Effects of defects on failure of butt fusion welded polyethylene pipe

Medium density polyethylene (MDPE) pipes are usually welded together by butt fusion welding. The quality of butt fusion welded MDPE pipe joints is seriously affected by welding defects sometimes. This paper presented the results of tension test, burst test, three-point bending test, crush test, and fatigue test to show the effect of a single welding defect on the failure of butt fusion welded MDPE pipe joints. The fracture resistance of the joints without welding defects was studied by a fracture test too. The results showed that under the tension, pressure, bend, and crush loadings, the failure of the joints was not affected by the single welding defect if the defect size was smaller than 15% of the pipe's wall thickness regardless of the defect geometry, but the defect accelerated the failure even though the defect size was only 15% of the pipe's wall thickness under the fatigue loading.