nodes
• 527000 elements.
• Material: Steel (MAT1) - linear
elastic isotropic.
LoCked Elements Densities
• Elements near load
disappeared (instability)
• Solution: large loads
when connected to non-
design elements (helped
a lot) 70 iterations
• Keep areas as small as
possible in order to
maximise computation on
design volume (loads and
SPCs)
Initial Results
• Used beam sizing to
evaluate section
areas and BIW mass
(208kg)
• 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 shape topology
output independent of
battery permutations !
Not logical…
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]
• HPC Solver: 2 core
• SPC: 16.5 hours
(stiffness matrix needs
reforming each time the
BC are altered)
• IR: 1.4 hours (straight
solving)
F k u
IR
add
k 0F k u u
0 k
Comparison of Floor
Topologies
• SPC • IR
Batteries
Same void
regardless of
battery
permutations
IR result
more
logical
Sensitivity Study
• Impact angle variation
was then considered
in the topology
optimisation
• Battery Stiffness was
considered
No major changes
on the topology
results
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:
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.
• LCED “restraints” the
optimisation
• Optimisation model
stability
• Widespread
“triangulation”
• .
• “Full” inertial / dynamic
effects not possible to
include
• Buckling modes not
captured (e.g.
longitudinals)
• Bifurcation problems
• Interpretation of results:
– Passenger cell
– Crash structure
GENERATION OF FRONT-END
CRASH STRUCTURE
Front Crash Structure
Longitudinal beams + crush cans (1), bumper
beam (2), short longitudinal beams (3),
transverse beam (4)
2 1
4
3
Front Crash Structure
• ‘g’ max: 32.9 ‘g’
• Intrusion: 526 mm
• Mass: 40.9 kg
Front Crash 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
• Weight 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
FLOOR DESIGN / BATTERY
CASING PROPOSAL
Battery Casing Design
• Battery load: 30’g’
Floor Proposal
• Recommended battery
position for LCVTP
minimum BIW mass
(under driver seat)
• Battery encased in cradle
secured in horse-shoe
hybrid floor (honeycomb
and metal)
LCVTP Conclusions
• A holistic method has been derived to engineer
a HEV lightweight structure using Altair
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
Acknowledgements
• The authors would like to thank:
– Mr. Mike Dickison, Mr. Richard Nicholson (both of Coventry
University),
– Mr. Alistair Crooks of MIRA Ltd.
– Tata Motors European Technical Centre (TMETC)
– Jaguar Land Rover (JLR)
– Warwick Manufacturing Group (WMG)
– Advantage West Midlands (AWM)
– the European Regional Development Fund (ERDF)
– and other contributors to the Low Carbon Vehicle Technology
Project (LCVTP) for supplying data and guidance to assist in the
making of this presentation.
Thank you for your attention.
...any questions?