Fatigue at High Temperature

Abstract

This report was prepared as the keynote address given at the 1972 Symposium on Fatigue at Elevated Temperatures at the University of Connecticut, 18–23 June, 1972. It describes the high-temperature fatigue problem as a failure process in a notch in some structure involving nucleation and early growth at the notch root, high-strain crack propagation through the plastic zone of the notch, and elastic crack growth to ultimate failure. Several of the important disciplines bearing on these three steps in the failure process are discussed. Particular attention is given to a description of the high-temperature phenomenology, distinctions between high- and low-cycle fatigue effects at high temperature, failure criteria including frequency and holdtime effects, the importance of the environment vis-a-vis creep in considering time effects on fatigue behavior, high-strain crack propagation, elastic crack growth, ratchetting effects, and methods for treating notches.