Dynamic Propagation of Circumferential Cracks in Two Pipes With Large-Scale Yielding

Abstract

The dynamic motions of circumferentially oriented, through cracks in two axially pre-stressed pipes were analyzed by a finite-difference shell code in the presence of large-scale yielding. Lacking any dynamic fracture criterion for large-scale yielding, a static ductile fracture criterion based on crack-tip opening angle (CTOA) was used. The results for a 6-in- (15.2-cm-) dia A533B steel and for an 18-in- (45.7-cm-) dia 316 stainless steel pipe subjected to axial loads showed that crack velocities were reduced to less than one half of the corresponding crack velocities of comparable brittle cracks. The onset of ductile crack propagation was delayed significantly in the larger 18-in- (45.7-cm-) dia 316 stainless steel pipe, thus indicating that this hold-off time is influenced by the inertia of the separating pipe segments. The importance of a realistic dynamic ductile fracture criterion is underscored.