Two-dimensional in-plane electronic speckle pattern interferometer and its application to residual stress determination

Based on the dual-beam illumination principle of Leendertz, an electronic speckle pattern interferometer (ESPI) is developed to de- termine separately two orthogonal components of the in-plane displace- ment field. In the arrangement described, the lengths of the illumination beams were reduced to make the optical setup compact. The CCD cam- era for recording images is placed outside the area enclosed by the optical path, and adequate working space is provided between the cam- era and the test rig, so that adjustments can be made without interfering with the light beams. Using a customized telephoto lens, different areas in the range of 5.634.0 and 14310 mm 2 can be examined at a distance of 550 mm from the test piece. Combined with the blind-hole-drilling method, it is applied to residual stress determination, which is a chal- lenging task due to stress concentration and severe decorrelation in the area neighboring the drilled hole.