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Durability Analyses of Power Train Components considering real Life-and Production Influences

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Durability Analyses of Power Train Components considering real Life-and Production Influences

  1. 1. HTC Europe 2011, Bonn, Nov.8th 2011Durability Analyses of Power Train Componentsconsidering real Life- and Production InfluencesName: Axel WerkhausenDate: 11/08/11
  2. 2. Overview 1. Introduction 2. Regarding Casting Processes in Fatigue Analyses 3. Regarding Hardening Stresses in Fatigue Analyses 4. Advanced Fatigue Assessment of Welds 5. Fatigue Optimization considering Dynamics 6. ConclusionsDate: 17.10.2011 Author: Unger/Werkhausen 2
  3. 3. Examples of Production Influence on Fatigue Secondary DAS Casting process Surface boundary layer effects Sheet metal forming Short fiber anisotropy Diversity of weldingsDate: 17.10.2011 Author: Unger/Werkhausen
  4. 4. Overview 1. Introduction 2. Regarding Casting Processes in Fatigue Analyses 3. Regarding Hardening Stresses in Fatigue Analyses 4. Advanced Fatigue Assessment of Welds 5. Fatigue Optimization considering Dynamics 6. ConclusionsDate: 17.10.2011 Author: Unger/Werkhausen 4
  5. 5. Influence from the Casting Process Aluminum components Geometry Surface Material Stress Sand / permanent mold cast Die cast Moderate cooling rate High cooling rate Low turbulence, mixing High turbulence, mixing Inhomegenious material Very inhomogenious material defects, porosity, strengthDate: 17.10.2011 Author: Unger/Werkhausen 5
  6. 6. Casting Simulation Result - SDAS Secondary Sand and permanent DAS mold aluminum casting Seed Mold Wall Fatigue Limit Factor Free definition Grain Size available SDAS . Tsolid TcoolDate: 17.10.2011 Author: Unger/Werkhausen 6
  7. 7. Example: Aluminum Steering Knuckle Damage results with nominal material properties Minimum Life= 100%Date: 17.10.2011 Author: Unger/Werkhausen 7
  8. 8. Example: Aluminum Steering Knuckle Sand casting Gravity permanent mold casting SDAS=60-90 m SDAS=30-60 mDate: 17.10.2011 Author: Unger/Werkhausen 8
  9. 9. Example: Aluminum Steering Knuckle Damage results including casting influence Sand casting Gravity permanent mold casting Life = 20% Life = 67 %Date: 17.10.2011 Author: Unger/Werkhausen 9
  10. 10. Example: Aluminum Die Cast Engine Support Bracket Aluminum GD-AlSi9 Cu3 Part #5 FKM - Research Project # 12 043 (April 1, 1999 - March 30, 2002): „Lebensdauerberechnung von Bauteilen bei mehrachsiger Belastung“ „Fatigue Life Prediction of Components undergoing Multiaxial Loading“Date: 17.10.2011 Author: Unger/Werkhausen 10
  11. 11. Correlation Simulation / Testing Engine Support Bracket, GD-AlSi9 Cu3, Load Case Fx Test-Results/BMW Test-Results/BMW Local strain- Load amplitude Fx [kN] life methods fine coarse Test FEMFAT local stress-life concept Load cycles (related to Fx)  Correlation factor ~ 100 is not satisfyingDate: 17.10.2011 Author: Unger/Werkhausen 11
  12. 12. Aluminum Die Cast Pores / Layers Further investigations by AK-13 during 2003-2004 Dr. Genbao Zhang, Volkswagen Conclusion  Nescessity for sub-surface assessement !Date: 17.10.2011 Author: Unger/Werkhausen 12
  13. 13. Boundary Layer Analysis Model Nearly pore-free skin Pore-effected inner volume Mesh size > boundary layer 3D-stress state How to analyze this situation ???Date: 17.10.2011 Author: Unger/Werkhausen 13
  14. 14. Boundary Layer Analysis Model  Calculation of sub-surface stress and stress gradientDate: 17.10.2011 Author: Unger/Werkhausen 14
  15. 15. Fatigue Analysis Engine Support BracketMaterial data – GD-AlSi9Cu3 Aluminum cast alloy for base material – GD-AlSi9Cu3 pore-free for boundary layer (modified strength data and S/N-curve) Specification Base material Pore-free material Young´s modulus 74.000 MPa Poisson´s ratio 0,3 Ultimate strength 240,0 MPa 366,6 MPa Yield strength 140,0 MPa 235,0 MPa Endurance stress limit 70,0 MPa 105,0 MPa Slope of the S/N-curve 12,0 10,0 Cycle limit 1,0E+7 2,0E+6Date: 17.10.2011 Author: Unger/Werkhausen 15
  16. 16. Fatigue Analysis Engine Support BracketStress amplitude (critical cutting plane) 75,7 MPa 53,1 MPa 39,7 MPa 35,3 MPa Surface Transition layer (below surface)  Stress drops considerably only in notchesDate: 17.10.2011 Author: Unger/Werkhausen 16
  17. 17. Fatigue Analysis Engine Support BracketEndurance safety factors 1,46 1,02 3,11 1,59 Surface / pore-free material Transition layer / base material  Critical location is below surface for both locationsDate: 17.10.2011 Author: Unger/Werkhausen 17
  18. 18. Fatigue Analysis Engine Support BracketEndurance safety factors 1,02 0,66 1,59 1,34 Transition layer / base material Without boundary layer  Results at surface are much too conservativeDate: 17.10.2011 Author: Unger/Werkhausen 18
  19. 19. Overview 1. Introduction 2. Regarding Casting Processes in Fatigue Analyses 3. Regarding Hardening Stresses in Fatigue Analyses 4. Advanced Fatigue Assessment of Welds 5. Fatigue Optimization considering Dynamics 6. ConclusionsDate: 17.10.2011 Author: Unger/Werkhausen 19
  20. 20. Influence of Hardening Stresses, Motivation Source: www..tribology.co.uk Typical tooth failure at the root of a tooth arising from alternating loads from the driving torque The tooth base is a weak spot! Source: www.oilanalysis.com Measurements at Simulation with test bench Finite Element Methods • expensive • prototype not • costly in terms of time necessary (prediction) • prototype necessaryDate: 17.10.2011 Author: Unger/Werkhausen 20
  21. 21. Example: Rear Axle Differential Gears Fine meshed tooth contact area 1 2 3 4 Coarse meshed body (10 – noded tetrahedral elements) 1 4 Fine meshed area for contact evaluation and hardening (linear hexahedral elements)Date: 17.10.2011 Author: Unger/Werkhausen 21
  22. 22. The Finite Element Models Hybrid mesh: •1st order hexahedron layers at the tooth surface • Coarse tetrahedral 2nd order mesh for gear body Bevel side gear: Intermediate gear:Date: 17.10.2011 Author: Unger/Werkhausen 22
  23. 23. The Simulation ApproachSketch of a damage-simulation: Load - Time - History Stress - Time - History Moment Stress Finite Element Stress Analysis Abaqus Standard V6.8 Time Time Damage Finite Element Simulation Analysis Total Hardening Thermal Strains Damage FEMFAT V4.7c - Stresses Module Abaqus Standard TransMAX V6.8Date: 17.10.2011 Author: Unger/Werkhausen 23
  24. 24. The Hardening Process – Volume Increase Work - hardening: 1. Step: slow warming (path – a) 2. Step: fast cooling – down (path – b) Permanent volume - increase due to hardening process! Change of crystal- structure: a b Ferrit Austenit Martensit 910°CDate: 17.10.2011 Author: Unger/Werkhausen 24
  25. 25. Simulation of the Hardening Stresses V  L  L0 1    T  3 3 3Increase of volume:  L0 1  3  T   3 .An artificial temperature difference is applied to increase the volume.Induced residual stresses due to hardening process: 98 % 100 % 100% 0%Date: 17.10.2011 Author: Unger/Werkhausen 25
  26. 26. The Damage Simulation Material data: hardening layer Material data: basic materialSource: dissertation Tobias Hertter- „Rechnerischer Festigkeitsnachweis Source: FEMFAT data base (FKM & Material generator)der Ermüdungstragfähigkeit vergüteter und einsatzgehärteter Stähle“,2003 and FEMFAT material generatorDate: 17.10.2011 Author: Unger/Werkhausen 26
  27. 27. Damage Results at the Intermediate Gear 0.07 0.14 With hardening stresses! Without hardening stresses!Date: 17.10.2011 Author: Unger/Werkhausen 27
  28. 28. Damage Results at the Bevel Gear 0.016 0.032 With hardening stresses! Without hardening stresses!Date: 17.10.2011 Author: Unger/Werkhausen 28
  29. 29. Overview 1. Introduction 2. Regarding Casting Processes in Fatigue Analyses 3. Regarding Hardening Stresses in Fatigue Analyses 4. Advanced Fatigue Assessment of Welds 5. Fatigue Optimization considering Dynamics 6. ConclusionsDate: 17.10.2011 Author: Unger/Werkhausen 29
  30. 30. Sensitivity Analysis of Welded Structures Design Verification Design Dynamic multi body (CAD) simulation (MBS) Full scale fatigue test Iterative FE-model Dynamic load- time histories Optimization process FE-analysis Component prototype Sensitivity analysis Numerical Sensitive / critical weld seams fatigue life analysis Design change Process optimization Robust DesignDate: 17.10.2011 Author: Unger/Werkhausen 30
  31. 31. Weld Geometry DefinitionParameter variations: • Degree of weld penetration – h h  d/t • Seam thickness – a • Seam inclination angle –   Weld gap • Weld gap Example: T-Joint 90° Parameter – Better Quality Standard Quality Worse Quality T-Joint 90° (Quality class B) (Quality class C) (Quality class D) Degree of weld penetration - h 100% 50% 0% Seam thickness - a 1.5 t t 0.7 t Seam inclination angle -  110° 100° 90° Weld gap (at 3mm thickness) 0mm 0.5mm 1.5mm  Determination of notch factors for weld databaseDate: 17.10.2011 Author: Unger/Werkhausen 31
  32. 32. Weld Geometry Definition T-Joint 90° T-Joint 45° Overlap joint HY seam, HV seam outside, Fillet weld Degree of weld penetration: 80% Degree of weld penetration: 100% (without weld gap) Standard Analysis Fillet weld with keyhole notch HY seam outside, Fillet weld Degree of weld penetration: 50% (with weld gap) Sensitivity Analysis 9Date: 17.10.2011 Author: Unger/Werkhausen 32
  33. 33. Standard vs. Sensitivity AnalysisExample 1) front cradle – front wheel drive vehicle Standard analysis Sensitivity analysis Damage [-] Sensitivity analysisDate: 17.10.2011 Author: Unger/Werkhausen 33 1
  34. 34. Standard vs. Sensitivity AnalysisExample 1) front cradle – front wheel drive vehicle Sensitivity factor Identification of sensitive / critical weld seams ( DSens  DS tan dard ) FSENS FSENS  ( DSens  DS tan dard ) DSens DSens 0 = no sensitivity 1 = very sensitive! <0 = ImprovementDate: 17.10.2011 Author: Unger/Werkhausen 34
  35. 35. Overview 1. Introduction 2. Regarding Casting Processes in Fatigue Analyses 3. Regarding Hardening Stresses in Fatigue Analyses 4. Advanced Fatigue Assessment of Welds 5. Fatigue Optimization considering Dynamics 6. ConclusionsDate: 17.10.2011 Author: Unger/Werkhausen 35
  36. 36. Fatigue Optimization considering Dynamics Start FE Solver FE-Model Dynamic Mode Shapes Loads Modal 25 20 15 10 5 0 MBS Stresses -5 -10 -15 -20 -25 Modal -30 Coordinates Adapted FEMFAT FE-Model Damage TOSCA Yes Stop Condition No New Design Process controlled fulfilled? by TOSCADate: 17.10.2011 Author: Unger/Werkhausen 36
  37. 37. Optimization of a Lower Suspension ArmConsideration of system dynamics FE model of the design space MBS-model Load time series of forces and moments at the wheelDate: 17.10.2011 Author: Unger/Werkhausen 37
  38. 38. Optimization of a Lower Suspension Armregarding Fatigue and Dynamics Optimized original 8% less weightDate: 17.10.2011 Author: Unger/Werkhausen 38
  39. 39. Conclusions • The production process can have a significant influence to fatigue results • The SDAS parameter distribution can be used for regarding porosity at Aluminium sand-and mold components • For aluminium die casting components a special boundary layer model is used to consider surface effects • The inclusion of the hardening stresses is essential for trustable damage results • Production related weld geometry deviations can be taken into account in fatigue simulation using sensitivity analysis • Critical weld joints can be identified for further optimization • Multi disziplinary optimization including fatigue becomes practicableDate: 17.10.2011 Author: Unger/Werkhausen 39
  40. 40. Thank you for your Attention !Date: 17.10.2011 Author: Unger/Werkhausen 40

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