Electronic techniques in isodyne stress analysis: Part 1. Basic relations

The purpose of the study was to develop electronic techniques for collecting, processing and evaluating information in experimental isodyne stress analysis. The original technique involved chemical photography recording and manual evaluation of the normal and shear isodyne functions and their derivatives, which are proportional to the stress components. One objective of the reported study was to show that it is feasible to reliably reconstruct isodyne surfaces which contain information on the internal force intensities and the components of the stress tensor. It is shown that the new technique satisfies all the theoretical conditions and constraints imposed by the theory of the analytical and optical isodynes. Thus another objective of the reported study was to demonstrate that the isodyne stress analysis allows one to obtain reliable data on the actual three-dimensional stresses in a cost-effective manner. The procedure developed to date and presented in the paper is a hybrid electronic-manual procedure. It involves electronic recording of the isodyne fields, manual determination of the isodyne orders in chosen sections, and electronic determination of the indicated and load-induced isodyne functions and of the isodyne surfaces. It is shown that the developed techniques are more reliable, accurate and cost-efficient than the traditional techniques of photomechanics. Pertinent data are illustrated by examples presented in Part 2.