An Axisymmetric Stress Release Method for Measuring the Autofrettage Level in Thick-Walled Cylinders—Part II: Experimental Validation

Abstract

The basic concept of a new experimental method for measuring the level of autofrettage in thick-walled cylinders as well as a comprehensive numerical simulation were presented in Part I of this paper. A pilot test is conducted herein on a 105-mm autofrettage gun barrel to validate the proposed procedure. First, a preliminary test is performed to determine the minimum thickness required for a ring, cut from the barrel, in order to be a representative, valid, and free of edge-effect specimen. Then, the main experiment is conducted consisting of the gradual release of the residual stress field due to autofrettage prevailing in the ring specimen. An array of seven equally spaced, identical, radial notches is progressively cut at the inner surface of the ring, while the released hoop stress is continuously measured by a strain gage-based computerized data acquisition system. The process is accomplished by a detailed numerical simulation enabling a qualitative and quantitative monitoring of the procedure. The proposed experimental procedure is found to be feasible, reliable, and cost-effective, and to yield accurate results.