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 autofrettage where a residual stress field is generated in the cylinder wall prior to use. An analytical autofrettage procedure of a thick-walled cylinder is proposed, with the aim of predicting the required autofrettage pressure for various levels of allowable pressure and hence achieving maximum fatigue life. A Finite Element Method (FEM) validation is 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 will 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 and maximum fatigue life are to be achieved. The analytical solutions compared satisfactorily to the numerical results where a very good correlation in form and magnitude was obtained.