Using a reverse life plot for estimating fatigue endurance/limit

Abstract

This short review paper describes the use of a reverse life plot, σ a versus 1/N f , for estimating a fatigue endurance/limit, σ FL. The method is applicable for different alloy-environment systems and load R-ratios. Due to inherent scatter in the fatigue data approaching fatigue limit, a ‘staircase’ method is often utilized that requires relatively large number of specimens (around 15–30) to be tested just for fatigue endurance/limit determination alone. The proposed method uses only high-cycle-fatigue (HCF) S-N data. The estimated fatigue endurance/limit is verified against the data from staircase method for 7000 Al alloy in air and corrosive 0.5 % NaCl solution environment. The comparison with the staircase method shows fairly good agreement. An additional example shows how this method estimates endurance limits for 4140 steels tested in three environments: dry air, air with 93 % RH, and aerated 3 % NaCl solution.