Theoretical and Finite Element Analysis of High Pressure Components

Abstract

High pressure vessels such as gun barrels,high pressure diesel pumps are autofrettaged in order to increase their operating pressure and fatigue life. Autofrettage process helps in reducing the stress level. Autofrettage process causes plastic expansion of the inner radius of the cylinder,thereby establishing the beneficial residual compressive stresses at the bore after the de-pressurisation.The stresses developed during the subsequent pressure application,has to overcome these compressive stresses before the tensile stresses can be developed. For autofrettaged cylinder, the depth of plastic zone, or overstrain is a key factor which affects load-bearing capacity and safety. In the current paper work, numerical simulation of the Autofrettage process was applied on to a cylinder of known dimensions with an objective to provide a better understanding of the stresses that are developed at high pressure.A comparison of reduction in stress levels between a Autofrettaged and Non-Autofrettaged cylinder has been done.It is observed that there is a reduction of 15.7% in maximum stress level for a Autofrettage pressure of 200MPa and an operating pressure of 180MPa. Also the maximum and minimum Autofrettage pressure required for autofrettage process to be carried out effeciently and the postion of maximum stresses for different autofrettage pressures have been discussed.