A radial in-plane DSPI interferometer using diffractive optics for residual stresses measurement

Abstract

This paper presents a new configuration of a digital speckle pattern interferometer that uses a binary diffractive optical element (DOE) to achieve radial in-plane sensitivity. The use of the DOE ensures constant sensitivity to the interferometer since it only depends on the grating period and does not depend on the wavelength of the illumination source. The paper describes the principles as well as the concepts of a portable device that was integrated to a drilling module to apply the hole drilling method for residual stresses measurement. Comparative results showed that the combined system can measure residual stress fields with uncertainty comparable with the classical strain gage based hole drilling method, but at least four times faster. A practical application of residual stresses measurement outside the laboratory is briefly presented.