The effect of specimen geometry on the low cycle fatigue life of metallic materials

Abstract

The effect of the specimen geometry on the measured fatigue life was investigated in this study. Low-cycle fatigue tests with hollow and solid specimens were performed and the differences in the two different specimen geometries were observed. A difference in the fatigue life between the hollow and solid specimens exists when the strain is large and diminishes as the strain decreases, which indicates that the difference stems from the crack propagation stage rather than the crack initiation stage. Two-dimensional finite element analysis was performed to quantify the effects of the specimen geometry in terms of the stress and strain near the crack tip. Larger internal plastic strain in the hollow specimen was found. This led to a higher plastic strain energy density and could explain the difference in the lifespan using the two specimen geometries.