Limit loads for 180° pipe bends under in-plane bending moment considering geometric nonlinearity

Abstract

This paper is dedicated to providing a detailed limit load analysis for 180° pipe bends under bending moment using three dimensional finite element (FE) method considering geometric nonlinearity. Results show that FE results for 180° pipe bends are all lower compared to those for 90° pipe bends, especially for pipe bends with thin wall and small bend radius (R/r = 1.5, r/t = 50). However, for pipe bends with thick wall and large bend radius (R/r = 4, r/t = 5), results seem very close. New predicted equations are proposed based on the FE results. If the geometric nonlinearity effect is considered, when the material parameters of yield strain εs = 0, results still obey the estimating solutions without geometric nonlinearity considered. But the geometry change should have some significant influence on the failure with the material's behavior changing. With the applied bending load increasing, the ovalization parameter C will also continue to increase. The change of the parameter C is significant for the thin pipe bends (r/t = 50), while is not obvious for thick pipe bends (r/t = 5). The influence of the bend radius on the parameter C is not significant. Geometric effect is significant for a high yield strain value that the pipes will have enough ability to be deformed.