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UK ATC 2015: Optimised Rear Twist Beam Design
The document discusses the optimization of rear twist beam (RTB) designs for vehicle suspensions. It describes Gestamp's process of using optimization software to design RTBs that meet requirements for roll stiffness, roll steer, durability, packaging space, and mass. The process eliminates initial trial and error CAD work. It then focuses on optimizing the reinforcer length, torsion element gauge, and local edge shapes to minimize stress and mass while satisfying the rollover and fatigue targets. The optimized design process allows Gestamp to quickly develop competitive low-cost, low-mass RTB designs.
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Introduction to the Optimized Rear Twist Beam (RTB) design, highlighting Gestamp's global presence and chassis products.
Introduction of the RTB suspension system's components, advantages, and the design's basis.
Discussion on important inputs defining RTB geometry including roll stiffness, roll steer, and space constraints.
Gestamp's collaboration with Altair to enhance RTB design processes through optimization and elimination of trial and error.
Balancing roll stiffness and antiphase durability through the optimization of length and gauge of structural elements.
Focus on shape optimization iterations to reduce stress in the design, achieving a 14% reduction in maximum stress.
Summary of how the optimized design process enables quick adaptation and realization of cost-effective RTB systems.
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UK ATC 2015: Optimised Rear Twist Beam Design
- 1. 16/6/15 Optimised Rear TwistBeam Design Altair Conference
- 2. 1©2015 GESTAMP Gestamp GlobalLocations Optimized Rear Twist Beam Design
- 3. 2©2015 GESTAMP Gestamp ChassisProducts Optimization based Chassis Design
- 4. 3©2015 GESTAMP RTB SuspensionSystem Rigid trailing arms/side rails with Body Mounts Torsion Element Optimized Rear Twist Beam Design Reinforcer Image from Wikipedia
- 5. 4©2015 GESTAMP Optimized RearTwist Beam Design Advantages of RTB Rear Suspension Image from a2mac1.com
- 6. 5©2015 GESTAMP Optimized RearTwist Beam Design Several interlinked targets, which depend on shape, position and gauge of structural members
- 7. 6©2015 GESTAMP Gestamp RTBDesign Process • Initial Information Optimized Rear Twist Beam Design
- 8. 7©2015 GESTAMP Key InputsDefining Basic RTB Geometry Roll Stiffness = C/∆θ Optimized Rear Twist Beam Design Roll Stiffness A measure of how much the RTB resists the rolling moment of the vehicle. Resistance provided by the torsional rigidity of the Torsion Element.
- 9. 8©2015 GESTAMP Key InputsDefining Basic RTB Geometry Optimized Rear Twist Beam Design Roll Stiffness A A Section Through A - A Position (x,z) Shape Gauge Reinforcer Length
- 10. 9©2015 GESTAMP Key InputsDefining Basic RTB Geometry Optimized Rear Twist Beam Design Roll Steer Steer angle change of rear wheels during vehicle cornering. This can be used to generate “Roll Understeer”. Turn Direction
- 11. 10©2015 GESTAMP Key InputsDefining Basic RTB Geometry Optimized Rear Twist Beam Design A A Section Through A - A Position (x,z) Shape Roll Steer Gauge
- 12. 11©2015 GESTAMP Key InputsDefining Basic RTB Geometry Optimized Rear Twist Beam Design Available Package Space RTB Designs require minimal space, but the positioning of the fuel tank/spare wheel can influence the design. Image from a2mac1.com
- 13. 12©2015 GESTAMP Optimized RearTwist Beam Design Gestamp have worked with Altair to develop a method of quickly producing RTB concept designs which meet K&C and package requirements.
- 14. 13©2015 GESTAMP RTB Toolbox OptimizedRear Twist Beam Design Optimisation
- 15. 14©2015 GESTAMP RTB Toolbox DOEsensitivity study Optimized Rear Twist Beam Design Optimisation Design Variables
- 16. 15©2015 GESTAMP Gestamp RTBDesign Process • Initial “Trial and Error” CAD loop eliminated. Optimized Rear Twist Beam Design
- 17. 16©2015 GESTAMP Optimized RearTwist Beam Design Next Design Stage: Optimisation for Antiphase Durability Target
- 18. 17©2015 GESTAMP Target Conflict:Roll Stiffness and Antiphase Durability There is a relationship between the Roll Stiffness and Fatigue Life for the Antiphase Durability Load Case. Long Reinforcer Thin Gauge Torsion Element Short Reinforcer Thick Gauge Torsion Element Mass Stress z y Optimized Rear Twist Beam Design
- 19. 18©2015 GESTAMP Optimized RearTwist Beam Design There is an optimum combination of reinforcer length and torsion element gauge for a given Roll Stiffness and Fatigue requirement.
- 20. 19©2015 GESTAMP Optimisation ofBasic Concept Optimized Rear Twist Beam Design VARIABLES Length and profile of reinforcer SectionGauge OBJECTIVE
- 21. 20©2015 GESTAMP Optimized RearTwist Beam Design
- 22. 21©2015 GESTAMP Optimized RearTwist Beam Design
- 23. 22©2015 GESTAMP Optimised ConceptMeeting K&C and Durability Requirement Optimum Length and shape Optimum Gauge and Section Optimized Rear Twist Beam Design Mass Minimised A A Section Through A - A
- 24. 23©2015 GESTAMP Gestamp RTBDesign Process Basic Design complete Optimized Rear Twist Beam Design
- 25. 24©2015 GESTAMP 40mm AntiphaseRolling Load Case - Von Mises Stress (MPa) Local Shape Optimisation for Stress Reduction Optimized Rear Twist Beam Design Max = 295MPa
- 26. 25©2015 GESTAMP Moveable controlpoint defining edge shape • Variables - xy grid co-ordinates of 7control points defining a curve. • Constraints - Don’t move too far (within bounds of feasible design) • Objective - minimize the maximum stress in any of the measured elements Record stress in edge elements Shape Optimisation for Stress Reduction Optimized Rear Twist Beam Design
- 27. 26©2015 GESTAMP Moveable controlpoint defining edge shape Shape Optimisation for Stress Reduction – Iteration 1 Optimized Rear Twist Beam Design
- 28. 27©2015 GESTAMP Shape Optimisationfor Stress Reduction – Iteration 2 Optimized Rear Twist Beam Design
- 29. 28©2015 GESTAMP Shape Optimisationfor Stress Reduction – Iteration 3 Optimized Rear Twist Beam Design
- 30. 29©2015 GESTAMP Shape Optimisationfor Stress Reduction – Iteration 5 Optimized Rear Twist Beam Design
- 31. 30©2015 GESTAMP 295MPa 40mm twistloadcase - Von Mises Stress (MPa) Iteration 0 40mm twist loadcase - Von Mises Stress (MPa) Iteration 9 295MPa 255MPa Shape Optimisation for Stress Reduction Optimized Rear Twist Beam Design 14% Stress Reduction
- 32. 31©2015 GESTAMP Gestamp RTBDesign Process Benefit of using an Optimisation led approach Optimized Rear Twist Beam Design Typical RTB Design Process
- 33. 32©2015 GESTAMP Conclusions Optimized RearTwist Beam Design • This design process has allowed Gestamp to react quickly and produce competitive, low cost, low mass designs for RTB suspension systems. • Gestamp have recognised the potential for mass reduction through optimisation of the U section design.
- 34. ©2013 GESTAMP AUTOMOCIÓN OptimisedRear Twist Beam Design 16/06/15 A Charlesworth