The solution of crankcase fatigue strength problems improposed by long life reliability requirements of Military Standard Engines demands thorough stress analysis. Photoelastic methods were selected as the only basic, contemporary, nondestructive approach that ecomonically presents usable static and dynamic stress analyses permitting design engineers to use mass methods of production. This paper describes the technique as applied to die case crankcases and contains examples of stress determination by measurement of assembly, inertia, combustion, and thermal strains. Included is the application of the plastic, the instrumentation required, and interpretation of the results.
