Phase measurement method for stress analysis from photoelastic data

Abstract

In recent years, phase measuring techniques have been applied to the problem of extracting information from photoelastic data. In this work, a complete method for stress analysis from photoelastic fringe patterns is presented. The photoelastic phase maps are obtained with a circular polariscope. For the isoclinics calculation a four-step phase-shift algorithm is used. A white light source is used to avoid problems of low modulation in the fringe pattern. Isochromatics are calculated by a new algorithm developed by us that overcomes the problems associated to low modulation areas produced by isoclinics. The isochromatic parameter can be determined without sign ambiguity. We have also developed a method for analysis of the measurement errors produced by errors in the elements of the polariscope. Finally, using the equilibrium equations, we can obtain the values of the main stresses in the sample from the isoclinic and isochromatic parameters.