Fatigue Life Estimator (Basquin)
Cycles to failure from stress amplitude via the high-cycle power law.
The brutal arithmetic of fatigue: 10% more stress โ 3ร shorter life at b = โ0.085. Below the endurance limit (steels only) life becomes 'infinite' โ aluminium never gets that mercy.
Formula
Note: Smooth-specimen estimate โ apply surface, size and notch (K_f) corrections for real parts.
Fatigue Life Estimator (Basquin) is a free fatigue life for design engineers, metallurgists and QA inspectors โ instant, accurate and 100% client-side, with the governing formula and reference shown next to the result so the number can be defended, not just quoted.
About Fatigue Life Estimator (Basquin)
Cycles to failure from stress amplitude via the high-cycle power law. The calculation implements ฯ_a = ฯ'_fยท(2N)^b โ N = ยฝ(ฯ_a/ฯ'_f)^(1/b) (Basquin (1910); Shigley ch. 6). The brutal arithmetic of fatigue: 10% more stress โ 3ร shorter life at b = โ0.085. Below the endurance limit (steels only) life becomes 'infinite' โ aluminium never gets that mercy.
How to use Fatigue Life Estimator (Basquin)
- 1Enter Stress amplitude in MPa.
- 2Enter Fatigue strength coeff ฯ'_f in MPa (โ UTS + 345 MPa for steels).
- 3Enter Basquin exponent b (Steels โ0.05 to โ0.12).
- 4Read Cycles to failure (2N reversals) instantly โ no submit button needed.
- 5Need US units? Flip the SI/Imperial toggle and every field converts.
Why use Fatigue Life Estimator (Basquin)?
- โImplements the standard formula โ ฯ_a = ฯ'_fยท(2N)^b โ N = ยฝ(ฯ_a/ฯ'_f)^(1/b)
- โReference cited on-page: Basquin (1910); Shigley ch. 6
- โOne-click SI โ Imperial toggle โ values convert in place, physics stays in SI
- โLive worked example: the substitution recomputes from your numbers
- โRuns entirely in your browser โ nothing uploaded, free forever
Frequently asked questions
What formula does the Fatigue Life Estimator (Basquin) use?+
It computes ฯ_a = ฯ'_fยท(2N)^b โ N = ยฝ(ฯ_a/ฯ'_f)^(1/b), per Basquin (1910); Shigley ch. 6. The formula is displayed under the result along with a worked example substituted with your own inputs.
What should I keep in mind when using this calculator?+
The brutal arithmetic of fatigue: 10% more stress โ 3ร shorter life at b = โ0.085. Below the endurance limit (steels only) life becomes 'infinite' โ aluminium never gets that mercy. Note: Smooth-specimen estimate โ apply surface, size and notch (K_f) corrections for real parts.
Where do the material property defaults come from?+
Defaults are standard handbook values (ASM, manufacturer datasheets, the cited standard). Always substitute certified values from your material's test certificate for critical work.
Is the Fatigue Life Estimator (Basquin) free to use?+
Yes โ completely free, no sign-up, no limits. It runs client-side in your browser, so inputs stay private and results are instant even on slow connections.
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