Determination of 2D Directional Field of Three-point Bending Beam with Three-stepped Data in Digital Photoelasticity

Abstract

This paper is to present a three-step color phase shifting approach for automaticdetermination of the directional field of stresses based on the results of a digitally photoelasticexperiment. A plane polariscope with a white light source is used for recording the necessarilyphotoelastic fringe patterns. Relevant theories of the irradiance equations based on the use ofthe plane polariscope are derived. The obtained wrapped range of the isoclinic parameter isunwrapped to get the physical range by the unwrapping process. The obtained results in thephysical range are compared to those obtained from the four-step phase shifting technique.The unwrapped results show that the method proposed herein provides reasonable accuracy.