Issue 43

F. Majid et alii, Frattura ed Integrità Strutturale, 43 (2018) 97-105; DOI: 10.3221/IGF-ESIS.43.07 103 of stage II and up to a life fraction β equal to 60%, the experimental damage is below the theoretical damage corresponding to γ = 1.9. Then it exceeds the curve of this loading level and overlaps in this time with the curve of the unified damage at a loading level γ = 2.55 at the end of stage II. In stage III curves of static damage and unified theory damage for γ = 1.9 return back similar. Both graphs of the two types of damage remain below the damage given by Miner. Figure 7 : Unified theory damage variation in function of the life fraction β. Figure 8 : Experimental, unified and Miner damages comparaison. C ONCLUSION he polypropylene random copolymer (PPR) is a thermoplastic material used for the transport of under pressure water, especially hot waters. In the industrial conditions, PPR pipes are exposed to severe conditions in terms of pressure and temperature. In order to characterize the behavior of the PPR at failure we have performed tests of overpressures at the laboratory scale according to ASTM D1599 standard, on virgin and notched pipes. According experimental and theoretical results. Many results have been found: • The notch had caused a drop of the ultimate pressure of the notched pipes compared to the undamaged ones. The increase in depth of the notch leads to a depletion of residual ultimate pressures of PPR notched pipes. • The calculation of the damage, by the experimental damage formulation, have led to determine the three stages of evolution of the damage initiation, progression and acceleration of damage. T