Abstract: In the reflection polariscope using filter with four elements transmitting light of four different wavelengths each polarized in appropriate plane and a photoelastic coating having a built-in dichroic filter an image is recorded. The record is further processed in the Fourier processor using special filters to obtain certain potentials and/or the averaged strains in the photoelastic coating and strains in the coating-prototype interface.

Abstract: The filter comprises a multiplicity of light polarizing elements which polarize light in a plurality of planes, and a multiplicity of filtering means associated with the light polarizing elements. In a polariscope, light is directed from a source through such a filter to the specimen to be analyzed. Light passed through the specimen once or twice is coupled through another such filter termed an analyzer. In certain embodiments, the polarizer and the analyzer are combined. Patterns representing the stress in the specimen are produced. The pattern includes isochromatics and a number of isoclinics.

Abstract: There is disclosed a photoelastic strain gauge which displays visual patterns representative of the strain in the workpiece to which the gauge is bonded. The gauge comprises two sheets of reflective material and a body of photoelastic material therebetween. A reflector in the body directs polarized light in such a way as to be reverberated between the reflective sheets and then discharged to produce the visual patterns. Because the light is reverberated, the visual patterns are amplified or enlarged.

Abstract: The photoelastic strain gauge coating comprises a sheet of photoelastic material of predetermined shape having a multiplicity of minute discontinuities or sets of discontinuities arranged in a predetermined grid. The predetermined shape and grid, together with boundary devices, provide a standard format to enable use of supporting computer programs. In practicing the method, the coating is bonded to the workpiece surface to be analyzed, and then illuminated by polarized light and photographed. The photograph is then magnified greatly to enable examination seriatim of the patterns at and about each discontinuity or set of discontinuities. The data thus obtained is processed, using the supporting computer programs to obtain a strain field of the portion of the workpiece covered by the coating.

Abstract: The coating comprises a sheet of photoelastic material having a multiplicity of regions, in each of which is a plurality of measuring elements at predetermined angles. Each of the measuring elements has an abutment and a finger in operating contact with each other. There will appear in each finger patterns representative of the strain in the associated portion of the workpiece. These patterns are "read" and the values plugged into formulas to determine the magnitude of the strain in each of the two principal directions, and the angle of the principal directions.