Influence Coefficients of Stress Intensity Factors for Curved Tubing With a Semi-Elliptical Crack

The boundary element method is employed to determine polynomial influence coefficients of stress intensity factors, K-I, for a semi-elliptical crack in internally pressurized thick-walled curved tubing. Numerical results of these coefficients are obtained for a wide range of geometric parameters; they are the bend radius ratio, cross-sectional radius ratio, angular extent of the bend, and relative crack depth. The use of influence coefficients allows K-I solutions to be determined for different load cases without repetitive 3D stress analysis of the cracked body. This is demonstrated for the case of autofrettage where the effects on K-I of the residual stresses arising from it are presented. [DOI: 10.1115/1.4006857]