RESEARCH ON EIGHT-STEP PHASE SHIFTING TECHNIQUE IN DIGITAL PHOTOELASTICITY AND ITS APPLICATIONS

The problem of isoclinic-isochromatic interaction is important in phase-shifting techniques in photoelasticity.A comprehensive discussion on the reason for the formation of ambiguous zones is presented.To separate isoclinic angle from the ambiguous fringe pattern,a technique named eight-step phase shifting is presented.Eight isoclinic images coupled with isochromatics are recorded by CCD(Charge Coupled device)camera from a plane polariscope with five different settings.The whole-field single isoclinic phase map in the range of [0,π/2] is obtained based eight maps.The feasibility of this method was proved by the simulation of a circular disk under diametral compression and the experiments of frozen disk,and the information of whole-field isoclinic can be extracted automatically.