LAUSR

Abstract The non-proportional hardening is revealed to be a main reason to influence the fatigue life of materials which are sustained to multiaxial low-cycle fatigue loading. Microstructurally speaking, increase of stacking faults to the grain size, formation of micro-twins in deformation bands and/or nucleation of martensite particles under non-proportional loading can introduce the strain hardening effect. Nevertheless to quantify the correlation between the microstructural phenomena and the macrostructural characteristic of material is not yet a trivial task. After quantitative analysis of the correlation between microstructural development and periodic deformation behaviour, an empirical non-linear hardening approach based on Benallal's NP factor estimation, which reflects the relationship between microstructural condition and internal stress responses is presented in this paper. Our approach is verified to be effective by experimental observations under different loading paths.