Deformation and failure in polyethylene: correlation between mechanisms of creep and fatigue

Fatigue and creep tests have been conducted on medium density gas- and water-grade pipe materials using a longitudinally notched pipe geometry with internal pressurization. The failure in both types of test was brittle compared to the failure occurring when the unnotched pipe is exposed to a constant intense pressure. Further to this superficial similarity, fractographic studies revealed creep and fatigue failures to have many features in common. Thus it is perhaps not surprising that fatigue and creep lifetimes have been found to correlate well. The findings of this study give support to the concept of adopting fatigue as a quality control method in the production of plastic pipe.