Session: MF-13-01 Composite and Non-Metallic Systems for Pressure Vessels and Piping

Paper Number: 106404

106404 - Assessing Residual Stresses in Pe-Rt Pipes and Annealing Temperature Sensitivity Analysis 

Pipe made from polyethylene with raised temperature (PE-RT) service capability offers several advantages in terms of material performance, and has broad application in the industry. However, residual stresses are typically present in PE-RT pipe after fabrication, which may affect pipe strength under service conditions. Research on this phenomenon in PE-RT pipe is limited, and hence, the present study investigated the residual stresses and means for mitigating them through annealing at elevated temperatures. Residual tensile and compressive stresses are formed on the inner and outer portions of extruded pipes, respectively, due to the rapid cooling that is typically applied on the outside of the pipes after the extrusion process. The objective of the present work was to assess experimentally residual stresses in PE-RT pipes. In addition, using the experimental methods, a sensitivity study on the annealing temperature for mitigating residual stresses was performed. The experimental procedures were adopted from the ASTM E1928-13 standard. In compliance with this standard, the PE-RT pipes under investigation can be considered as thin-walled tubes for analysis purposes. Moreover, the creep behavior of plastics was incorporated in the final calculation of residual stress values. Two types of slitting methods were applied to assess the residual stresses: (i) To determine the residual hoop stress, a 45 degree section was cut from ring samples, and then the change in ring diameter was observed; (ii) for the longitudinal residual stress, a tongue-like section was cut lengthwise into pipe samples, and the deformation of these sections was observed. For all cutting purposes, coolant was used to avoid any heating effects. The sample lengths varied from 0.2 to 3.0 times the outer pipe diameter. In this manner, effects of specimen length on the test results were ascertained. Experiments conducted for non-annealed PE-RT pipe, as well as pipe annealed at 90 degree Celsius, revealed the presence of substantial residual stresses. Using the developed procedures the study seeks to identify the annealing temperature that yields the lowest possible residual stresses in the PE-RT pipes. Present work includes a discussion on whether the ratio of ideal annealing temperature to melting point can extrapolated as a key parameter from PE-RT to other thermoplastic polymer materials.

Presenting Author: Arun Biradar University of Alberta

Presenting Author Biography: Arun Biradar, first year PhD student at University of Alberta, Edmonton, Alberta, CANADA
Major: Mechanical Engineering
Research concentration: Durability and Thermomechanical Performance Evaluation of Thermoplastic Composites

Current and Previous Education Details are as below:

University of Alberta, Edmonton, AB Starting
Started this year on Jan 4th, 2022
Doctor of Philosophy (PhD) in Mechanical Engineering

Florida Institute of Technology, Melbourne, FL, USA
Graduated on Dec 15th, 2018
Master of Science in Mechanical Engineering
GPA 3.90

B.V. Bhoomaraddi College of Engineering & Technology, India
Graduated in June 2015
Bachelor of Engineering in Mechanical Engineering
GPA 3.96

Authors:

Arun Biradar University of Alberta
Jorge Palacios Moreno University of Alberta
Pierre Mertiny University of Alberta