Method for measuring residual stresses in materials by plastically deforming the material and interference pattern comparison
OwnerMartin J. Pecherskyinventor
Life of this patent
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Abstract
A method for measuring residual stress in a material comprising the steps of establishing a speckle pattern on the surface with a first laser then heating a portion of that pattern with an infrared laser until the surface plastically deforms. Comparing the speckle patterns before and after deformation by subtracting one pattern from the other will produce a fringe pattern that serves as a visual and quantitative indication of the degree to which the plasticized surface responded to the stress dung heating and enables calculation of the stress.
Claims19
A method for producing a visual indication of stress in a surface of a material, said method comprising the steps of:
- dividing light from a first laser into two beams;
- directing said two beams onto said surface to establish a first light interference pattern;
- recording said first interference pattern;
- heating a portion of said surface sufficiently to deform said plastically;
- directing said two beams of light onto said portion to establish a second interference pattern on said portion;
- recording said second interference pattern;
- and
- comparing said first and said second interference patterns to determine visual differences between said first and said second interference patterns as a result of said deformation.
A method for producing a visual indication of stress in a surface of a material, said method comprising the steps of:
- directing two beams of light from a single laser onto said surface to establish a first light interference pattern;
- recording said first interference pattern in the form of binary bit values;
- directing light from an infrared laser onto a portion of said surface to heat said portion whereby said portion will deform plastically in response to said stress;
- directing said two beams of light onto said portion to establish a second interference pattern on said portion;
- recording said second interference pattern in the form of binary bit values;
- and
- subtracting bit values of said first interference pattern from bit values of said second interference pattern whereby said difference in bit values results in a fringe pattern indicative of said stress.
A method for measuring stress in a surface of an object, said method comprising the steps of:
- dividing light from a first laser into two beams;
- directing said two beams onto said surface to produce a first interference pattern;
- recording said first interference pattern in the form of binary bit values;
- directing light from a second laser on said surface to heat said surface, second laser being an infrared laser;
- directing said two beams onto said surface to produce a second interference pattern;
- recording said second interference pattern in the form of binary bit values;
- subtracting bit values of said first interference pattern from bit values of said second interference pattern to produce a fringe pattern indicative of said stress in said surface;
- and
- calculating said stress from said fringe pattern.
Dependencies are inferred from the claim text.