Nonproportional low cycle fatigue lives of type 304 stainless steel and 6061 al alloy under 14 loading paths at room temperature

摘要

This paper studies the effect of nonproportional straining on tension-torsion low cycle fatigue lives of two types of materials. Extensive low cycle fatigue tests under 14 proportional and nonproportional strain paths were carried out using Type 304 stainless and 6061 aluminum hollow cylinder specimens at room temperature, to draw influential factors on low cycle fatigue lives. Nonproportional straining significantly reduced fatigue lives depending on strain history and material. Nonproportional strains proposed in this paper, △ε{sub}(NP) and (△ε{sup}*){sub}(NP) successfully correlated nonproportional low cycle fatigue lives for the two materials. However, ASME strain, defined in Code Case N-47, gave a significantly unconservative prediction.