DEVELOPMENT OF FLAW CRITERIA FOR SHORT-TERM PERFORMANCE OF ELECTRO-FUSION PIPE WELDS

摘要

The effects of lack of fusion defects on short term performance of electro-fusion polyethylene gas pipe welds were evaluated when it is subjected to loadings that are experienced by the joint in service.Recently improved ultrasonic non-destructive evaluation techniques were developed for detecting some of these defects.However,it was necessary to develop criteria for determining the size and location of defects that would result in unacceptable short term performance of the weld.We performed a variety of short term tests on joints with pre-designed defects including tensile,crush,and pressure leak tests.In addition,finite element modeling was used to find the stress distribution for joints with and without defects.The experimental results were then used together with modeling work to propose criteria for the size and location of the defects.It was found that for short term performance,defects that are near the outside edge of the socket were most critical.