Double cracks with single-inclusion fatigue propagation of surface-quenched large modulus rack

Abstract

A connectivity criterion based on the analysis of the stress intensity factor for the double cracks and inclusion was developed to study the residual life of large modulus crack. Applying the moving load, the finite element model in FRANC3D was proposed to study the variation law of the spacing ratio [Formula: see text] and stress intensity factor amplification coefficient [Formula: see text]. Also, the spacing ratio threshold and the initial spacing threshold for the law of propagation of the double cracks and inclusion were obtained. After the analysis of the threshold, the initial equivalent single crack [Formula: see text] was obtained based on the function [Formula: see text] and stress intensity factor for circular mode I crack [Formula: see text]. The final equivalent single crack [Formula: see text] was obtained by innovative use of the fatigue load cycle correction coefficient [Formula: see text]. Moreover, the residual fatigue life of surface-quenched large modulus rack is analyzed to be 55 years. It is revealed that the design of the large modulus crack is safe for the normal operation of the Three Gorges Shiplift.