Stress characterization of autofrettaged thick-walled cylinders

Abstract

The inaccessibility of commercial software has necessitated the development of low-cost, general-purpose finite element method (FEM) computer programs for structural analysis. Using the FEM program, the elastic, elastic-plastic, residual and service stresses and displacements in a closed ended, thick-walled cylinder under internal pressure were established. The displacement formulation was implemented and eight-noded brick isoparametric elements chosen. The frontal solution technique and the incremental theory of plasticity were used, as only limited computing facilities were available. The results were found to be in very good agreement with the through-thickness analytical values. The benefits of autofrettage were demonstrated and an optimum overstrain of 16% established for a cylinder with a thickness ratio of 2. The material economy achieved through autofrettage and the limitations imposed are illustrated. The FEM program could therefore be reliably used for other complex geometries and load conditions.