Residual stress evaluation using shearography with large-shear displacements

A newly developed optical method for the qualitative and quantitative evaluation of residual and live-load stresses is presented. The method utilizes shearography employing a large angle shearing prism which results in large shear displacements. The large angle shearing prism allows the surface speckle pattern to be referenced and mapped onto a remote, separately positionable, surface. Changes on the object surface are initiated between exposures by means of a spherical impression made into the surface. The impression is made by impacting a hardened ball into the surface producing local stresses approximately three times the magnitude of the yield stress for the material. The deformation pattern is recorded and related to the stress that was initially present in the specimen. Copyright (C) 1996 Elsevier Science Limited.