Study of Autofrettage Process Effect in Thick-walled Cylinder with Metal Matrix Composite by the method of Finite Element Cyclic Stress Analysis

In this study, numerical simulation of a thick cylinder, under thermo-mechanical cyclic loading has been performed. The applied boundary conditions are similar to the working gun barrel during continuous firing. Four stress conditions in 25-950 °C and 100-350 MPa pressure has been investigated. Conditions include first, without autofrettage and cracking; second, with autofrettage and without cracking; third, without autofrettage and with cracking; and fourth with autofrettage and with cracking has been investigated. Comparison of the results obtained from simulated models of the autofrettaged and non-auto-frettaged barrels has information about the evolution of strains and stresses in the barrel at different points under thermo-mechanical loading cycles in both cases. The materials in the barrel were ST50 steel and SiC/Ti-24Al-11Nb metal matrix composite in three different diameter ratios. The results showed that autofrettage softened the inner surface of the barrel. This phenomenon was seen as a decrease in the hardness of the inner surface of the barrel. The maximum stress of thermomechanical cyclic loading there was until 9 mm of depth. This depth is the active length of crack propagation.