抄録
The research of shear crack propagation with high velocity by spring-loaded DCB testing has a definite objective of obtaining the fracture criterion as well as the material resistance against fracture propagation, which is inseparably related to the establishment of design philosophy against unstable ductile fracture of highly pressurized gas pipelines.
The experiments and analyses were performed by DCB testing with several types of specimen geometry as well as with different spring compliances on wide variety of steels. It has been derived that the critical parameter, δc/t (crack opening displacement/material thickness), is a material resistance which is independent of specimen geometry (including curvature of groove), and of spring compliance.
It is also shown that the parameter, δc/t, is closely related to the fracture strain at the tip of running shear crack and that the criterion explains well the measured plastic zone width with a simple supplementary calculation. The comparison between the spring-loaded DCB testing with full-scale burst testing of pipelines has been done, using the available data, by estimating the plastic zone width in full-scale testing or by correlating the Jc value with Charpy energy in both testing. The effects of compliance in the springloaded DCB testing are also discussed.
