Stable growth and instability of circumferential crack in type 304 stainless steel pipes under tensile load

The fracture behaviors were studied with the experiment and the finite element analysis. 1) In the quasi-static low-compliance test, cracks extend stably throughout showing the flat fracture surfaces. The changes from stable to unstable crack extension, which is characterized by the 450 shear fracture surfaces, are observed in the 'quasi-static high-compliance' test as well as the 'dynamic-high-compliance' test. 2) Maximum crack velocity in the unstable fracture region exceeds 10 m/sec. 3) From the application and generation phase simulations by the finite element methods, it is found that the J-integral and the CTOA are effective parameters for the crack initiation and the stable crack extension. 4) Crack instability is predicted from the stationary conditions of the controlled displacement, taking the effect of the compliance in the loading system into account. (orig./HP)