Study of residual stress distribution by a combined method of moire interferometry and incremental hole drilling, part I: Theory

A new method combining Moire interferometry and the incremental hole-drilli ng method is developed to determine both uniform and nonuniform residual st ress distribution in depth. The study is reported in two parts. In this fir st part, the theoretical development of the moire interferometry hole-drill ing method is presented. The relationship between the in-plane surface disp lacements produced by introducing a blind hole and the corresponding residu al stresses is established by employing the existing theoretical solution c ontaining a set of undetermined coefficients. The coefficients are calibrat ed by the three-dimensional finite element method and they are processed no ndimensionally for general use. The whole field in-plane surface displaceme nts data U-x and U-y produced by the relaxation of residual stresses are ob tained from moire interferometry after each increment of hole drilling. The high signal-to-noise ratio provided by moire interferometry allows accurat e determination of fringe orders near the hole boundary which is essential for enhancing fidelity of residual stress determination. The experimental p rocedure to determine the signs of residual stresses is described and the a ccuracy of the method is also discussed.