Analytical and Numerical Investigation of Stress Distribution in Hydraulic Autofrettage Process

This study represents comprehensive investigations of the stress distribution for a heavy-weapon-barrel in hydraulic-autofrettage process by means of analytical and numerical methods. Analytical equations are employed to calculate elastic-plastic junction radius and optimum autofrettage-pressure. Stress distributions are calculated with certain equations specific to each stage of loading, unloading and working-pressure application. In both analytical and numerical model, bilinear-kinematic-hardening material model, plane-strain model, and Von Mises-yield-criteria are used. The investigation matrix includes a wide range of four main parameters: barrel diameter, yield strength of barrel material, autofrettage- pressure and working-pressure. The effects of these parameters on autofrettage process are presented in a comparative manner. There is a 36% reduction of Von Mises stress for autofrettaged barrel under working pressure. With increasing barrel diameter, the maximum Von Mises stress parabolically increases and its location moves to the barrel inner radius when working pressure is applied. Radius of elastic-plastic junction is directed towards the inner radius with increasing yield strength.