Fracture Mode Transition for Explosively Loaded GB/JB 20 Steel Containment Vessels

A rupture experiment was conducted on cylindrical explosion containment vessels (ECVs), where the fracture mode transition was observed. Microstructure examinations indicate the material GB/JB20 (AISI 1020) experienced a fibrous-to-cleavage fracture mechanism transition with increment of loading rate. Different from fracture mechanics method, a rate-dependent failure criterion is proposed to account for the dynamic fracture behavior, which is compatible with experimental observation that the material fails at low effective plastic strain when at high strain rates. A finite element analysis of a cylindrical containment vessel with different sizes of initial cracks was performed, where the overpressure caused by detonation was calculated, and the dynamic crack propagation and fracture mode transition were reproduced. In addition, a failure assessment including the estimation of limiting crack sizes corresponding to impulsive loading was conducted. It was found that a small variation of initial crack size has minor influence on the final fracture mode and profile, which is mainly dependent upon the intensity of impulsive load as well as the loading rate. The results also indicate that the crack propagates with strongly nonlinear speeding, most cracking length developed during the first structural vibration cycle.