Machining effect of the autofrettaged compound cylinder under varying overstrain levels

The autofrettage process is used for the internal forming and sizing of cylinders designed to withstand high internal pressures. Once a tube is autofrettaged, it needs to be machined to its final dimensions on the bore and also on its outer surface. This paper presents an analytical and numerical study of a machined compound cylinder by using the finite element code, ANSYS10.0. An analytical model for predicting the level of autofrettage, either inner, outer, or combined machining of the compound cylinder is developed as the autofrettage residual stress field is simulated by an autofrettaged pressure. The autofrettaged pressures are obtained by using a trial and error method. When autofrettage is at 20%, the numerical results are found to be close in accordance to the analytical results. However, as the autofrettage is raised to 60%, the numerical results differ slightly to the analytical results. (c) 2007 Elsevier B.V. All rights reserved.