Effect of multiaxial stress on low cycle fatigue

Abstract

This paper overviews state of the art of multiaxial low cycle fatigue. Many review papers have already published on multiaxial low cycle fatigue and most of the review papers discuss correlation parameters of multiaxial low cycle fatigue lives by categorizing the parameters. This paper, however, rather focuses on the physical background of the effect of multiaxial stresses and strains on low cycle fatigue lives. Firstly, little effect of mean stress (hydrostatic stress) on tensile stress-strain relationships was presented to discuss little effect of the mean stress on crack initiation lives in multiaxial low cycle fatigue. Next, competing two cracking modes, maximum shear and principal cracking modes are discussed. The two cracking modes complexly occurred in multiaxial low cycle fatigue, depending on strain range, strain multiaxiality and existence of notches. At the third part of this paper, couples of energy and strain parameters developed by the authors were introduced and discussed for the correlation of multiaxial low cycle fatigue lives, and those parameters were compared to examine the difference of the parameters. Nonproportional low cycle fatigue lives were discussed in relation with the additional hardening of materials at the last of the paper.