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  1. 1. OPTIMIZED DESIGN OF VEHICLEUNDERBODY SYSTEMEATC 2013 - TurinEmanuele SantiniProducts and Systems Simulation SpecialistProduct Acoustic and Thermal PerformanceAutoneum Management AG, CH-8406 Winterthuremanuele.santini@autoneum.com . www.autoneum.com
  2. 2. AGENDA2EATC - E. Santini - 23/04/20131. Introduction – Autoneum2. Problem definition3. Analysis – Design Guidelines CAE based4. Test case 1 – Design Optimization (Guidelines VSOptistruct)5. Test case 2 – Design Optimization = f(packaging space)6. Test case 3 – Stress reduction possibilities7. Conclusion
  3. 3. 3Leading partner for the major light vehicle and heavy truck manufacturers around theworld. Unique combination of core competences: Leading acoustics and thermal management Product excellence Global presence with a broad customer portfolioInnovative and cost effective solutions for noise reduction and thermal managementto increase vehicle confort valueFocus on underbody as exterior acoustic and structural parts; fiber consolidatedparts (glass fiber free).Introduction – Who is Autoneum?EATC - E. Santini - 23/04/2013
  4. 4. Problem Definition4Optimise the design of underbody panels, in order to fulfil OEMs structural requirements with the minimalmaterial / part layout, in a very short timeline.Define general design guidelinestaking into account:- Aerodynamic load- Standstill deflection- Water absorption- Free-Free flexural behaviour- Number of fixation points- Stone chipsEATC - E. Santini - 23/04/2013AA
  5. 5. CAE Pre-Development/DevelopmentUnderbody Design Process5Underbody SystemFinal CAD design model Optimize beadings design Maximize part stiffness Reduce part weight Optimize material layout,tailored thickness distribution Aerodynamics pressuredistribution Thermal characterizationand temperature distribution CFD lift and dragMechanical SimulationAero-Thermal SimulationEATC - E. Santini - 23/04/2013
  6. 6. Preliminary Analysis6Deflection reduced of 37%Deformation shape totally changedFixation points influence Not all design modifications bring real benefits to thestiffness of the panel, depending on the configurationof the fixation points, and on the load caseconsidered.Design modifications: Exploiting the stiffness coming from thefixation points Connecting the weakest areas of the part,changing the shape deformationDeformation reduction of 12.5% with 1 beadMax deformation increased of 20% with 1 beadand 25% with 3EATC - E. Santini - 23/04/2013Load case Influence
  7. 7. 7Analysis- Optistruct Topography Optimization -Optimized distribution of shape reinforcements in a design region,taking into account:- Geometry and fixation points of the panel- Loading case (aerodynamic load, snow load, modes…)Optimization Targets:- Increase the stiffness under a specific load case- Maximize the resonant frequencies- Decrease the strains/stresses at the fixation pointsDesign Variables:- Beads height- Beads width- Draw angle- Minimum distance particular pattern constraints can be imposedConstraints:- Packaging space available- Minimize the weight- Beads dimensions (width)- A minimum target for another load caseEATC - E. Santini - 23/04/2013
  8. 8. 8EATC - E. Santini - 23/04/2013• Identification of the most important parameters• Optimization applied on panels with variable parameters• Best beading design for different possible configuration Right design modifications can be applied W/O the mean of the optimizationBoundary Conditions (features) Variables NbDistance between fixation points 10Offset between the plan of the fixationpoints and the part’s plan4Design Variables (beading design) Variables NbNumber of Beads 7Distance between beads 20Width 8Height 10Thickness of the part 4Beads’ thickness 4Optistruct Usage - DOEDesign Modification Variables Outcomingof the DOEparametersFindings of theDOE
  9. 9. DOE findings – examplesBead Width Beads HeightBeads Distance Beads Number9EATC - E. Santini - 23/04/2013Lower isbetterLower isbetterLower isbetter
  10. 10. Test Case 1 - Initial DesignFunctional Requirements:-Maximum reversible deviations from the nominal geometry due to loads duringvehicle operation  10mm (at 250 km/h)- Maximum deflection of 5mm between the mounting points and a maximum of3mm of gap formation in the edges areas when the vehicle is at a standstill10EATC - E. Santini - 23/04/2013V=250 km/hDeformationLoad Case:Weight of the part + water absorbed during 24hSimulated for different area weight:(1400, 1200, 1000 gsm)Load Case:Aerodynamics Pressure at Vmax=250 km/hAFR=500 Ns/m3 (simulated for different area weight)Pmax= 1050 PaP140 km/h= 200 PaStandstillDeflection
  11. 11. Test Case 1 – Best practices- 3 Proposals -Exploiting thefixation pointsReinforcing theweakest areas of thepartOutcoming of the DOEparameters11EATC - E. Santini - 23/04/2013
  12. 12. 12DEFLECTION REDUCTION OF 46%INITIAL DESIGN NEW DESIGNDEFLECTION REDUCTION OF 56%INITIAL DESIGNDEFLECTION REDUCTION OF 41%INITIAL DESIGN NEW DESIGNNEW DESIGNEATC - E. Santini - 23/04/2013Outcoming of the DOEparametersReinforcing theweakest areas of thepartExploiting thefixation pointsTest Case 1 – Best practices- 3 Proposals - Standstill
  13. 13. 13Test Case 1 – Design Optimisation- Optistruct Designs - StandstillFree Opt° Pattern Opt°Complianceoptimizationcenter= 0.85mm reduction of 57%edge=0.88mm reduction of 42%Free Opt° Pattern Opt°Modalfrequenciesoptimizationcenter= 1.71mm reduction of 14%edge=0.71mm reduction of 48%EATC - E. Santini - 23/04/2013
  14. 14. Test Case 1Weight Reduction - Speed max14Optimization made fromthe aerodynamicspressure distributionDesign proposal fromdeveloped guidelinesOptistructtargetDeformation mapEATC - E. Santini - 23/04/2013Lower isbetterOptimization made from anuniform pressure distribution
  15. 15. Test Case 2 – Optistruct ApplicationDesign Optimization = f(packaging space)15Blue area: 1.7mmYellow area: 5.2 mmBeads: 4.4 mmEATC - E. Santini - 23/04/2013 Matlab routine: calculating the distance ateach node from all the components to thebottom surface of the underbody Averaged distance at each element PSHELL with the computed thicknessassociated to the corresponding element Each color correspond to a differentPSHELL ID Optistruct topography optimization withelements constrained wrt the calculatedpackaging space.
  16. 16. Test Case 2 – Optistruct ApplicationCAE dedicated optimizationStatic deformation reduction between 25%-35% w.r.t. original design for the optimized solutionsDynamic behavior can be considerably changed/improved : eg: more than double natural freq. -specific vibration modes can be shifted (modal tuning)16EATC - E. Santini - 23/04/2013Optimization made according to the packaging space (calculated with an internal Matlab routine) Each shell of the FEM constrained to a maximum bead‘s height according to the packaging spacemeasured on the car model
  17. 17. Test Case 2Design ExamplesUnderbody Design ExamplesToday Design Design2Design 1Beading profile according to the packaging space17EATC - E. Santini - 23/04/2013Blue areas: material consolidated (e.g. 2mm at 1000gsm)Yellow areas: material unconsolidated (e.g. 4mm at 1000gsm)Brown areas: material unconsolidated, beading profile (e.g. 4mm at 1000gsm)Beading profile with different heightacross the part
  18. 18. Vehicle operationat 250 km/hStandstillconditionDeformation comparison= f (Designs)Vehicle operation (250 km/h), and at a standstill0%20%40%60%80%100%120%Aerodynamique Pressure(250 km/h)Standstill at the center of thepartStandstill at the edgesdeformation(%)foreachfunctionalrequirementOriginal DesignDesign 1Design 2Design 2 performs better than the design 1particularly during vehicle operation(transversal beading design)Modal frequencies improved of 40% fordesign 1 and 50% for design 2Test Case 2Design Proposals - Deformation18EATC - E. Santini - 23/04/2013
  19. 19. 19Design modifications can reduce thestrain rate, and consequently anypossible failure issue.Modifying locally the geometryaround the fixation area, the strainrate decreases from 6% to 3-4%depending on the modification.Initial configuration Circular bead Transversal bead7 mm10 mmFixationpointTest Case 3 - Design modificationMaximum strain reduction – Fatigue AnalysisEATC - E. Santini - 23/04/2013
  20. 20. Conclusions- Design optimization allows even at low material density to achieve the functional requirements ofthe customers in terms of stiffness (Also multiparameter optimization)- Specific material mechanical properties can be further exploited by dedicated CAE shapeoptimization- Design optimization used to find the best generalized design features definition of underbody design guidelines, which can be used to:a) identify lightest solutions fulfilling functional requirements,b) reduce number of fixation points.20EATC - E. Santini - 23/04/2013
  21. 21. 21EATC - E. Santini - 23/04/2013Q&ATHANK YOU FOR YOUR ATTENTIONEmanuele SantiniProducts and Systems Simulation SpecialistProduct Acoustic and Thermal PerformanceAutoneum Management AG, CH-8406 Winterthuremanuele.santini@autoneum.com . www.autoneum.com
  22. 22. 22Underbody systems are defined as parts, which are added below the body of a car, with aerodynamic functions and with the aim ofimproving its protection and acoustic performances. Underbody parts are subject to a variety of loads during vehicle operation, whichdegrade their original performances. Thus, an accurate design of the underbody shape is needed, in order to preserve its correctfunctioning and optimize its performances. In particular, it would be desirable to reduce the deflection of the underbody part underoperating loads, while preserving the same bill of material (cost) or even reducing it.In this work, we study the best possible part profiles by making use of CAE optimization. Our study aims at defining design guidelines,which can be used by the product engineers in order to design parts with an optimal solution since the beginning of the development.Simulations have been carried out by using Altair optimization software “Optistruct”, with the objective of increasing the stiffness of thepanels, while reducing the compliance under aerodynamic load and increasing the resonance frequencies. For this purpose, atopography optimization has been performed for some shape patterns. More precisely, the different areas of the panels areconstrained to a different level of maximum dislocation, depending on the packaging space available. In this way, some “special”shapes have been found, which are applicable in a large variety of configuration panels.Finally, the optimization results allow us to propose different modification solutions (some of them have been prototyped), with theobjective to increase the flexural stiffness of our panels. A 20% weight reduction of the parts is achievable by these modifications, thusfulfilling the functional requirements with a minimal material part layout.Emanuele SantiniProducts and Systems Simulation SpecialistProduct Acoustic and Thermal PerformanceAutoneum Management AG, CH-8406 Winterthuremanuele.santini@autoneum.com . www.autoneum.comOPTIMIZED DESIGN OF VEHICLEUNDERBODY SYSTEMEATC - E. Santini - 23/04/2013