Generation of Optimised Hybrid Electric Vehicle Body in White Architecture from a Styling Envelope
O. Grimes*, A. Appella*, C. Bastien*, J. ChristensenEHTC 2013 - Turin* Coventry University, Department of Engineering and Computing, Priory Street, Coventry, CV1 5FB
1. Previous Work & Research2. Vehicle Design Volume Definition3. BIW Load Path Identification4. BIW Member Sizing5. BIW Member Shape and Gauge6. Automation of the Process7. Conclusion
Audi A6Mazda CX5Typical Body in White (BIW) architectures have evolved over many years toachieve legal and consumer safety test performance, but the underlyingarchitecture has remained very much the same.Is this now the most efficient architecturelooking forward to electric vehicles (EV’s)??
Inertia Relief was demonstrated a reasonable methodof applying inertial crash loading during topologyoptimisation to extract ideal structural load paths. Thispresented the opportunity to develop a method ofproposing new vehicle architectures.*(Towards the Lightweighting of Low Carbon Vehicle Architectures using Topology Optimisation, 2012) IRaddk 0F k u u0 k F k u
Finds optimal material distributionthroughout a design volumeImprovements:• Separated Door (Rigid Hinges)• Windows• Removal Non-Design Areas• Allocation of AUX Components• IR Stability (Compliance Control)Limitations:• Solid beam members• No beam Sizing or Shape• No buckling consideration• Final mass still > 2 tonnes• Unfeasible manufacture
Inclusion of all AuxiliaryComponents• All components of significantmass included.• Rigid elements to centre ofmass locations.• Rigid elements attached to non-design elements.• Additional masses for largecomponents at mounting points.• Rigid suspension modelled withdamper and lower arm points.
• First Order Tetrahedral Elements• Use of Optimisation Controls– DISCRETE– MINDIM• Inertial Relief• Concentrated Point Masses• Nodal Displacement Responses2 – 3mm• Volume Reduction Objective25mmMesh15mmMesh
Using the wireframe meshed with beamelements• Tube profile chosen• Outer diameter and thickness (DEQATN)• Shear Panels• Per member/Per element• Symmetrical properties• Displacement constraints (10mm-20mm)• Loads applied directly to beam elements• Buckling ConsiderationPer BeamMemberMethodPer Element Method
Buckling Equations• Euler Equation• Applied in critical areas• Response to max elementforce within a member• Only considers static bucklingOD = 60 mmOD = 51 mm𝐵 𝐿𝑜𝑐𝑎𝑙 𝐹𝑎𝑐𝑡 =64𝐹 𝑚𝑎𝑥 𝐿𝐸𝜋3(𝐷 𝑜4− 𝐷𝑖4)
OptiStruct provided all round bestoptimisation package:• Fully integrated into HyperMeshand FE solver.• Considerably Lower Run Times• Converged solution, every time• Instant post processing using.prop import• Variable sizing through membersStarting from 35mm RadiusStarting from 70mm Radius
Full Shape MorphingCross Section MorphingFinal Mass: 0.118kgFinal Mass: 0.112kg
Requirements:•Discrete Design Variable•Function: Sum of Thickness•Function Constraint•DependenciesReinforcement Selection ResultsLocal Morphing Ability
Reinforcement Integration to Shape Selection ResultsFinal BeamDesignOptimisation Example Set Up:•Objective: Minimise Mass•Constraints: Displacement (4mm)Reinforcements•Design Variable: Morphing Shapes
•Vehicle must be able towithstand Loads on bothsides.•Applying Loads to bothsides increases LoadCases.•Increased Load CasesIncreases responsenumbers increasing solvertime.•Implementing Symmetryplane causes both sides tobe optimised for themaximum force.
InitialMorphingBeamDiameter• Average diameter taken of allbeam elements within 1D member.• Diameter applied to 2D beamdiameter.• Shape variation becomes afunction of 1D beam optimisation.• Initial diameter should be closed tooptimised diameter.
• Design Volume from Styling– Removal of Aux Comps– Removal of Cabin Volume• Topology Stage– CONM’s for Aux Comps– Combine Opti Controls– Separation of Apertures• Wireframe– Shrink Wrap Topology– User Interpretation/No Auto• Beam Model– Per member/Per Element Opt• Morphing– With Initial Sizing– Map Morph to Wireframe– For each Beam– Replace ForcesLABOUR INTENSIVE,NEEDS AUTOMATION!!
The optimisation process and accompanying scripts present a method ofexamining varying vehicle architectures and extracting realistic BIW sectionsin less than a day. Enabling fast design and effect studies.
Thank you for your attention....any questions?