Evaluating the Residual Stress and Its Effect on the Quasi-Static Stress in Polyethylene Pipes

Abstract

Residual stress is generated during the production process. It can significantly affect the mechanical performance of pressurized polymer pipes. In this paper, six polyethylene (PE) pipes, including three high-density PEs (HDPE) and three medium-density PEs (MDPE) provided by different suppliers, were tested using a one-slit-ring method to measure the residual stress distribution along the hoop direction. Finite element (FE) simulation and mechanical testing were also employed in an iteration process to obtain the mechanical parameters of the six PE pipes. For the same PE pipe code from different suppliers, the results show that the magnitude of the residual hoop stress can be very different, resulting in different mechanical behaviors. In addition, the results are proposed to explain the scenario that was reported previously, i.e., the different critical quasi-static stress (the time-independent stress) levels of the PE pipes with the same pipe code. Since the quasi-static stress is expected to dominate the long-term behavior of the PE pipes, it is of great importance to carefully consider the effect of the residual stress on the determination of the quasi-static stress.

The Elasticity of Polymer Melts and Solutions in Shear and Extension Flows

“…It is quite evident that residual stresses and memory effects are associated with orientation depending on the stress in shear flow (see, e.g., Figure 25 in [ 42 ]) and related to its elasticity. One can find a description of frozen stresses, their direct observations, and the influence of this phenomenon on the performance of final products in numerous publications (e.g., [ 43 , 44 , 45 ]) and there is no doubt in its practical importance [ 46 ]. However, the general theoretical model of this phenomenon is absent although some attempts for stimulating calculations for frozen stresses are known [ 47 ].…”

Investigating the Deformation Characteristics of Buried High-Density Polyethylene Pipes: Considering the Effect of Sequentially Applying Pressure and Elevating Temperature

“…Underground conduits are used for a variety of purposes, including culverts, oil lines, coal slurry lines, subway tunnels, water mains, gas lines, telephone and electrical conduits, sewer lines, drain lines, water mains, gas lines, heat distribution lines, and telephone and electrical conduits [32,[36][37][38][39]. The properties of the soil envelope that surrounds a buried pipe system have a significant impact on the design of the buried pipe system.…”