Photographic evaluation techniques in photoelasticity—Part 1

Abstract

Sharp boundaries or thin lines seen on high contrast or Agfacontour photographs of optical fringes are interpreted as equidensity lines and calibrated for fractional order or isoclinic angle. Systematic variation of exposure determinants changes their positions and parameters so that the entire photographed field can be evaluated from sets of photographs either taken directly or copied from one or a few low contrast negatives. Photogrammetry resolves spatial detail down to 0002mm spot size and relates photoelastic results to model outlines and deformation measured on the same films. The practical aspects of photography, exposure variations and evaluation are treated in this overview published in two parts. Part 1 covers photographic methods and application to isochromatics, Part 2 evaluation and calibration for fractional orders with examples, application to isoclinics and a summary of main features.