Stress Analysis by Three-Dimensional Photoelastic Methods

This paper describes the results of an investigation and extension of the various proposed procedures and methods of analysis for the photoelastic determination of three-dimensional states of stress. Two important limitations of the previous developments are removed. A true extension to three dimensions is given by the determination of the effect on retardation of appreciable variation in the orientation of the secondary principal stresses in planes perpendicular to the wave normal (such variation being the rule rather than the exception for general states of stress). Also, methods for the analysis of whole planes are presented, thus avoiding the cumbersome and tedious point by point procedures that have been advanced. In the particular case of plane stress, these methods reduce to a purely optical technique for determining the principal stresses themselves, or more easily their sum, for the entire model.