High sensitivity moiré interferometry and incremental hole-drilling method for residual stress measurement

The theoretical development of a combined method of moiré interferometry, Twyman–Green interferometry and incremental hole-drilling method is presented. The relationship between the three-dimensional surface displacements produced by introducing a blind hole and the corresponding residual stress is established by employing the existing theoretical solution containing a set of undetermined coefficients. The in-plane surface displacements $\text{U}{}_{\mathrm{x}}$ and $\text{U}{}_{\mathrm{y}}$ and out of plane surface displacement $\text{U}{}_{\mathrm{z}}$ produced by the relaxation of residual stresses are obtained from moiré interferometry and Twyman–Green interferometry respectively. The accuracy of the method and the experimental procedure to determine the signs of residual stresses are described. A typical examp1e is presented.