Autofrettage of nonlinear strain-hardening cylinders using the proposed analytical solution for stresses

This paper focuses on pressurized thick-walled cylinders with nonlinear strain-hardening behavior. At first, a constitutive model is proposed to capture the test data done on the steel specimen. It is shown that this model is able to cover the various specific behaviors such as the perfect plastic, linear hardening, and nonlinear hardening behaviors. This constitutive model due to high performance in constitutive modeling and simplicity of its mathematical form is applied to pressurized thick-walled cylinders in order to find a closed-form analytical solution for their analysis. For this purpose, elasto-plastic stresses distribution in pressurized thick-walled cylinders made of a nonlinear strain-hardening material is obtained analytically for both loading and unloading phases using Tresca's yield criterion and considering the Bauschinger effect. Then, the solution is compared with experimental data and good agreement between predicted results and experimental data is observed. In the following, the residual stresses distribution are obtained to determine the best level of autofrettage for strengthening and design of these thick-walled cylinders prior to industrial use with the aim of increasing strength-to-weight ratio. It was observed that the parameters such as the material behavior (stress strain curve) and the Bauschinger effect have a significant influence on the results.