Whole-area photoelastic analysis by image processing on the principal-stress direction and separation of isochromatics from isoclinics.

In order to perform an accurate stress analysis in the framework of photoelasticity with computer-aided image processing, it is desireble to obtain the difference of the principal stresses and their directions over the whole area of the model, comparing the calculated result with the experimental data visually in each step of processing. The authors, in this paper, would like to focus on the classical photoelastic method with a plane polariscope. The subjects discussed are as follows : 1) to devise an explicit description of an equation for the direction angle of the principal stresses, analyzing the structural equation of the intensity of light in a plane polariscope, 2) to establish an algorithm for the calculation of the principal-stress direction over the whole area of the model, 3) to verify the effectiveness of the algorithm through various applications with experimantal data, 4) to present a method for more accurate and reliable separation of isochromatic fringes from isoclinic fringes, and, finally, 5) to propose a new method for computer-aided photoelastic analysis which can utilize a limited number of isoclinic patterns.