Residual stress analysis in a polyethylene pipe wall

Abstract

Residual stresses are tensions that remain in the material even when it is no longer subjected to external pressures. The most prevalent causes of residual stresses include fabrication operations, thermal processing, welding, heat treatment, mechanical shaping, and extrusion. In this study, an experimental method is used to determine the residual stresses in a 125 mm diameter polyethylene tube meant for natural gas transportation. The material removal process in sequential machining is used to extract five successive layers from the tube's wall. In fact, by successively removing layers, the variation in curvature makes it possible to evaluate the stresses that were present in the removed part. It is then theoretically possible to go back to the distribution of stresses in the thickness and to determine the profile of residual stresses. It was found that compressive stresses are relieved in the exterior of the wall. And other positive tensile stresses are released inside the wall. This configuration is related to the manufacturing process, namely extrusion.