Phase-Multiplied Photoelastic and Series Interferometer Arrangement for Full-Field Stress Measurement

Abstract

A compact, phase-multiplied, circular polariscope and series interferometer arrangement is developed for high-resolution, full-field stress measurement in single crystals with weak piezo-optical coefficients. We present a general stress-optic law, derived from anisotropic piezooptical constitutive relations, which provides the theoretical framework for obtaining stress field components from measured optical isoclinic, isochromatic and isopachic phase maps. A new phase image processing technique is also developed, which combines data obtained from different interference configurations for the successful removal of low-modulation zones within isoclinic and isopachic phase maps. The validity and accuracy of the proposed interferometer arrangement and stress measurement methodology are demonstrated through a compression test of a c-cut single crystal sapphire plate loaded by a cylindrical indenter.

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