On the overall accuracy of the Modified Wöhler Curve Method in estimating high-cycle multiaxial fatigue strength

Abstract

The aim of the present paper is to systematically investigate the accuracy of the so-called ModifiedW�hler Curve Method (MWCM) in estimating high-cycle fatigue strength of plain and notched engineeringmaterials damaged by in-service multiaxial load histories. In more detail, the MWCM, which is a bi-parametricalcritical plane approach, postulates that initiation and Stage I propagation of fatigue cracks occur on thosematerial planes experiencing the maximum shear stress amplitude (this being assumed to be always trueindependently from the degree of multiaxiality of the applied loading path). Further, the fatigue damage extentis hypothesised to depend also on the maximum stress perpendicular to the critical plane, the mean normalstress being corrected through the so-called mean stress sensitivity index (i.e., a material constant capable ofquantifying the sensitivity of the assessed material to the presence of superimposed static stresses). In thepresent investigation, the overall accuracy of the MWCM in estimating high-cycle fatigue strength was checkedthrough 704 endurance limits taken from the literature and generated, under multiaxial fatigue loading, bytesting both plain and notched samples made of 71 different materials. Such a massive validation exerciseallowed us to prove that the MWCM is highly accurate, resulting in 95% of the estimates falling within an errorinterval equal to �15%.