S-N Curve Fatigue Analysis
Se' (base endurance limit) = 0.5 x UTS (for steel, UTS < 1400 MPa)
Se (modified) = Se' x ka x kb x kc x kd x ke
Goodman correction: Sa_corr = Sa / (1 - Sm/UTS)
The endurance limit is modified by surface finish (ka), size (kb), reliability (ke), and other factors. For aluminum, there is no true endurance limit; fatigue life is typically evaluated at 5x10^8 cycles.