Linear viscoelastic modelling of profiled high density polyethylene pipe

Abstract

Rheological model parameters for a linear viscoelastic finite element analysis are developed for corrugated polyethylene pipes. Relaxation test data from parallel plate load tests on lined corrugated high density polyethylene pipes are used, for pipes deflected to 5% and 10% vertical diameter decrease. Three-dimensional time-dependent finite element analysis is then used to estimate the time-dependent response of a 610 mm diameter pipe subjected to a constant rate of vertical diameter decrease with time. Predictions are obtained for deflection rates varying over three orders of magnitude, for direct comparison with laboratory test results. Small deflection (5%) relaxation rheology leads to good predictions of measured response up to 3% vertical pipe deflection. Large deflection (10%) rheology yields reasonable predictions for pipe response between 3% and 10% vertical deflection. Levels of strain are examined in the pipe profile, and a peak local tensile strain of 0.6% is estimated for the pipe deflected to 3% vertical diameter decrease. The rheological models should permit prediction of response under parallel plate loading for other pipe profiles. These models might also be used for estimation of pipe response under other loading conditions (such as deep burial in the field).