New research findings on non-proportional low cycle fatigue

Abstract

One of the challenges regarding multiaxial fatigue damage predictions is non-proportional loading. Relevant studies have shown that these multiaxial loadings cause significant additional hardening and reduction in durability due to non-proportionality. Fatigue life predictions due to non-proportional loadings are based on an equivalent nonproportional strain range that considers a material constant related to additional hardening and a non-proportionality factor. In this paper an analysis of the non-proportional factor for three multiaxial loadings forming a square in γ/√3 -ε coordinates is carried out. One of the observations revealed by this analysis is the sensitivity of the non-proportional factor to variable shear strain rate.1