Multiaxial fatigue life predictions of additively manufactured metals using a hybrid of linear elastic fracture mechanics and a critical plane approach

Abstract

This paper introduces a hybrid approach which leverages Fatemi-Socie critical plane analysis to determine an equivalent-damage uniaxial stress amplitude for various multiaxial loading conditions including uniaxial, torsion, and axial-torsion. Then, mode I crack growth constants along with initial defect information are used to make life predictions for multiaxial loadings as a function of their equivalent-damage uniaxial stress amplitudes. Two different Laser-Powder Bed Fusion metals, Ti-6Al-4V and 17-4 PH stainless steel, in a total of nine different surface and heat treatment conditions are analyzed and life predictions based on initial defect size and mode I crack growth properties from the literature are made using the Hartman-Schijve crack growth equation.