TECHNIQUES

An electronic speckle pattern interferometer hasbeen adapted for measuring residual stress. Thetechnique is based on the hole drilling method, anduses the ESPI system to convert the measured de-formation around the hole to a value of in-plane residual stress. In this 4-part series, we will describe a single beam ESPI system adapted specifically for measuring residual stress, an analysis technique, quantify some of the errors, and present results from measurements in ‘‘known’ ’ stress samples. The ESPI hole drilling technique can be much fas-ter than the strain gage hole drilling technique, is applicable to a wider range of materials and surfaces, and provides much more detailed information about the deformation that occurs as a result of the hole drilling. Because of these ben-efits, it is expected that the ESPI technique will allow for Fig. 1: I beam split by residual stresses after angle-cutting the ends of the beam much better quantification of the accuracy, and provide a means for future advances in the science, such as optimi-zation of drilling techniques, adaptation of new drilling techniques, detection of sur-face gradients, etc