Study of Residual Stress Distribution by a Combined Method of Moiré Interferometry and Incremental Hole Drilling, Part II: Implementation

Abstract

An experiment is devised to implement the combined method of moiré interferometry and incremental hole drilling which was proposed in the companion paper. A unique experimental apparatus is designed to combine an optical set up for moiré interferometry with an incremental hole-drilling device. The apparatus maintains a constant relative position of a drilling device to the specimen while alternating moiré interferometry measurements with incremental hole drilling. The drill-bit can reenter the hole for each incremental step. The incremental hole-drilling device produces a precise control of incremental hole depth with an accuracy of 0.1 μm. The method is utilized to measure the residual stresses of two shot-peened materials: AS10U3NG aluminum alloy and the ten percent SiCp reinforced aluminum composite-F3K10S Duralcan with a T6 heat treatment. Moiré fringe patterns with excellent contrast and high signal-to-noise ratio are obtained, which allows the extraction displacement data at the points very close to a hole boundary. In the experiment, a total number of ten steps of incremental hole drilling with an identical increment of 0.1 mm are performed. The fringe patterns of Ux and Uy displacement fields are recorded after each increment and the displacement data at the points of r = 1.2r0 are extracted consequently. They are used to determine the nonuniform residual stress distributions of surface and subsurface layers of shot-peened materials. The results indicate that the medium level of approximately equibiaxial compressive residual stresses exist within a 0.3 mm layer.