A semi-empirical model for structural integrity assessment of defected high density polyethylene pipes

Abstract

The main objective of this study was to propose semi-empirical models to facilitate the integrity analyze of a defective high density polyethylene (HDPE) pipe. To this end, an experimental compact tension test(CT) was performed to establish the HDPE's crack extension resistance (J-R) curve. This curve was used to determine the fracture toughness JIC-CT. different existing approaches in the literature were considered showing how the gap between JIC values is considerable. In order to designate the adequate value of toughness, a numerical analysis is performed and validated with the experimental test. The developed FE model gives the evolution of the J-integral as well as the distribution of the opening stress in the vicinity of the defect. By analyzing these two results we were able to define the fracture toughness JIC-CT and the ultimate pressure of pipe leading to the crack initiation.In the second part, basing on the J-integral concept, the harmfulness of surface semi-elliptical crack located at PE100 pipe wall under internal pressure has been studied using Abaqus software. The crack and pipe size effect on the fracture toughness has been discussed. Results of the finite element analysis has been used to adjust a semi-empirical model which was developed to determine J-integral variation with pipe internal pressure. In like manner, an approximate formula of PE100 pipe fracture toughness as function of pipe size and JIC-CT has been proposed. This allowed us to define the ultimate pressure of pipe leading to the crack initiation.