Abstract: A contact gauge utilizable for determining contact pressure conditions between two bodies at their interface including a thin plastic sheet capable of memorizing an induced birefringence and a thin, load transmitting member attached to the sheet for inducing the birefringence therein. A method of employing the contact gauge for determining the contact pressure conditions between the two bodies also forms a part of the present invention.

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: Method comprises (1) introducing a polarized light beam into the convex surface of an optically-transparent body whereby the beam propagates in the body in a guided manner near the surface, (2) extracting at least a portion of the beam from the body through the surface at a distance from where the beam was introduced, (3) sensing the change in polarization state of the extracted portion of the beam occurring during its propagation in the body, and (4) calculating the value of stress from the sensed change in polarization state.

Abstract: At least four beams of linearly polarized light are produced separately at one and the same point of measurement in a single direction of observation at right angles to a unitary sheet of a specimen of photoelastic material in order to determine the state of mechanical stress in the plane of the sheet.

Abstract: A method and devices for sensing changes in separation of a first member relative to a second member, as well as variables causing such changes is disclosed. Electromagnetic waves diffracted by means included in said first member interact with waves from means included in said second member to form a characteristic interference pattern. Measured changes in this pattern allow determination of changes in separation.

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.

Abstract: A method and apparatus are described for indicating or measuring contact pressure distribution over a surface, in which method and apparatus, a pressure-transmitting member having a plurality of point-contact projections is used to transmit the contact pressure, in the form of a plurality of localized points, to a photoelastic member. The photoelastic member is one whose optical properties are changed when the member is subjected to pressure, and the changes in optical properties are optically displayed by directing polarized light onto the photoelastic member to produce interference patterns at the localized points of contact pressure.