Failure of models of thin-walled shells when loaded by internal pressure

Abstract

1. In the presence of longitudinal cracks of varied length (40–160 mm) and varied amount of elastic energy of the compressed air model (1400–9400 kgf·m) the failure of models on thin-walled shells 0.5 mm thick, when loaded by an internal pressure, has a ductile character, independently of the fitting of transverse tires located at different distances from the crack tip (from 20 to 105 mm). 2. As the initial length of crack increases, its subcritical growth in thin-walled shells increases linearly. 3. As the crack length increases, the failure stress (gross) is substantially reduced (from 22 to 9 kgf/mm2). At the same time the character of failure is altered: a straight-line propagation of the crack along the generator of the cylinder is replaced by a curvilinear propagation that approximates the failure direction to the circumferential direction. 4. With a reduction by a factor of two the amount of elastic energy contained by the compressed air model has almost no effect on the strength and geometrical features of the fracture. A dominant effect on the character of fracture is exerted, apparently, by the magnitude of the failure pressure which alters the relationship of the velocities of propagation of the crack and the waves of elastic unloading. 5. The limitations on the applicability of the existing calculation methods of the fracture mechanics, for the estimation of the resistance to a ductile failure of thin-walled cylindrical shells, is revealed, and appropriate corrections are proposed. 6. The effectiveness of the use of transverse tires to stop a started ductile failure of shells loaded by an internal pressure, depends on the distance between the tire and the vertex of the initial crack. This distance leads to a transition from the stoppage of the moving crack to its direction being altered.