Evaluation of postulated cross sections with ovality and thinning for 90° pipe bends with circumferential throughwall cracks subjected to in-plane closing bending

A comparative study of postulated cross sections for failure analysis of 90°structurally deformed pipe bends with critical circumferential throughwall cracks was performed. Elliptical and semi-oval cross sections were assumed to determine the collapse loads under in-plane closing bending moment. Finite element analysis was conducted based on elastic-perfectly-plastic material considering geometric nonlinearity and twice-elastic-slope method was used to obtain collapse loads for each model. The influence of pipe ratio and bend radius in the presence of ovality and thinning were also investigated for the postulated cross sections. The results indicated a pronounced effect of ovality on collapse loads of throughwall circumferentially cracked pipe bends, primarily with elliptic cross sections whereas the thinning effect is significantly lower for both the cross sections. The present study provided a better estimation of the plastic loads and elliptic cross sections were found to be ideal in the analysis of cracked pipe bends for the present geometries and across the boundary conditions considered.