Advancing instantaneous photoelastic method with color polarization camera

Abstract

Digital photoelasticity is an essential experimental method. For dynamic objects and transient stress fields, the utilization of the instantaneous photoelastic method becomes necessary. Existing instantaneous photoelastic methods, represented by the conventional RGB method and instantaneous phase shifting techniques, encounter a significant challenge in simultaneously obtaining both the isochromatic and isoclinic parameters while ensuring a considerable measurement range for the isochromatic fringe order (retardation). This severely limits the application scope of instantaneous photoelasticity. In this paper, a novel approach is proposed by introducing a color polarization camera into the field of photoelasticity. The proposed method enables simultaneous determination of the full-field continuous isochromatic fringe order and the isoclinic parameter, ensuring a considerable measurement range for the isochromatic fringe order. Additionally, the obtained isoclinic parameter is consistent, eliminating the need for tedious and time-consuming phase unwrapping procedures. To validate the accuracy and effectiveness of the method, it was applied to standard problems involving a disc and a ring under diametral compression and an instantaneous problem concerning a rotating blade. The proposed method expands the application potential of instantaneous photoelasticity, enabling the resolution of a broader range of problems.