Stress Ratio & Amplitude Calculator
R-ratio, amplitude and mean from the max/min stress of a fatigue cycle.
R = โ1 is fully reversed (rotating shaft), R = 0 pulsating, R โ 1 nearly static. Every S-N curve is valid at ONE R only โ check before you borrow data.
Formula
Stress Ratio & Amplitude Calculator is a free stress ratio R 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 Stress Ratio & Amplitude Calculator
R-ratio, amplitude and mean from the max/min stress of a fatigue cycle. The calculation implements R = ฯ_min/ฯ_max; ฯ_a = (ฯ_maxโฯ_min)/2 (Fatigue testing conventions โ ASTM E466). R = โ1 is fully reversed (rotating shaft), R = 0 pulsating, R โ 1 nearly static. Every S-N curve is valid at ONE R only โ check before you borrow data.
How to use Stress Ratio & Amplitude Calculator
- 1Enter Maximum stress in MPa.
- 2Enter Minimum stress in MPa.
- 3Read Stress ratio R, Amplitude ฯ_a, Mean ฯ_m instantly โ no submit button needed.
- 4Need US units? Flip the SI/Imperial toggle and every field converts.
Why use Stress Ratio & Amplitude Calculator?
- โImplements the standard formula โ R = ฯ_min/ฯ_max; ฯ_a = (ฯ_maxโฯ_min)/2
- โReference cited on-page: Fatigue testing conventions โ ASTM E466
- 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 Stress Ratio & Amplitude Calculator use?+
It computes R = ฯ_min/ฯ_max; ฯ_a = (ฯ_maxโฯ_min)/2, per Fatigue testing conventions โ ASTM E466. 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?+
R = โ1 is fully reversed (rotating shaft), R = 0 pulsating, R โ 1 nearly static. Every S-N curve is valid at ONE R only โ check before you borrow data.
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 Stress Ratio & Amplitude Calculator 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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