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

A new method combining Moiré interferometry and the incremental hole-drilling method is developed to determine both uniform and nonuniform residual stress distribution in depth. The study is reported in two parts. In this first part, the theoretical development of the moiré interferometry hole-drilling method is presented. The relationship between the in-plane surface displacements produced by introducing a blind hole and the corresponding residual stresses is established by employing the existing theoretical solution containing a set of undetermined coefficients. The coefficients are calibrated by the three-dimensional finite element method and they are processed nondimensionally for general use. The whole field in-plane surface displacements data U_x and U_y produced by the relaxation of residual stresses are obtained from moiré interferometry after each increment of hole drilling. The high signal-to-noise ratio provided by moiré interferometry allows accurate determination of fringe orders near the hole boundary which is essential for enhancing fidelity of residual stress determination. The experimental procedure to determine the signs of residual stresses is described and the accuracy of the method is also discussed.