Abstract:

Phase shift is applied to calculate parameters from photoelastic fringe patterns. Stress components are determined with shear stress differential methods. In planar polariscope, four fringe patterns with specific angles are acquired and the phase map of the orientation of principal stresses derived from isoclinics according to four-step phase stepping. A method is proposed to determine orientation of the first principal stress in the entire field. Similar to Tardy compensation, isochromatic fringe patterns are analyzed in 8 discrete directions. In each direction, phase shift is achieved by rotating the analyzer in the circularly polarized field. With information of the orientation of the first principal stress, the phase map of isochromatics for the entire field is constructed from the 8 phase maps. Thus, stress components within the photoelastic model can be determined. An example is given to illustrate the merits of the proposed methods.

Key words: photoelasticity； phase shift； stress component