Prediction Of Creep-rupture Failure Time Of HDPE Pipe

Currently, China is vigorously promoting the process of urbanization, and as one of the most widely used energy, the gas demand is growing rapidly. Because of the good corrosion resistance, superior mechanical properties, excellent welding performance and long service life, polyethylene (PE) pipe has been widely used for the transportion of gas in the cities. There are three typical failure modes of high density polyethylene (HDPE) pipe under hydrostatic pressure, which are relatively caused by creep, slow crack growth, and degradation. With the upgrade of the polyethylene raw materials and unexpected natural disasters occur frequently, the ductile failure as one of the biggest pitfalls in polyethylene gas pipe. Cohesive researches on prediction of creep-rupture failure time of HDPE Pipe is essential.Financial support from the National Key Technology R&D Program of "Twelfth Five-year Planning Program"(Project No.2011BAK06B01) and key project of national High Technology research and Development Program (Project No.2009AA044801), study mechanical properties of polyethylene pipe to propose ductile failure life prediction method, and the main conclusions are as follows:(1) Polyethylene pipe mechanical properties is studied. Take full account of the preparation of standard test sample, set of device parameters, temperature and other details on the polyethylene pipe specimen, constant strain rate tensile, creep test and relaxation test are accomplish. Through reasonable test treatment, the true stress-strain curve and the parameters of mechanical are obtained.(2) Polyethylene pipe constitutive model and validation of the model parameter. Choose a reasonable constitutive model to reflect the rate dependence of polyethylene pipe, the constitutive model parameters from a different strain rate data, through the relaxation test results to verify the rationality of the selected parameters and creep test results to reflect the choice of the constitutive predict the accuracy.(3) Prediction of Creep-rupture Failure Time of HDPE Pipe is proposed. Based on the basic assumptions. HDPE pipe creep under hydrostatic pressure before creep-rupture failure is predicted owed to the viscoelastic model. According to failure criteria, and the relationship between internal stress and failure time are obtained. and the result is compared with the literature data.