Effect of autofrettage on allowable pressure of thick-walled cylinders

Abstract

In optimal design of thick-walled cylinders, there are two main objectives to be achieved: increasing its strength-weight ratio and extending its fatigue life. This can be achieved by generating a residual stress field in the cylinder wall prior to use. In the present study, the objective is to present an analytical autofrettage procedure, with the aim of predicting the required autofrettage pressure for various levels of allowable pressure. The results could contribute to a better understanding of the role autofrettage plays in providing strength and performance in pressure vessels. A corresponding FEM validation will be provided. The results reveal three scenarios in the design of thick-walled cylinders. For maximum load carrying capacity, non-autofrettage is suitable when, in service, the whole wall thickness is intended to be yielded. Full autofrettage is suitable when, during subsequent operation, yielding is limited at the inner surface. Optimum autofrettage of the cylinder is suitable if a minimum equivalent stress is required.