Completely automated determination of two-dimensional photoelastic parameters using load stepping

Abstract

The new approach to phase-stepping photoelasticity known as ‘‘load stepping’’ is used to determine automatically the isochromatic parameter a and the isoclinic angle ?. There is no need for the user to calibrate the results other than to convert the isochromatic parameter into a principal stress difference using the material fringe constant. Four phase-stepped images are collected using a circular polariscope for each of three load steps, which differ by small equal increments. A ramped phase map for the isochromatic parameter is produced in the range -?