Definition of stress and strain ranges for multiaxial fatigue life evaluation under non-proportional loading

Abstract

A simple and clear method of evaluating stress and strain ranges under non-proportional multiaxial loading where principal directions of stress and strain are changed during a cycle is needed for assessing multiaxial fatigue. This paper proposes a simple method of determining the principal stress and strain ranges and the severity of non-prop ortional loading with defining the rotation angles of the maximum principal stress and strain in a three dimensional stress and strain space. Based on the method proposed, non-proportional stress and strain ranges are derived and applicability of the range to the life evaluation of type 304 stainless steel under 15 proportional and non-proportional strain paths are discussed. The strain range taking account of intensity of loading path reducing life can be suitable parameter for multiaxial fatigue life evaluation under non-proportional loading. © 2013 The Society of Materials Science, Japan.