Photoelastic stress analysis
AssigneeRover Group Limited
InventorsBarrie C. Stockley, Clive H. Buckberry
Life of this patent
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Abstract
Polarized light from a polarizer 12 is passed through a stressed birefringent object 14 and an analyser 16 to produce a fringe pattern representative of the stress in the object 14. The fringe pattern is observed with a CCD camera 18 and intensity information of the pattern is input to a computer 22. The process is repeated for at least two wavelengths of light and the information for the different wavelengths is combined to form a stress map of the object 14 for display on a VDU 24.
Claims15
A method for measuring stress in an object of birefringent material the stress having magnitude and direction, the method comprising the steps of passing polarized light of first, second and third wavelengths through the object and then an analyzer to produce respective fringe patterns, for each wavelength measuring and recording intensities of light emitted from the analyzer for a plurality of positions in the respective fringe pattern and combine the recorded intensities for the first, second and third wavelengths to form a ramp map having a discontinuity at predetermined values of stress and converting the ramp map to a stress map indicating the magnitude of the stress in the object as a function of position within the object.
Apparatus for measuring stress in an object of birefringent material comprising:
- a source of polarized light of first, second and third wavelengths;
- an analyzer, having an analyzer direction, for transmitting a component of the light, emitting from the object, which is parallel to the analyzer direction thereby to form a fringe pattern;
- light detecting means for measuring intensities of light emitted from the analyzer for a plurality of positions in the fringe pattern;
- a memory for storing the intensities;
- and processing means for combining the intensities for said first second and third wavelengths to form a ramp map having a discontinuity at predetermined values of stress and converting the ramp map to a stress map indicating a magnitude of the stress in the object as a function of position within the object.
Dependencies are inferred from the claim text.