Effect of shape imperfections on elastic stresses of U-bends subjected to in-plane moment

Abstract

PurposePrecise assessment of elastic stress is required in the field of fracture mechanics. While bending a straight pipe, the deformation of the circular cross section out of roundness called ovality and thinning are foreseeable. The ovality has a significant effect on the structural integrity of the pipe. The sole objective of this paper is to provide new analytical solutions to predict accurate elastic stress distribution at the median section of the U-bend, with deformities such as ovality and thinning when subjected to in-plane closing moment by using elastic finite element analysis.Design/methodology/approachThe quarter model of the U bend has been analysed by using ABAQUS. The elastic stress components included in this analysis are longitudinal bending stress, longitudinal membrane stress, circumferential bending stress and circumferential membrane stress. Based on finite element results, analytical elastic stress solutions are also provided for both longitudinal and circumferential stresses by using these stress components.FindingsAs the ovality has a significant effect, it is further included in the analytical solution. The thinning is not included since it has very little effect. Analytical stress solutions are provided for a wide range of bend characteristics to include ovality, mean radius and thickness.Originality/valueSignificance of ovality and thinning on elastic stress of U-bend has not been reported in the existing literature.