Experimental and numerical analysis of autofrettage process for thick walled cylinders

Experimental and numerical and analysis of autofrettage process for thick-walled cylinders is presented in this study. Autofrettage tests are carried out on a hydraulic autofrettage test stand available in Delphi Automotive Systems in İzmir. AISI 4140 steel is used as the test material in the experiments. The samples are produced from a solid cylindrical bar with 10mm inner diameter, 30mm outer diameter and 200mm long. Eight different autofrettage pressures in the range between 530 to 666 MPa are used in the tests. Axial and tangential strains are measured during the tests in order to see the changes in strains with both autofrettage pressure and pressure holding time. Residual stresses developed on the wall of the cylinders due to autofrettage pressure are measured at five different points along the wall of the cylinders by using X-ray diffraction method. Radial and tangential residual stress distributions are plotted in order to see the effects of autofrettage pressure. A finite element model is also created by using ANSYS® Workbench 15.0 to compare the experimental results with the numerical results. 2D axisymmetric analyses are performed for each autofrettage condition. Measured strains during the tests and results obtained from numerical model are found to be almost the same. The tendency of change in the distribution of residual stresses is found to be similar for experimental and numerical results.