Study on Autofrettage for Medium-Thick Pressure Vessels

For medium-thick cylindrical pressure vessels, or the pressure vessels with radius ratio $k$ less than the value determined by the equation $k^2\ln k/\left(k^2-1\right)=1$, or $k\le 2.2184574899167\dots$, the theoretical problems on autofrettage are studied according to the third strength theory including the overstrain, the distributions of residual stresses and the total stresses, and load bearing by comprehensively controlling various stresses, such as residual stresses, the total stresses, and their equivalent stresses; the safe conditions of load bearing are found. The results show that for this kind of pressure vessel, the overstrain when they are treated with autofrettage can be 100%, with no compressive yield taking place. As long as the pressure that this kind of pressure vessel contains is not higher than the entire yield pressure $p_y/{\sigma }_y=\ln k$, the total stresses and their equivalent stress cannot exceed the yield strength ${\sigma }_y$, and the safety of the pressure vessels can be assured. The theory established in this research can be applied to engineering directly or with some minor modifications.