Mathematical Morphology Guided Automatic Unwrapping Isoclinic Phase Map in White Light Photoelasticity

Abstract

By comparing the results calculated by atan() and atan2() functions, the correctly estimated region of isoclinic phase map is determined using morphological techniques. The isoclinic phase map is automatically unwrapped in the true phase range -π /2 to π /2. Demonstrations of the method on a disc and a ring under diametral compression are performed. Test results compare well with the theoretical results. Furthermore, the influences of principal stress direction and the range of isoclinic phase upon stress separation are discussed.

Full-field stress determination in photoelasticity with phase shifting technique

“…However, in order to obtain an accurate phase map for the isochromatics, the orientation of the maximum principal stress should be known. For instance, Liu et al proposed a mathematical morphology guided method to unwrap the isoclinic phase [12]. Shang et al developed a MOD equation to solve the problems related to discontinuity of the isoclinic phases realized in the inverse tangent calcul ation, as well as the influence of the isochromatic parameter in the plane polariscope [13].…”