Work out fatigue life instantly with clear inputs, formula shown and shareable results.
In the high cycle regime the S-N curve is a straight line on log-log axes, so life scales as (Se / Sa)^(1/b) about the 10⁶ cycle endurance point. With a typical exponent near 0.1 the sensitivity is extreme: a 25 percent stress increase can cut life by an order of magnitude.
Power law S-N
N = 10^6 x (Se / Sa)^(1/b)
Preliminary estimate only. Fatigue assessment must be carried out by a qualified engineer using material-specific S-N data, mean stress correction, surface and size factors and stress concentration effects.
N = 10^6 x (Se / Sa)^(1/b). In the high cycle regime the S-N curve is a straight line on log-log axes, so life scales as (Se / Sa)^(1/b) about the 10⁶ cycle endurance point.
Traditionally yes for carbon steels, but modern very-high-cycle data show failures beyond 10⁸ cycles from internal defects, and aluminium has no true endurance limit at all.
This calculator takes 3 inputs: Applied stress amplitude, Endurance strength at 10⁶ cycles, S-N curve exponent b. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.