Residual stress measurements in an autofrettaged cylinder through the Initial Strain Distribution method

An experimental activity aimed at determining the complete residual stress field in an autofrettaged cylinder is reported and the obtained results are presented and discussed. A set of strain gauges were located on annular plates extracted from the cylinder in order to measure the relaxed strains produced by the gradual extension of a radial cut. The relaxed strains were related to the initial strain distribution induced by the autofrettage process by solving a set of integral equations with dedicated influence functions. In order to estimate the global errors and to assess the reliability of the obtained residual stress distributions, two nominally identical annular plates were subjected to similar tests. Experimental arrangements, including the strain gauges positioning and the machining set up of the cuts along with the post-processing of the relaxed strains are presented and the obtained results of the two tests are compared and discussed. The whole procedure appears suitable for an accurate evaluation of the residual stress distribution in the autofrettage component.