DEVELOPMENT OF A RING TENSILE TEST FOR EVALUATING THE CHEMICAL COMPATIBILITY OF PLASTIC PIPES

摘要

A new test method for evaluating the resistance of plastic pipe to chemical attack and environmental stress cracking (ESC) has been developed. The fixture is a simple extension of the tensile creep rupture test method to ring samples excised from pipes. The design allows for immersion in a variety of aging substances at any temperature and stress level. Simple mechanics equations for curved beams can be used to select the proper load for matching the maximum tensile stress in the ring geometry to the hoop stress in pressurized pipe, and finite element analysis (FEA) was performed to validate the application of the calculations. The results of the analysis, as well as preliminary aging experiments, demonstrate that the geometry causes preferential cracking in the middle of the specimen, away from cut edges. This test method has the advantage of simulating the real application and the development of crazing and cracking and eventual failure more realistically than a displacement-controlled test. Limitations of the geometry are also discussed.