Crack tip opening angle during unstable ductile crack propagation of a high-pressure gas pipeline

A full gas burst test was conducted to clarify the CTOA history during ductile crack propagation in a high-pressure pipeline. The measurement results obtained by high-speed camera observation and image processing showed that the CTOA value remains constant during crack propagation despite the large changes in the crack velocity. The numerical results of a series of finite element analyses supported the intrinsic implications of the experimental results. Consequently, the validity of the constant CTOA criterion, which has the potential to improve the accuracy and efficiency of numerical simulations of unstable ductile crack propagation in a high-pressure pipeline, was verified.