Issue 43

F. Majid et alii, Frattura ed Integrità Strutturale, 43 (2018) 97-105; DOI: 10.3221/IGF-ESIS.43.07 97 Residual life prediction of defected Polypropylene Random copolymer pipes (PPR) Abderazzak Ouardi, Fatima Majid, Nadia Mouhib, Mohamed Elghorba University of Hassan II, National Superior School of Electricity and Mechanics Casablanca (ENSEM), LCCMMS, Morocco majidfatima9@gmail.com , http://orcid.org/0000-0001-8909-8232 A BSTRACT . The polypropylene random copolymer (PPR) is a thermoplastic material generally used for the transport of water under pressure, especially hot water. PPR pipes are exposed to severe conditions in terms of pressure and temperature, hence the need to characterize their fracture behavior in order to avoid the design risks. Sudden overpressure is one of the most common problems in piping. It can affect the security of goods and the safety of people. In this context, we have performed tests of overpressures at the laboratory scale according to ASTM D1599 standard, on virgin and notched pipes, to characterize mechanically the fracture behavior of PPR pipes. Afterwards, we identify experimentally the evolution of their damage. The calculation of the damage, by experimental damage models, have led to determine the three stages of evolution of the damage, which are the initiation, the progression and the acceleration of it. Therefore, the concept of reliability is used to specify the critical life fraction relative to the notch depth (βc) of a defect modeled as an external longitudinal groove on the PPR pipe. A comparison of PPR and HDPE pipes damage and reliability has been done. Moreover, a theoretical reassessment of the damage level was done through a judicious adaptation of the theoretical model proposed by the unified theory. From the latter, we proved that theoretical and experimental results show good agreement and correlations. K EYWORDS . Mechanical characterization; PPR themoplastic pipes; damage; reliability; burst pressure. Citation: Ouardi, A., Majid, F., Mouhib, N., Elghorba, M., Residual life prediction of defected Polypropylene Random copolymer pipes (PPR), Frattura ed Integrità Strutturale, 43 (2018) 97-105. Received: 16.10.2017 Accepted: 03.10.2017 Published: 01.01.2017 Copyright: © 2018 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION he polypropylene random copolymer (PPR) is a thermoplastic material made by copolymerizing propylene and small quantity of ethylene (usually less than 7 %). In fact, the role of ethylene co-monomer is to disrupt the crystallization of the main chain of propylene by introducing irregularities leading to a decrease of the crystallinity, rigidity, melting point and glass-transition temperature [1-2]. Thanks to their good physical, chemical and mechanical characteristics along with the low cost of the installation and maintenance, PPR pipes becomes quickly one of the most used polymers in the market. Their application merged from transport of hot and cold water, to system of air-conditioned, and various industrial and medical applications. A complete range of fittings that can be welded to create well tight systems, even under most severe conditions [3], improved PPR pipes system. T