Influence of Hardening and Bauschinger Effect on Residual Stresses in Autofrettaged Cylindrical Vessel

The paper deals with the combined influence of the hardening and the Bauschinger effect on the residual stress distribution in autofrettaged close-ended cylindrical vessels. Stress fields are determined numerically by solving the differential equations with the Runge-Kutta method, taking into account the variability of the Bauschinger effect as a function of pre-strains, as well as the hardening of the material during the loading phase. The approach is more general than that considered by Chen's model, where the material behaviour is elastic-perfectly plastic during the loading and the Bauschinger effect is constant during unloading. A parametric analysis shows that residual stresses are very sensitive to changes of the Bauschinger effect and to the plastic tangent modulus, resulting in a more or less pronounced decrease of the hoop stresses at the cylinder bore radius, with respect to the experimented ones by using simplified methods.