Parameter Analysis for Temperature and Strain Rate Dependence of Low-Cycle Fatigue Life at High Temperatures

Abstract

A modified Larson-Miller parameter has been proposed to evaluate temperature and strain rate dependence on lowcycle fatigue life; it is written as P=T (logN₂₅-Alogε+B), where T is temperature, N₂₅ is fatigue life under symmetrical strain wave shapes, ε is strain rate, and A and B are constants. Material used in the analysis is SCMV 4 steel. The method is based on consideration of thermally activated processes causing temperature and strain rate dependence. It can give a threshold strain at fatigue limit, as Strohmeyer type equation is adopted to express a relationship between total strain range and fatigue life.