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FL 200 Photoelastic experiments with a transmission polariscope



  • Photoelastic experiments on models subjected to mechanical loading
  • Monochromatic or white-light illumination1 
  • Creation of stress patterns with plane or circular polarised light
  • Determination of principal stress difference1
  • Various plastic models as accessories, e.g. wrench, bow, notched bars
  • Models to investigate specific issues can be easily made by users
  • Well structured instructional material


Technical Description

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.

FL 200 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 shone 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.

FL 200 permits flexible experimental setups even with self-made models. 

Learning Objectives / Experiments

- generation of planar stress states in various models under load
  * bending, tensile load, compressive load
- investigation of diffusion of stresses with plane or circular polarised light
- interpretation of photoelastic fringe patterns
  * stress concentrations, zero points, neutral fibres, areas of constant stress, stress gradients
- determination of occurring stresses and strains graphically and arithmetically


[1] representation of mechanical distribution of stress in photoelastic experiments
[2] 2 plane polarisation filters as polariser and analyser
[3] 2 quarter wave filters to generate circular polarised light
[4] all filters with 360° angle scale and marking of the main optical axis
[5] white light generated using a fluorescent tube and two incandescent lamps
[6] monochromatic light (colour yellow) generated using a sodium vapour lamp 
[7] filters roller bearing mounted and rotating
[8] frame cross-arms height-adjustable
[9] generation of compression or tension forces by means of a threaded spindle 
[10] complete models in polycarbonate (PC) for demonstration purposes available as accessories  

Technical Data
Light source
- lamp box with white diffuser
- for white light
  1 fluorescent tube TL-E 32W/33 (colour: 33)
  2 incandescent lamps, candle bulb, matt inner E14, 235V, 25W 
- for monochromatic light (colour yellow)
  1 sodium vapour lamp SOX 35, 35W
Filter, enclosed in glass, diameter: d=425mm
- 2 polarisation filters (dark olive)
- 2 quarter wave filters (colourless) 
Frame WxH: 600x750mm

Dimensions and Weight
LxWxH: 800x600x750mm
Weight: approx. 50kg Required for Operation 230V, 50/60Hz, 1 phase or 120V, 60Hz/CSA, 1 phase

Scope of Delivery
1 frame with load application device
2 polarisation filters
2 quarter wave filters
2 filter holders
1 light source
1 set of instructional material

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