Moire interferometry assessement of residual stress variation in depth on a shot peened surface

The main goal of this work was the development of experimental techniques to measure in depth non-uniform residual stresses, as alternative to the more conventional hole-drilling method with strain gauges. The proposed experimental methodology is based on moire interferometry. This high resolution field technique allows in-plane displacement assessment without contact. Grating replication techniques were also developed to record high quality diffraction gratings onto the specimen's surface. A laser interferometry setup was implemented to generate the master grating (virtual). The stress relaxation was promoted by blind hole-drilling and the obtained fringe patterns were video recorded. Image processing techniques were applied to assess the in-plane strain full-field. A finite elements code (FEM), ANSYS (R), was used to simulate the stress relaxation process and to calculate the hole-drilling calibration constants