A New Equivalent Thickness Model for Fracture Prediction on Round Rods with Elliptic Surface Cracks

Abstract

An equivalent thickness model is proposed to develop the fracture prediction method for round rods with elliptic surface cracks on the basis of a constraint equivalence principle and detailed three-dimensional (3D) stress field analysis near crack fronts with various elliptical shape factors t ([Formula: see text] 0.33, 0.4, 0.5, 0.67, 1) and crack depths a ([Formula: see text] 1/3, 2/3). The equivalent thickness is a function of crack depth a, elliptical shape factor t, elliptical parameter angle [Formula: see text] and radius of the round rod R. The reported fracture test data for the 20CrMo steel round rods with various elliptic surface cracks are adopted to validate the proposed equivalent thickness model. It is found that the improved 3D fracture prediction method by introducing the equivalent thickness is more effective than the traditional two-dimensional (2D) fracture prediction method. The prediction error is reduced from 10.5% to 3.1% for given round rods with elliptic surface cracks under tensile loading in this paper.