A micropolariscope for automatic stress analysis

Abstract

A micropolariscope has been developed for the automatic analysis of photoelastic data. It will position frozen stress slices mounted on its stage to within ±0.002 mm, and takes readings of isoclinic angles and fractional fringe orders, repeatable to within ±0.08 degrees and ±0.001 fringes. A rectangular grid of up to 3 × 50 points can be read automatically, taking about 1¼ minutes per point; the readings are stored on a floppy disc and printed out. The original slice is itself sliced, and the subslice is viewed again in the orthogonal direction to produce a second set of readings. Software has been devised to analyse the two sets of readings. It makes use of Tesar's modification of Frocht's Shear Difference method to calculate five cartesian stresses, which may be plotted and printed in tabular form. Flexible facilities are provided for editing, correcting, plotting, and printing intermediate stages in the analysis, and for storing results in data files