Identification of inconsistent zones in digital photoelasticity

The condition for the occurrence of inconsistent zones when all the stresses are known is found based on the Mohr's circle of stress, and a new concept of inconsistency map is introduced. To verify the appearance of inconsistent zones experimentally, ten-step phase-shifted images are recorded using a monochrome CCD camera. Because of experimental difficulties, the boundaries of the inconsistent zones are not as smooth as in the analytical results. The experimental dark field isochromatics and wrapped isoclinic phasemap reveal that the stress field is very complex making the identification of inconsistent zones very difficult. The inconsistency map is useful in identifying the inconsistent zones and selecting a suitable seed point for unwrapping to obtain the unwrapped experimental isoclinic phasemap, which is then smoothed using the outlier smoothing algorithm.