EngineeringAspectsyofFatigueLifePredictionAug26

EngineeringAspectsyofFatigueLifePredictionAug26 -...

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Engineering Aspects of Fatigue Life Prediction Dan Lingenfelser 100 Research Blvd an lingenfelser@hbmncode com Dan.lingenfelser@hbmncode.com 248-854-7946 1
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Background Work Experience – Heavy equip operator/mechanic – 35 years at Caterpillar – Design, Test, Supplier Quality, Structures Technology 009 Retired and orking “Part Time” at HBM nCode 2009 Retired and working “Part Time” at HBM nCode Structural Testing of Components & Materials Track Bushings, Roller Shafts, Torsion Shafts, Track Links, Con Rods, Fuel Injectors, STBF Gears, Weld Samples, etc. New Products, Process, and Product Improvement Primarily Metallic Materials Jan 2000 – Oct. 2005 - 7,501,378,261 Load Cycles; 5,718 Test Articles onsulting & Education on Structural Design & Bolted Joints Consulting & Education on Structural Design & Bolted Joints 2006 - 2009 Technical Expert – Fatigue Life Prediction – VPD Technical Society Activities AE atigue Design & Evaluation Committee SAE Fatigue Design & Evaluation Committee – ASTM – E08 Fatigue & Fracture • E08.04 Applications – ISO TC164/SC5 Mechanical Testing/Fatigue 2
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h t i d We hope to avoid this 3
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aper Clip Exercise Paper Clip Exercise esults 40 160 180 200 Group1 Group 2 Group 3 Results Amplitude Cycles A Cycles B 90 90 90 90 0 80 100 120 140 Degrees 45 45 45 45 22.5 22.5 0 20 40 60 024681 0 1 2 l 22.5 22.5 One test is worth 1,000 pinions Reversals 4 opinions.
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Paper Clip Exercise One test is a sample of one 100 Results Amplitude Cycles A Cycles B 90 0 90 90 90 45 45 5 Amplitude 45 45 22.5 22.5 22.5 2 5 22.5 5 10 11 0 1 0 0 Cycles
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Typical Bushing Fatigue Test Simple Loading, Simple geometry, non homogeneous material Total life can include significant crack propagation 6
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Bushing Cycles to Crack Initiation 00 000 100,000 Initiation curves are not parallel & there appears to be endurance limit Load Range 10,000 ,000 0,000 00,000 ,000,000 0,000,000 Variability of 5x in life is common (within group) 7 1,000 10,000 100,000 1,000,000 10,000,000 Life (Cycles)
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Bushing Total Life to Failure 100,000 Ni/Nt Ranges from ~5%-99% Ni/Nt =f(processing,material, load) ange Load R Curves cross (different slopes) with different ranking than initiation curves 10,000 1,000 10,000 100,000 1,000,000 10,000,000 Life (Cycles) 8
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Bushing Life to Failure (2nd Size) 100,000 nge Load Ra 0 000 10,000 1,000 10,000 100,000 1,000,000 10,000,000 Cycles to failure 9
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Variability in Weld Life Performance – ½” Cruciform Weld life/strength is function of process Baseline data Process B Process E Variability/Uncertainty Can Not be Ignored Process A rocess C Process D Process C What does a predicted life of 101,601 cycles mean? 10 Cycles to Failure at 200 MPa Stress Range
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Notch Geometry predicted major contributor Tools Exist to Quantify Qy Variability & Sources 11
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Fatigue Lessons Learned • Total Life = Initiation + Propagation – Propagation Life 0 - >90% of Life 1,000,000 Cycle Test – Propagation Life 0 - 100% of 1,000 Cycle Test • “Same” Design - Different Supplier, Material, Processing ust Quantify & Manage Variability & Uncertainty Must Quantify & Manage Variability & Uncertainty – Variability Sources Include Loads/Sequence, Material Properties, Residual Stress,etc – Uncertainty Sources Include Loads, Material Properties, Sequence Effects, Residual Stress, Life Prediction Models • Knowing Uncertainty & Variability Enables More Efficient Use of Resources Must Look at Overall Fatigue Process 12
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EngineeringAspectsyofFatigueLifePredictionAug26 -...

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