Whole-field digital measurements of isochromatics and isoclinics in photoelastic coatings

Whole-field digital determination of fringe order and principal stress direction in photoelastic-coating fringe patterns is studied. Two-wavelength method and polarization-stepping method are introduced to automate the determination of fringe order and the principal stress direction. The theoretical aspects related to the implementation of the two digital methods to the coatingʹs fringes is outlined. Experimental demonstration of the methods on a circular disk subjected to compressive loading is performed. Test results are given and compared well to the results measured manually.