Stress Waveform Effect on Low-Cycle Fatigue Life for SUS316FR Round Notched Bar and the Life Prediction

Abstract

This paper studies the stress waveform effect on low cycle fatigue life for three kinds of notched specimens at elevated temperature. Low cycle fatigue tests were carried out using circumferential notched specimens of SUS316FR stainless steel using fast-fast, slow-fast and hold-time stress waveforms at 923K. Neuber’s rule recommended in ASME Code Case was applied to estimate failure and crack initiation lives. Failure lives were underestimated by Neuber’s rule in ASME Code Case NH. Crack initiation lives under the fast-fast, slow-fast and hold-time stress waveforms were correlated within a factor of 4 scatter band by using modified Neuber’s equation in which the exponent of K t was changed from 2 to 1.2 in the combination with frequency modified fatigue life equation.