Abstract
Interaction between normal and shear stresses plays an important role in multiaxial fatigue damage. The aim of this study was to investigate this interaction effect on fatigue behavior of shear failure mode materials under multiaxial loading conditions. In order to model the influence of normal stress on fatigue damage, the present study introduces a method based on the idea that the normal stress acting on the critical plane orientation causes two types of influence, first by affecting roughness induced closure, and second, by a fluctuating normal stress affecting the growth of small cracks in mode II. The summation of these terms could then be used in shear-based critical plane damage models, for example FS damage model, which use normal stress as a secondary input. In order to investigate the effect of the method, constant amplitude load paths with different levels of interaction between the normal and shear stresses were designed for an experimental program. The proposed method was observed to result in improved fatigue life estimations where significant interactions between normal and shear stresses exist.
Highlights
In materials with shear failure mode, cyclic shear strain on the failure plane is primarily controlling crack initiation, the normal stress acting on the failure plane can significantly affect the crack initiation process [1]
This study investigated the effect of interaction between normal and shear stresses on multiaxial fatigue behavior
A method was proposed to account for the interaction which could be used in shear-based critical plane damage models
Summary
In materials with shear failure mode, cyclic shear strain on the failure plane is primarily controlling crack initiation, the normal stress acting on the failure plane can significantly affect the crack initiation process [1]. Among different shear-based critical plane damage parameters, FS parameter [14], presented below, has been shown to successfully correlate test data under constant and variable amplitude multiaxial loads of different materials and components in many studies. This parameter was, selected for the implementation of the proposed method, given by:. A series of constant fatigue tests with irregular load paths consisting of different amounts of interactions between normal and shear stresses were designed The results of these tests were used to investigate the ability of the proposed method in taking the effect of interaction into account. The fatigue lives of these tests, as well as those found in the literature, were used to evaluate the effectiveness of the proposed method
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