Investigation of autofrettage process in Al 1050 specimens by finite element and experimental method

Autofrettage process can be used to introduce beneficial residual stress in the cylinder of thick-walled pressure vessels. In this study, an experimental autofrettage was assembled based on hydraulic performance, and then aluminum alloy (Al1050) specimens were subjected to autofrettage under different pressures. Also, to evaluate the behavior of the specimens under the autofrettage process, the specimens were modeled into the finite element software ABAQUS and for evaluation of the accuracy of the data obtained from the finite element method (FEM), a strain gauge mounted tangentially on the outer surface of the specimen was used. It was also observed that by applying optimal autofrettage percentage, the maximum of Von-Mises stresses in specimens can be reduced by about 27%. Although in the non-autofrettaged specimens, the maximum stresses occur in the inner wall of the specimen, but by applying the autofrettage process, in addition to reducing the maximum amount of these stresses, the maximum amount can be transferred to the outer wall, which it is very important because the majority of fatigue cracks are formed in the inner wall of specimens.