Stress Intensity Factor and Elastic Crack Opening Displacement Solutions of Complex Cracks in Pipe Using Elastic Finite Element Analyses

Abstract

In the present paper, the closedform expressions for the stress intensity factors (SIFs) and the elastic crack opening displacements (CODs) of complexcracked pipes are derived based on the systematic threedimensional (3D) elastic finiteelement (FE) analyses. The loading conditions that are evaluated include global bending moment, axial tension, and internal pressure. In terms of geometries, the geometric variables affecting the SIFs and the elastic CODs of complexcracked pipes, i.e., the crack angle of throughwall cracks (TWCs), the crack depth of fully circumferential, internal surface cracks in the inner surface of pipe, and the ratio of pipe mean radius to thickness, are systematically considered in the present FE analyses. The FE analysis procedure employed in the present study has been validated against the existing solutions for the circumferential TWC pipes. Using the present FE results, the shape factors of SIF and elastic COD for complexcracked pipes are tabulated as a function of geometric variables. The results are applied for closedform expressions of SIF and elastic COD when the pipe is subjected to simple loading conditions of bending, axial tension, or internal pressure. The proposed closedform expressions can estimate SIF and elastic COD of complexcracked pipes within maximum differences of 2.4% and 5.9% with FE results, respectively.