Fracture in Spherical Pressure Vessels

Abstract

The problem of fracture initiation and propagation from long flaws in spherical pressure vessels is considered from both theoretical and experimental viewpoints. Experimental work has been carried out on vessels of 5 ft diameter and 1/2 in thickness with a range of initial slit lengths from 3-24 in to determine the pressure for rupture by shear fracture. Geometrical variations were further examined by tests on two vessels of 26 in diameter and 1/2 in and 1/4 in thick respectively. The vessel tests were instrumented to give detailed behaviour local to the crack tip and to indicate the gross deformations occurring. The results have been analysed and found consistent with the theoretical view that fracture in vessels of ductile materials may be controlled by the occurrence of a limit mechanism. For less ductile materials it is suggested that fracture mechanics approaches should be used, with allowances for plasticity and bulging. The approach enables the prediction of critical crack lengths for unstable fracture in full size service vessels provided the relevant material properties are known.