An investigation of time-dependent behavior of medium density polyethylene pipes

Das, Suprio (2021) An investigation of time-dependent behavior of medium density polyethylene pipes. Masters thesis, Memorial University of Newfoundland.

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Abstract

Medium density polyethylene (MDPE) pipes are extensively used for gas distribution system in Canada and worldwide. MDPE pipe material possesses time-dependent mechanical properties that governs the performance of the pipes in service. In this research, laboratory investigation is carried out to investigate the time-dependent behavior of a MDPE pipe material. Uniaxial tensile tests were conducted with samples (coupons) cut from the wall of a 60-mm diameter MDPE pipe. A tensile test with a sample of full cross-section of the pipe is also conducted to investigate the influence of sample type on the test results. The test program includes uniaxial testings at various strain rates to capture the effects of loading rates, creep testing and relaxation testing. The experimental results are used to develop a numerical approach for modeling the time-dependent behavior using a commercially available finite element software, Abaqus. The strain-rate dependent material behavior of MDPE is incorporated in Abaqus through development of a user subroutine. The proposed modeling approach is found to successfully simulate the uniaxial test results. Applicability of the proposed modeling framework is demonstrated through investigating the time-dependent behavior of conventional buried MDPE pipe subjected to surface load and a pipeline subjected to rate-dependent lateral ground movement.

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