Understand that repeated loading below a material's static strength can still cause failure over many cycles (fatigue), that life drops steeply as stress amplitude rises, and that below the endurance limit, some materials can withstand cyclic loading indefinitely.
x-axis: stress amplitude (MPa) · y-axis: log₁₀(cycles to failure), capped at 8 for runouts
Fatigue Life
179 cyclesBasquin's relation: S = Sf'·(2N)^bCycles to failure: N = 0.5·(S / Sf')^(1/b)Below the endurance limit (Se): life is treated as infiniteKeep the default stress amplitude of 500 MPa. Confirm the fatigue life is finite and under 1,000 cycles.
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