Improving the assessment quality of a fatigue analysis
0 likes513 views
1) The document describes a workflow for improving fatigue analysis quality through virtual iteration of multi-body system (MBS) models using load data from physical testing. 2) Sensors measure response data like accelerations, displacements, and strains during physical testing, which is analyzed to generate load data to drive virtual MBS models through an iterative process. 3) The virtual iteration technique aims to match simulated response data from the MBS model with the physical test response data, allowing internal loads and stresses from the MBS to be used for more accurate fatigue analysis.
Improving the assessment quality of a fatigue analysis
- 1. © ECS / Disclosure or duplication without consent is prohibited Improving the assessment quality of a fatigue analysis ALTAIR Motion solve, FEMFAT LAB virtual iteration and FEMFAT
- 2. © ECS / Disclosure or duplication without consent is prohibited General Workflow Author: FEMFAT SUPPORT 2Date: 05.05.2015 Application & calibration Data acquisition on proving ground Load data analysis Fatigue testing Fatigue analysis Virtual iteration MBS model Workflow of fatigue testing and analysis based on road load data M U L T I P H Y S I C W O R K F L O W
- 3. © ECS / Disclosure or duplication without consent is prohibited General Workflow Author: FEMFAT SUPPORT 3Date: 05.05.2015 Acceleration Typical responses • Accelerations – 1-axial – 3-axial • Displacements – Draw wire displacement sensor • Frame torsion • Strains (directly/calibrated to forces) – Axle – Ball joint – Link – Rod – Spring – Stabilizer • Load cells – Mount • Wheel force transducers Displacement Strain – ball jointStrain – twist beam Load cell Wheel force transducer
- 4. © ECS / Disclosure or duplication without consent is prohibited General Workflow Author: FEMFAT SUPPORT 4Date: 05.05.2015 Workflow of fatigue testing and analysis based on road load data Application & calibration Data acquisition on proving ground Load data analysis Fatigue testing Fatigue analysis Virtual iteration MBS model M U L T I P H Y S I C W O R K F L O W
- 5. © ECS / Disclosure or duplication without consent is prohibited • FEMFAT LAB – Load data analysis software • Module Virtual Iteration: – Load data generation for simulation models based on measurement data (test track or test bench) • General approach – Generate external load based on internal, measured response • Same approach as the iteration process in the laboratory (test bench) • Excellent convergence between measurement and simulation • Method is automated for – MotionSolve and additional 3rd party MBD products General Workflow Author: FEMFAT SUPPORT 5Date: 05.05.2015 black…measurement red…...simulation
- 6. © ECS / Disclosure or duplication without consent is prohibited General Workflow Author: FEMFAT SUPPORT 6Date: 05.05.2015 Workflow of fatigue testing and analysis based on road load data Application & calibration Data acquisition on proving ground Load data analysis Fatigue testing Fatigue analysis Virtual iteration MBS model M U L T I P H Y S I C W O R K F L O W
- 7. © ECS / Disclosure or duplication without consent is prohibited General Workflow Author: FEMFAT SUPPORT 7Date: 05.05.2015 • MotionSolve model of front axle of a passenger car (half axle) • Computing internal forces for fatigue analysis of the knuckle with • Measurement signals from test track • Desired (measurement) • Damper force • Ball joint force longitudinal • Ball joint force lateral • Tie rod force axial • Spring displacement (used for model-check) • Goal: load at wheel (4 channels) • Vertical displacement (wheel center) • Longitudinal force (wheel center) • Steering torque (wheel center) • Lateral force (tire patch)
- 8. © ECS / Disclosure or duplication without consent is prohibited General Workflow Author: FEMFAT SUPPORT 8Date: 05.05.2015 Measurement signals (responses) Damper force Tie rod force Ball joint forces Spring displacement MBS: requests
- 9. © ECS / Disclosure or duplication without consent is prohibited General Workflow Author: FEMFAT SUPPORT 9Date: 05.05.2015 Workflow of fatigue testing and analysis based on road load data Application & calibration Data acquisition on proving ground Load data analysis Fatigue testing Fatigue analysis Virtual iteration MBS model M U L T I P H Y S I C W O R K F L O W
- 10. © ECS / Disclosure or duplication without consent is prohibited FEMFAT LAB vi Introduction Author: FEMFAT SUPPORT 10Date: 05.05.2015 Response Often simply and cheaply measureable • Accelerations • Displacements (relative) • Strains • Forces (internal) Drive High effort or not measureable • Forces (external) • WFT • Load cell • Strain gauges • Displacements (absolute) Inverse non-linear problem find load for given response MotionSolve Input un Output yn Load (drive) Desired (response)
- 11. © ECS / Disclosure or duplication without consent is prohibited FEMFAT LAB vi Introduction Author: FEMFAT SUPPORT 11Date: 05.05.2015 MotionSolve Input un Output yn Load (drive) Desired (response) Calculation of the transfer function (MBS): F(s) = y0(s) / u0(s) noise signal and its response Calculation of first drive: u1(s)= F-1(s) yDesired(s) Calculation of further iterations: un+1(s)=un(s)+ F-1(s) (yDesired(s) – yn(s))
- 12. © ECS / Disclosure or duplication without consent is prohibited FEMFAT LAB vi Introduction Author: FEMFAT SUPPORT 12Date: 05.05.2015 Iteration process un+1 = un + F -1 ( yDesired - yn ) 1. Noise 2. Response of noise 6. Response = desired 5. Response 3. Transfer function 4. Drive signal
- 13. © ECS / Disclosure or duplication without consent is prohibited FEMFAT LAB vi Results Author: FEMFAT SUPPORT 13Date: 05.05.2015 Results: 10. iteration, rough road
- 14. © ECS / Disclosure or duplication without consent is prohibited FEMFAT LAB vi Results Author: FEMFAT SUPPORT 14Date: 05.05.2015 Damper force – time domain 15th to 20th second Ball joint force lateral – time domain 15th to 20th second Ball joint force longitudinal – time domain 15th to 20th second Tie rod force axial – time domain 15th to 20th second black…measurement red…...simulation Results: 10. iteration, rough road
- 15. © ECS / Disclosure or duplication without consent is prohibited FEMFAT LAB vi Results Author: FEMFAT SUPPORT 15Date: 05.05.2015 Damper force - frequency domain Ball joint force lateral - frequency domain Ball joint force longitudinal - frequency domain Tie rod force axial - frequency domain Results: 10. iteration, rough road black…measurement red…...simulation
- 16. © ECS / Disclosure or duplication without consent is prohibited FEMFAT LAB vi Results Author: FEMFAT SUPPORT 16Date: 05.05.2015 Spring displacement (model check) Spring displacement – time domain Spring displacement – time domain 15th to 20th second Spring displacement – frequency domain Results: 10. iteration, rough road black…measurement red…...simulation
- 17. © ECS / Disclosure or duplication without consent is prohibited FEMFAT LAB vi Results Author: FEMFAT SUPPORT 17Date: 05.05.2015 Results: 10. Iteration – relative damage values (signal based) Relative damage comparison simulation to measurement 1,02 1,03 0,99 0,970,97 0,90 0,95 1,00 1,05 1,10 Damper force Bolt force lateral Bolt force longitudinal Tie rod force Spring deflection relativedamagevalue
- 18. © ECS / Disclosure or duplication without consent is prohibited General Workflow Author: FEMFAT SUPPORT 18Date: 05.05.2015 Workflow of fatigue testing and analysis based on road load data Application & calibration Data acquisition on proving ground Load data analysis Fatigue testing Fatigue analysis Virtual iteration MBS model M U L T I P H Y S I C W O R K F L O W
- 19. © ECS / Disclosure or duplication without consent is prohibited Fatigue analysis Author: FEMFAT SUPPORT 19Date: 05.05.2015 Internal forces of MOTION SOLVE using VI: Rough road Specimen material data FE structure & FE stresses for each load case Multi axial fatigue assessment RESULT: Damage Values
- 20. © ECS / Disclosure or duplication without consent is prohibited Fatigue analysis Author: FEMFAT SUPPORT 20Date: 05.05.2015 Stress Tensors Material Properties Stress Gradient Mean Stress Influence MultiAXial Load Technological Influences Size Influence Temperature Influence PLASTic Deformations SPOT Joints s Anisotropical Behaviour of Arc WELDs etc. S/N1 modified by FEMFAT Load Cycles StressAmplitude S/N material from specimen tests
- 21. © ECS / Disclosure or duplication without consent is prohibited Fatigue analysis Author: FEMFAT SUPPORT 21Date: 05.05.2015 Stress Tensors Stress Gradient Mean Stress Influence MultiAXial Load Temperature Influence PLASTic Deformations etc. Influences in FEMFAT Finally : Component S/N curve including all influences FOR EACH NODE Stress Amplitude Load cycles Mean Stress Stress Amplitude UTSUCS Specimen Material Data Mean Stress Stress Amplitude UTSUCS Load cycles
- 22. © ECS / Disclosure or duplication without consent is prohibited Fatigue analysis Author: FEMFAT SUPPORT 22Date: 05.05.2015 • Transformation of all stress tensors into several planes (2D,3D) • Filtering of interesting planes • Generation of the load histories of the stress components • Rainflow counting in all selected planes • Damage analysis (Influence Parameter Method) • The cutting plane with maximum damage is assumed to be the critical plane for fatigue failure )( )( )( zzzzyyzxxz yzzyyyyxxy xzzxyyxxxx nnne nnne nnne σσσ σσσ σσσσ ++×+ ++×+ ++×= γ σa n σm n τ a τ m ϕ
- 23. © ECS / Disclosure or duplication without consent is prohibited Result comparison Author: FEMFAT SUPPORT 23Date: 05.05.2015 Crack observed after 97 h Test bench Crack predicted after 28 h FEMFAT with WFT Crack predicted after 60 h FEMFAT with Virtual Iteration
- 24. © ECS / Disclosure or duplication without consent is prohibited Conclusion • Fully automated co-simulation FEMFAT LAB and MotionSolve • Easier and cheaper measurements can be used to get a better correlation • Including FE-structures in a MotionSolve model can account also for dynamic effects in the fatigue analysis • Including a MotionSolve simulation can also account for nonlinear effects (nonlinear dampers, springs…) • No limitations for the used flex body co-simulation (attachment parts to full vehicle) • Major increase of the accuracy in fatigue with FEMFAT with a minor increase of the FEA simulation effort • FEMFAT is available in the partner program • FEMFAT LAB will follow soon ! Author: FEMFAT SUPPORT 24Date: 05.05.2015
- 25. © ECS / Disclosure or duplication without consent is prohibited The future is ours to make. Author: FEMFAT SUPPORT 25Date: 05.05.2015