Creep rapture of plastic pipes: Effect of eccentricity, residual stress, and circumferential orientation

Abstract

Plastic pipes made of high density polyethylene material with known geometric eccentricities and residual stresses were subjected to long term hydrostatic stress until rupture at different stresses and temperatures. Cooling and crystallisation rates of the pipe wall during the extrusion process were simulated along the production line. Crystallisation profile and circumferential orientation of polymer chains were measured at different angular locations and thicknesses around the circumference. It was shown that the plasticity-controlled rapture times of plastic pipes are significantly depended on geometric eccentricity as a result of re-distribution of residual stresses and circumferential orientation.