Comparative study of axial and circumferential defects severity on the failure of polypropylene (PPR) pipes

Abstract The aim of the present work is to analyze the harmfulness of the defect, through a comparative study of the criticality of axial defects comparing to circumferential ones on Polypropylene random copolymer (PPR) pipes, and to be able to predict the residual life of defected pipes. In this context, burst tests were carried out on virgin PPR pipes and pre-damaged ones. Adaptation of the static damage model of the unified theory, initially developed in fatigue, for short term burst test allowed to define the three stages of development of the damage and thus to determine the critical life fraction (βc) from which, these defects become dangerous. In addition, the concept of the reliability is used to specify the depths corresponding to 50% of reliability for both axial and circumferential defects. Results obtained proved that axial defects are more dangerous than circumferential ones.