Determination of Whole Field Residual Strain Measurement Using 3D-DSPI and Incremental Hole Drilling

An experimental setup utilizing 3D-Digital Speckle Pattern Interferometry (DSPI) ^1,2 and Incremental hole drilling is being applied for the non-contact, fast and accurate determination of residual strain as a function of depth. From the measured phase maps using the DSPI technique we can determine the surface deformations in a whole field area around a drilled hole and thus relate these released strains to the residual strains existing in the material. Incremental hole drilling^3,4 has been coupled with residual stress measurement to provide a means to estimate the residual stresses as a function of depth. Unlike the traditional holography with a manualevaluation⁵ in this case the system can quantitatively determine the deformation data in x, y and z directions for various depth increments and thus finally provides us with the residual strains as a function of depth. A 3D-DSPI unit coupled with a custom designed drilling system has been used in an experimental setup to study the residual strain distribution.