Stress-difference elasticity and its application to photomechanics

The two-dimensional elasticity equations have been reformulated in terms of the obtainable photoelastic data and the first stress invariant. The result is a new group of partial-differential equations which can be used to either separate the stresses along a line segment or to generate photoelastic data within a region. The equations can also be used to check the quality of the data used in the shear-difference method. Examples which illustrate the use of these equations are presented and discussed.