PHOTOELASTICITY STRESS-ANALYSIS USING CARRIER FRINGE AND FFT TECHNIQUES

A novel carrier fringe technique for photoelasticity stress analysis is described and verified experimentally. Linear carrier fringes generated by using a quartz wedge are superimposed on fringes formed by the stressed model. The resultant fringe pattern is then captured using a charge coupled device camera and stored in a digital frame buffer. A fast Fourier transform method is then used to process the complete photoelastic fringe image over the whole surface of the model. The experiment also uses a minimum spanning tree phase unwrapping strategy to create a continuous map of the whole stress field. Finally, the whole principal stress difference field has been calculated and plotted from one single exposure showing the methods' potential for use as a reflection analysis system suitable for application to nonstationary objects and complicated stress patterns.