Endurance Limit Estimator
First-pass S_e for steel from UTS, with the Marin correction factors listed.
The polished lab specimen lives a fantasy life — real surfaces, sizes and loads halve it. Above S_ut ≈ 1,400 MPa the limit stops rising: inclusions take over as crack starters.
Formula
Endurance Limit Estimator is a free endurance limit for design engineers, metallurgists and QA inspectors — 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 Endurance Limit Estimator
First-pass S_e for steel from UTS, with the Marin correction factors listed. The calculation implements S_e′ = 0.5·S_ut (≤700 MPa); S_e = k_a·k_b·k_c·…·S_e′ (Marin factors — Shigley ch. 6). The polished lab specimen lives a fantasy life — real surfaces, sizes and loads halve it. Above S_ut ≈ 1,400 MPa the limit stops rising: inclusions take over as crack starters.
How to use Endurance Limit Estimator
- 1Enter Ultimate tensile strength in MPa.
- 2Enter Surface factor k_a (Ground 0.9 · machined 0.7–0.8 · hot-rolled 0.5 · forged 0.4).
- 3Enter Other factors (size×load×temp).
- 4Read Lab specimen S_e′, Corrected part S_e instantly — no submit button needed.
- 5Need US units? Flip the SI/Imperial toggle and every field converts.
Why use Endurance Limit Estimator?
- ✓Implements the standard formula — S_e′ = 0.5·S_ut (≤700 MPa); S_e = k_a·k_b·k_c·…·S_e′
- ✓Reference cited on-page: Marin factors — Shigley ch. 6
- ✓One-click SI ⇄ Imperial toggle — values convert in place, physics stays in SI
- ✓Runs entirely in your browser — nothing uploaded, free forever
Frequently asked questions
What formula does the Endurance Limit Estimator use?+
It computes S_e′ = 0.5·S_ut (≤700 MPa); S_e = k_a·k_b·k_c·…·S_e′, per Marin factors — Shigley ch. 6. The formula is displayed under the result.
What should I keep in mind when using this calculator?+
The polished lab specimen lives a fantasy life — real surfaces, sizes and loads halve it. Above S_ut ≈ 1,400 MPa the limit stops rising: inclusions take over as crack starters.
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 Endurance Limit Estimator free to use?+
Yes — 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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