Abstract
The simplest equipment, the best model materials, and the most effective techniques for three-dimensional photoelastic tests are described. The optical equipment involves only a simple diffusion polariscope using only a single camera lens. Phthalic anhydride-cured epoxy resins, which are relatively easy to cast in large sizes, have much superior properties for photoelastic tests than previously used materials. A simple technique of using surface slices and normal incidence of light will give adequate results for the stresses on free surfaces. At interior points, the effective stress can be obtained by measuring the retardation and isoclinic parameters on the three faces of random oriented small cubes. Some discussion is given regarding methods of applying the photoelastic results in practical design applications where fatigue, repeated strain cycling, plastic flow, and creep-rupture effects may occur during operation.