Stress-gauging devices

Claim 1

A STRESS GAUGING DEVICE FOR RESOLVING THE VARIABLE MAGNITUDE OF A PARTICULARLY DIRECTED STRESS AT A WORKPIECE SURFACE, SAID DEVICE COMPRISING A FLAT-WASHER-SHAPED UNITARY TESTPIECE STRATUM OF PHOTOELASTIC MATERIAL, SAID STRATUM HAVING UPPER AND LOWER PLANE SURFACES, A RIGHT CYLINDRICAL INTERNALLY REFLECTING SURFACE AND A CONICAL INTERNALLY REFLECTING SURFACE, SAID STRATUM BEING ADAPTED FOR ATTACHMENT THROUGHOUT SAID LOWER PLANE SURFACE ONLY TO THE WORKPIECE SURFACE SO THAT SAID LOWER PLANE SURFACE IS STRAINED SUBSTANTIALLY EQUALLY WITH THE WORKPIECE SURFACE WHEN THE LATTER IS THEREAFTER DEFORMED, AND POLARIZING MATERIAL MEANS CONTIGUOUS WITH SAID UPPER SURFACE, SAID SURFACES BEING ORIENTED SO THAT LIGHT DIRECTED THROUGH SAID POLARIZING MATERIAL MEANS TO SAID CONICAL REFLECTING SURFACE IS DIRECTED NORMALLY OF SAID CYLINDRICAL REFLECTING SURFACE TO SAID CYLINDRICAL REFLECTING SURFACE AND FROM THE CYLINDRICAL REFLECTING SURFACE TO THE CONICAL REFLECTING SURFACE AND OUT OF SAID TESTPIECE AND THROUGH SAID POLARIZING MATERIAL MEANS.