Prediction of multiaxial fatigue life for complex three‐dimensional stress state considering effect of additional hardening

Abstract

In engineering practice, it is generally accepted that most of components are subjected to multiaxial stress‐strain state. To analyse this complicated loading state, different types of specimens of 2A12 (2124 in the United States) aluminium alloy were tested under multiaxial loading conditions and a new multiaxial fatigue analysis method for the state of three‐dimensional stress and strain is proposed. Elastic‐plastic finite element method (FEM) and a proposed vector computing method are used to describe the loading state at the critical point of specimen, by which the parameter ΓT is calculated at the new defined subcritical plane to consider the effect of additional cyclic hardening. Meanwhile, the principal equivalent strain is still calculated at the traditional critical plane. The new damage parameter is composed of different process parameters, by which the dynamic path of strain state, including loading environments and material properties, are fully considered in one loading cycle. According to experimental verifications with 2A12 aluminium alloy, the results show that the proposed method shows satisfactory, accurate, and reliable results for multiaxial fatigue life prediction in the state of three‐dimensional stress and strain.

Micromechanics-Based Low Cycle Fatigue Life Prediction Model of ECAPed Aluminum Alloy

“…However, for the ultrafine grains subjected to the local multiaxial strain-controlled loading history [28], the mean strain plays a non-negligible role in the evolution of small crack propagation as a result of complicated loading paths and nonproportional loading. Moreover, the local multiaxial stress-strain states at the grain level can give rise to the non-proportional cyclic additional hardening (NPACH) effect in the process of LCF loading [29,30]. As a result, the inhomogeneous plastic deformation is not only related to the stress state but also to the strain path.…”

A Novel Multiaxial Strain-Based Criterion Considering Additional Cyclic Hardening

“…It is worth noticing that a fatigue criterion cannot accurately estimate fatigue life by only considering the stress/strain state inside a material in terms of the computation of a suitable damage parameter. Among the criteria available in the literature for such an evaluation, both strain-and energy-based criteria are widely used [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17].…”