Theory for Accelerated Slow Crack Propagation in Polyethylene Fuel Pipes. Annual Report 1987-1988

摘要

The report describes a test for assessing the resistance of polyethylene fuel gas pipe materials to brittle crack propagation. The test employs fatigue loading to a notched specimen. Pipe specimens prepared from 2306-IIC and 2306-IA exhibit an initial stage of brittle crack propagation which becomes progressively ductile as it approaches ultimate failure by tearing. The complete test duration is extremely short in comparison to others currently employed, yet it similarly ranks both materials tested. Further, crack layer analysis is employed to evaluate the specific energy of fracture, gamma, a fundamental parameter characteristic of the material's resistance to brittle crack propagation. It is also found from microscopic examinations that brittle fatigue involves a crazing mechanism known to occur under creep condition.