Photoelasticity
information and
images courtesy of Measurements Group Inc.
Photoelasticity is a full-field technique used in stress analysis testing. When a photoelastic material is subjected to load and viewed with polarized light, colorful patterns are seen which are directly proportional to the stresses and strains in the material. This prismatic model with "C"-shaped offset is being loaded and unloaded in tension to produce isochromatic fringes indicative of the shear strains in the model.
From Epsilonics, Vol. III, Issue 3, Dec. 1983, Measurements Group, p. 11.