Fatigue Life Calculator
Estimate fatigue life in cycles using the S-N approach with modified endurance limit. Accounts for surface finish and size effects.
Inputs
psi
psi
psi
Results
Cycles to Failure
1
Fatigue Life (@ 1000 RPM)
0 hrs
Modified Endurance Limit17,000 psi
Fatigue Safety Factor0.57
How to Use This Calculator
- Enter the Stress Amplitude (Ο_a) in psi at the critical location β for fully reversed loading this is half the stress range.
- Enter the Endurance Limit (Se') in psi: for steel, Se' β 0.5 Γ Sut up to about 100 ksi.
- Enter the Ultimate Tensile Strength (Sut) in psi from the material datasheet.
- Set the Surface Factor (ka) based on surface finish: ground β 0.90, machined β 0.75, hot-rolled β 0.60.
- Set the Size Factor (kb): 1.0 for d < 0.3", 0.85 for d = 0.3β2", 0.70β0.80 for d = 2β10".
- Review Cycles to Failure and the Fatigue Safety Factor β a factor below 1.0 indicates infinite-life is not achieved at the applied stress.
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