Lifetime Estimation Method of Polyethylene Pipe Based on the Full Notch Creep Test

The Creep Crack Growth (CCG) of polyethylene pipe directly limits its long-term lifetime. The long-term lifetime estimation of polyethylene pipe was proposed by combining the crack kinetics and Paris-Erdogan crack growth model. According the Full Notch Creep Test (FNCT) to measure the relationship between the crack opening displacement COD and the test time ti of the preformed PE ring notch specimens during creep tension, and the crack growth rate da/dt, stress intensity factor KI can be calculated, then the inherent parameters A, m of PE materials can be obtained through the Paris-Erdogan crack growth model. Finally, the relationship between the crack depth af and the crack growth time tCCG of polyethylene pipes in the long-term use process can be extrapolated. The test result shown that, when the specification of PE pipes were dn110-sdr11, if there was an initial crack with a depth of aini = 0.4mm on the outer wall of the pipe, and under the continuous action of pipe pressure with p = 0.4 MPa, when the depth crack of PE1 and PE2 pipes expanded to 0.8mm, it needed to maintain or replace the defective pipe section, and the lifetime of the pipes were 22.89 and 20.03 years. Respectively, if the pipes were not maintained and replaced in time, and it will exist medium leakage only takes 14.13 and 12.44 years.