This unit is used to view and measure the principle stress components and directions of principal stresses by photo elastic method for the plane stress condition at any given point in a photo elastic sample.
Photoelasticity is a tried and proven method of analysing and recording mechanical stresses and strains in components. It is deployed for quantitative measurement and to demonstrate complex stress states. The components used are models made of transparent, photoelastically sensitive plastic which becomes optically double-refractive under mechanical loading. SM-1414 is used to perform photoelastic experiments on flat, transparent plastic models. The models are subjected to loading by external forces, and have circular polarised light pass through them. An analyser analyses the light which has penetrated the body.
The experimental setup comprises the following components: A light source, four filters (to generate circular polarised light) and a frame inside which the models are attached and subjected to loading. The light source optionally permits coloured stress patterns with white light or light / dark representation with monochromatic light.
The combination of a polarisation filter and a quarter wave plate generates circular polarised light. Behind the model is a second quarter wave plate (perpendicular to the first one), combined with a second polarisation filter. The filters are mounted on rotating bearings and provided with angle scales.
Various models are mounted inside the frame. A load application device applies bending, tensile or compressive load to the model by way of a spindle. Stresses and strains occurring in the model are identifiable as bright spots, visualising the distribution of stress. To determine the principal stress difference, the order of the dark isochromatics is evaluated. SM-1414 permits flexible experimental setups even with self-made models.