Low-Cycle Fatigue Life of Continuously Cyclic-Hardening Material

Abstract

A general fatigue life equation is derived by modifying the Tanaka-Mura-Wu dislocation pile-up model for variable strain-amplitude fatigue processes, where the fatigue crack nucleation life is expressed in terms of the root-mean-square of plastic strain range. Low-cycle fatigue tests were conducted on an austenitic stainless steel. At 400 °C and 600 °C, the material exhibits continuously cyclic-hardening behavior. The root-mean-square of plastic strain ranges is evaluated from the experimental data for each test condition at strain rates ranging from 0.0002/s to 0.02/s. The variable-amplitude Tanaka-Mura-Wu model is found to be in good agreement with the low-cycle fatigue (LCF) data, which effectively proves Miner's rule on the stored plastic strain energy basis.