Residual stress analyses of re-autofrettaged thick-walled tubes

In this paper the effect of the re-autofrettage process on the residual stress distribution at the wall of a thick-walled tube is considered. For accurate material behavior modeling, it is assumed that the yield surface is a function of all the stress invariants. Also for estimating the behavior of the material under loading–unloading process, a modified Chaboche's hardening model is applied.For evaluation of this unloading behavior model a series of loading–unloading tests are conducted on specimens that are made of the high strength steel, DIN1.6959. In addition the finite element simulations are implemented to simulate the re-autofrettage process and to estimate the residual stresses. The numerical results show that the re-autofrettage process without heat treatment only improves the residual stress distribution in high autofrettage percentage and for low autofrettage percentage this method is not beneficial. However, the re-autofrettage process with ‘‘heat soak’’ treatment generally improves the residual stress distribution.