Stress Intensity Factors for Axial Cracks in Pressurized Cylindrical Elements Using the Boundary Element Method

Pressure vessels and pipes are inspected to establish the presence of cracks that could affect their integrity for a reliable operation avoiding the possible negative impact of their failure. The Boundary Element Method (BEM) is a relatively new numerical method in this kind of applications, which is based on Integral Equations (IE), considering only the contour of the solid (meaning an easier meshing). The BEM has a good accuracy that promotes its use in stresses analysis. Crack growth modeling is one of the most important applications for the BEM, since it allows an accurate stress analysis in the crack faces and crack propagation analysis without re-meshing. This paper focuses on modeling an inside surface axial crack in a cylindrical element under internal pressure using 2D-BEM, to determine the mode I Stress Intensity Factors (KI) at the crack tip. These factors are used to predict the mechanical behavior of the element and its residual life when is subjected to cyclic loadings The BEM generates less conservative results than API 579 rules for Ri/t ≤ 10, meanwhile for Ri/t ≥ 12 the results are in a good agreement with that standard. New simple correlations to calculate KI for 5≤Ri/t≤10 and 10<Ri/t≤25, are offered.