May 14-15, 2014 2014 HBM nCode Products User Group Meeting 2014 HBM nCode Products User Group Meeting ®2014 HBM www.ncode.com Livonia, MI (USA) May 14-15, 2014 2014 HBM nCode Products User Group Meeting 2014 HBM nCode Products User Group Meeting Design of Components for High Temperatures and Thermo-Mechanical Fatigue (TMF) Dr. Andrew Halfpenny Chief Technologist HBM – nCode Product Division ®2014 HBM www.ncode.com Livonia, MI (USA) May 14-15, 2014 2014 HBM nCode Products User Group Meeting Contents 2014 HBM nCode Products User Group Meeting 1. ®2014 HBM Thermal Loading Classification • Iso‐thermal and Transient‐thermal loading • Creep and Non‐creep 2. The Physics of Fatigue and Creep 3. The Chaboche Creep and Fatigue curves 4. Case Studies • Laboratory testing • Hot Engine Exhaust Component www.ncode.com Livonia, MI (USA) May 14-15, 2014 2014 HBM nCode Products User Group Meeting Livonia, MI (USA) What is Transient-thermal Loading? 2014 HBM nCode Products User Group Meeting Exhaust Manifold, Cylinder Head & Turbocharger • Engine stop‐start thermal cycles • Constrained thermal expansion large stress cycle • Coupling between temperature and stress cycles phase important In-phase 4 ®2014 HBM www.ncode.com May 14-15, 2014 2014 HBM nCode Products User Group Meeting Livonia, MI (USA) What is Iso-thermal? 2014 HBM nCode Products User Group Meeting Exhaust muffler • Constant high temperature • Fatigue loading primarily due to mechanical load or vibration • Note: thermal transients can be treated as separate duty cycle events Mechanical Loading 5 ®2014 HBM www.ncode.com May 14-15, 2014 2014 HBM nCode Products User Group Meeting Livonia, MI (USA) The Physics of Fatigue and Creep • • • • Tensile Fatigue Creep Oxidation Interaction 2014 HBM nCode Products User Group Meeting Failure mechanisms • Tensile properties reduce with increasing temperature increased likelihood of local plasticity • Fatigue properties reduce with increasing temperature 6 ®2014 HBM www.ncode.com May 14-15, 2014 2014 HBM nCode Products User Group Meeting Livonia, MI (USA) The Physics of Fatigue and Creep 2014 HBM nCode Products User Group Meeting Creep: Inelastic deformation and damage due to combination of high temperature and stress levels Diffusing atoms Original grain shape Min shear stress Max shear stress Melting point Creep New grain shape ½ melting point Void growth by diffusion Voids on grain boundary No Creep Nabarro‐Herring Creep • Atoms diffuse from stressed face to unstressed face Creep rupture • Voids develop on grain boundaries • Voids grow through atom diffusion and void coalescence Room temp 0 Kelvin 7 ®2014 HBM www.ncode.com May 14-15, 2014 2014 HBM nCode Products User Group Meeting Livonia, MI (USA) FE Modelling Challenges – Plasticity & Creep 2014 HBM nCode Products User Group Meeting Moderate temperature High temperature c1 Stress proportional to spring extension k1 k1 Applied static displacement Elasto‐plastic deformation Elasto‐viscoplastic deformation Reduced tensile properties at elevated temperature leads to increased chance of plasticity Stress relaxation over time caused by Creep deformation 8 ®2014 HBM www.ncode.com May 14-15, 2014 2014 HBM nCode Products User Group Meeting Livonia, MI (USA) 2014 HBM nCode Products User Group Meeting Thermal Loading Classification Steady‐state temperature High temperature Creep Melting point Elasto‐viscoplastic FE Linear/Time step FE Chaboche Cycle‐by‐cycle + Chaboche Creep No Creep ½ melting point Room temp 0 Kelvin Transient temperature Chaboche Transient + Chaboche Creep Cylinder head (hot side) Manifold Turbo Linear FE Time step FE Chaboche Cycle‐by‐cycle Chaboche Transient Exhaust system Cylinder head (cold side) Moderate temperature 9 ®2014 HBM www.ncode.com May 14-15, 2014 2014 HBM nCode Products User Group Meeting Contents 2014 HBM nCode Products User Group Meeting 1. ®2014 HBM Thermal Loading Classification • Iso‐thermal and Transient‐thermal loading • Creep and Non‐creep 2. The Physics of Fatigue and Creep 3. The Chaboche Creep and Fatigue curves 4. Case Studies • Laboratory testing • Hot Engine Exhaust Component www.ncode.com Livonia, MI (USA) May 14-15, 2014 2014 HBM nCode Products User Group Meeting Livonia, MI (USA) 2014 HBM nCode Products User Group Meeting Iso-Thermal Fatigue Analysis • Mechanical loading superimposed on constant temperature • User choice of temperature • Temp = max(Ti) • Temp = min(Ti) • Temp = median(Ti) • Temp = T(t) • Max temp over stress cycle i.e. time specified by user • Interpolate fatigue properties based on multiple temperature curves 11 ®2014 HBM www.ncode.com May 14-15, 2014 2014 HBM nCode Products User Group Meeting Livonia, MI (USA) Chaboche Transient Thermal Fatigue Model Temperature-dependent fatigue curves • Collapse temperature‐dependent fatigue 2014 HBM nCode Products User Group Meeting curves on to a single ‘master’ curve • Use temperature‐compensated stress time signal Chaboche master fatigue curve 12 ®2014 HBM www.ncode.com May 14-15, 2014 2014 HBM nCode Products User Group Meeting Livonia, MI (USA) 2014 HBM nCode Products User Group Meeting Chaboche Local Stress vs. Fatigue Curve Non-linear damage evolution • Local Stress from FEA • Curve incorporates: • • Mean stress correction • Low‐cycle fatigue • High‐cycle fatigue • Fatigue limit Uses industry standard iso‐thermal fatigue testing to obtain material properties 13 ®2014 HBM www.ncode.com May 14-15, 2014 2014 HBM nCode Products User Group Meeting Livonia, MI (USA) Chaboche Local Stress vs. Fatigue Curve Goodman/Morrow mean stress correction 2014 HBM nCode Products User Group Meeting Low cycle fatigue limit Basquin’s SN equation Fatigue durability limit • Local Stress from FEA • Curve incorporates: • • Mean stress correction • Low‐cycle fatigue • High‐cycle fatigue • Fatigue limit Low cycle limit strength Uses industry standard iso‐thermal Fatigue limit fatigue testing to obtain material properties 14 ®2014 HBM www.ncode.com May 14-15, 2014 2014 HBM nCode Products User Group Meeting Livonia, MI (USA) 2014 HBM nCode Products User Group Meeting Solvers – New Chaboche creep model • Chaboche creep curve • Rupture time obtained from: A = intercept of creep curve r = creep exponent k = non-linear evolution coefficient 15 ®2014 HBM www.ncode.com May 14-15, 2014 2014 HBM nCode Products User Group Meeting Contents 2014 HBM nCode Products User Group Meeting 1. ®2014 HBM Thermal Loading Classification • Iso-thermal and Transient-thermal loading • Creep and Non-creep 2. The Physics of Fatigue and Creep 3. The Chaboche Creep and Fatigue curves 4. Case Studies • Laboratory testing • Hot Engine Exhaust Component www.ncode.com Livonia, MI (USA) May 14-15, 2014 2014 HBM nCode Products User Group Meeting Livonia, MI (USA) Case Study – ISO-thermal Creep & Fatigue Analysis ®2014 HBM Chaboche Fatigue Curve Comparison of experimental and predicted lives 3 7 110 110 Chaboche fatigue curve Measured test data 6 110 Predicted lives Stress amplitude (MPa) 2014 HBM nCode Products User Group Meeting 600 degC 5 110 4 110 5x scatter 10x scatter 3 110 100 10 100 3 110 4 110 5 110 110 6 7 110 Number of cycles to failure (Nf) 100 100 3 110 4 110 110 5 Experimental lives www.ncode.com 6 110 7 110 May 14-15, 2014 2014 HBM nCode Products User Group Meeting 2014 HBM nCode Products User Group Meeting Case Study – Transient-thermal Creep & Fatigue ®2014 HBM www.ncode.com Livonia, MI (USA) May 14-15, 2014 2014 HBM nCode Products User Group Meeting 2014 HBM nCode Products User Group Meeting Case Study – EGR Valve Housing ®2014 HBM • Accelerated TMF Test • Consider analyses: • Chaboche Iso‐thermal • Chaboche Creep • Chaboche Transient www.ncode.com Livonia, MI (USA) May 14-15, 2014 2014 HBM nCode Products User Group Meeting Case Study – EGR Valve Housing Chaboche Iso‐thermal interpolated test region Local Stress well within Local Stress 2014 HBM nCode Products User Group Meeting • Stress & temperature Chaboche Transient • Stress & temperature well within interpolated test region ®2014 HBM www.ncode.com Livonia, MI (USA) May 14-15, 2014 2014 HBM nCode Products User Group Meeting Livonia, MI (USA) 2014 HBM nCode Products User Group Meeting Case Study – EGR Valve Housing ®2014 HBM Cycles to Failure Chaboche Iso‐thermal Chaboche Transient Chaboche Creep Experimental test ~500 Based on worst case temperature No account of stress phase ~1000 No damage ~1000 • All failure sites correctly identified • Fatigue life within a factor of 2 www.ncode.com At critical locations, stress is out‐of‐ phase with temperature longer life May 14-15, 2014 2014 HBM nCode Products User Group Meeting Livonia, MI (USA) Conclusion 2014 HBM nCode Products User Group Meeting Iso‐thermal fatigue • Nominal stress (SN) • Local strain (EN) • Local stress (Chaboche) Creep • Larson‐Miller • Chaboche creep Thermo‐Mechanical fatigue • Chaboche combined creep‐fatigue Finite Element Analysis • Linear elastic • Elastic‐plastic • Elasto‐visco‐plastic (EVP) 22 ®2014 HBM www.ncode.com May 14-15, 2014 2014 HBM nCode Products User Group Meeting Thank you! Dr. Andrew Halfpenny Chief Technologist T: +44 (7968) 288760 E: [email protected] 2014 HBM nCode Products User Group Meeting ®2014 HBM www.ncode.com Livonia, MI (USA)
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