Profiled HDPE Pipe Response to Parallel Plate Loading

The parallel plate load test is used to measure ‘pipe stiffness’ for HDPE pipe. Pipe stiffness is employed as a measure of pipe resistance to bending deformation as well as a quality control index for the manufacturing process. Unfortunately, the parallel plate test induces a complex state of stress and strain in the pipe, and interpretation of the test results is not straightforward. Simple analysis for a thin circular ring or shell is generally used for these products, but in reality materials like high density polyethylene are viscoelastic (modulus is time and load path dependent) and the depth of the pipe profile may be a significant proportion of the diameter. This paper introduces a three dimensional viscoelastic finite element analysis for HDPE pipe, testing the computational method through comparisons with laboratory data. The analysis is used to examine the nature of pipe response during the parallel plate test. The local distributions of stress and strain through the profile are considered, as well as the effect of loading rate on the pipe response. Conclusions are drawn regarding the ability of conventional thin ring theory to predict circumferential stress and strain, and the implications for pipe design are briefly discussed.