Plastic analysis of initially deformed thin-walled pressurized 30[formula omitted] to 180[formula omitted] pipe bends under in-plane opening bending moment

Abstract

The present study addresses outcomes of extensive nonlinear finite element analyses concerning a diverse geometric spectrum ranging from 30° to 180° pipe bend configurations accounting for the initial geometric deformations of the cross-sections resulting from the bending fabrication process. Pipe bends are modeled with the realistic and accurate cross-section by incorporating initial ovality and thinning/thickening (together called initial geometric imperfection) up to 20%. The modeled pipe bends are loaded by in-plane opening moment and internal pressure, considering material models of elastic-perfectly-plastic (EPP) and strain-hardening (SH). The detailed finite element results show that the presence of initial imperfection has a pronounced impact on the plastic collapse moment. At the lower magnitude of applied pressure, the initial imperfection decreases collapse moment of deformed pipe bends significantly as compared to that of circular cross-sectioned pipe bends. At the higher pressure values, the negative effect of initial imperfection decreases with increased pressure for thinner pipe bends. Based on the results of the conducted finite element analyses, governing empirical equations are formulated to predict the collapse moments of pressurized 30° to 180° thin-walled pipe bends with more realistic cross-section employing EPP and SH models.