A study on residual stress mitigation of the HDPE pipe for various annealing conditions

Abstract

This paper presents effects of the annealing condition variables such as temperature and time on the residual stress mitigation. The effects were investigated by using the various measurement methods such as hole-drilling method and slitting method. As a result of the investigation, the residual stress mitigation magnitude increases with increasing the annealing time and temperature. Based on the investigation results, the quantitative correlations between the annealing variables and the residual stress mitigation were derived. Finally, the effect of long-term operation under the normal operating temperature conditions on the residual stress mitigation was investigated by referring to the derived equations and performing some additional tests, and it is identified that the residual stresses are not significantly relaxed over the design lifetime of the safety class III buried HDPE pipes.