- Photoelasticity is a proven method of analysing and recording mechanical stresses and strains in components. It is used both for quantitative measurements and for demonstrating complex stress states. The components used are models made of a transparent, photoelastically sensitive plastic, which becomes optically birefringent under mechanical load. SMT-SM-18 is used to conduct photoelastic experiments on plane, transparent plastic models. The models are subjected to load by external forces, and they are radiated by circular polarised light. An analyser analyses the light penetrating the body. The experimental setup comprises the separate components: a light source, two linear polarising filters (polariser and analyser), two quarter-wave filters, a frame in which the models are attached and subjected to load. The light source optionally permits coloured stress patterns with white light or a light/dark representation with monochromatic light.