Application of the harmonic star method in photoelastic separation of principal stresses

This paper deals with automation of an experiment process by means of photoelasticity on the condition that only information which was previously collected by identification of isochromatic fringes is used. The analysis of this issue pointed to Poisson's and Laplace's equations. These equations were solved through the harmonic star method. The automation of an experiment was based on the development of a noncommercial program for processing of data which had been collected during photoelastic measurements. In addition, the program was used for verification of these measurements and comparison of measurement outcomes with results which were gained by the finite element method (FEM). Such a program enabled us to measure stresses in a certain point of the examined surface and, at the same time, separate these stresses, that is, determine the magnitude of individual stresses. A data transfer medium-a camera-was used to transfer the picture of isochromatic fringes directly into a computer. The chosen procedure of solving and evaluating the experiment provided us with reliable outcomes comparable to results gained by FEM.