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1 December 1991 Lasers applied to photoelastic stress measurements
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An instrument to measure three components of the strain tensor at the surface of the examined body using the photoelastic effect has been developed. The method applied is based on the utilisation of three oblique incidence light beams from three laser diodes. The isochromatic fringes in the photoelastic coating are observed by three independent channels. The data collected in this way is used to define the state of strain and stress from one single point measurement. The measuring head equipped with three or more lasers scans the surface of the tested body and transfers the data on the light intensities into the computer memory. This data is then converted into the values of strains and stresses. The computer also controls the head motion. The obtained results (three components of the strain tensor), are presented in the form of diagrams on the screen of the monitor or using the plotter. The stresses are calculated from strains using the physical properties of the examined body. The device is equipped with a specially designed software for recording and processing the data. Application of the described device eliminates all problems with the separation of strain components in the photoelastic stress measurements. The apparatus is portable and provides the stress distribution in the examined body in a very short time.
© (1991) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Stan Lukasiewicz "Lasers applied to photoelastic stress measurements", Proc. SPIE 1554, Second International Conference on Photomechanics and Speckle Metrology, (1 December 1991);

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