Department of Mechanical Engineering, Chung-Ang University, Seoul 156-756, Korea
Principal researcher, Korea Gas Safety Corporation, Eumseong, Chungbuk 369-811, Korea
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 test results of an experimental tension test, burst test, three-point bend 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 defect could not increase the failure of the joints if the defect size was smaller than 15% of the pipe’s wall thickness regardless of the defect geometry, but the defect increased the failure even though the defect size was only 15% of the pipe’s wall thickness under the fatigue loading.