An Axisymmetric Stress Release Method for Measuring the Autofrettage Level in Thick-Walled Cylinders—Part I: Basic Concept and Numerical Simulation

Abstract

A new experimental method for measuring the level of autofrettage in thick-walled cylinders is suggested. The method is based on measuring the hoop-strain while axisymmetrically releasing the residual stress field prevailing in the cylinder’s wall. A parametric study of the proposed experimental procedure conducted by a finite element simulation yields a simple empirical relation, which readily enables determining the actual autofrettage level from the strain measurements. This relation is found to be practically unique for all relevant cases, i.e., cylinders with radii ratios of b/a =1.6÷2.2 and autofrettage percents of φ=50–100 percent. A pilot test conducted on a 105-mm autofrettaged gun barrel, which experimentally validates the proposed procedure, is presented in Part II (Perl and Arone, 1994) of this paper.