Evaluation of fatigue damage using laser speckle: relation between surface profile and diffraction pattern

Akira Kato; Fumihiko Okuya

doi:10.1117/12.429605

13 June 2001 Evaluation of fatigue damage using laser speckle: relation between surface profile and diffraction pattern

Akira Kato, Fumihiko Okuya

Proceedings Volume 4317, Second International Conference on Experimental Mechanics; (2001) https://doi.org/10.1117/12.429605
Event: Second International Conference on Experimental Mechanics, 2000, Singapore, Singapore

Abstract

We investigated a method to evaluate fatigue damage of steels without contact using laser speckle. In the earlier stage of fatigue in steels, slipbands appear on the surface and microscopic phase strain is stored in the slipbands. The slipbands appear more densely with progress of fatigue damage. When a laser illuminates surface of the fatigued steel, light intensity distribution of the laser speckle pattern formed by the reflected light changes with the change of surface properties caused by slipbands. It has been clarified that width of the speckle pattern broadens corresponding to spatial frequency distribution of the surface profile and thus it is presumed that speckle pattern broadness with increase of slipband density. This shows that we can detect fatigue damage by observing the laser speckle pattern broadens with increase of slipband density. This shows that we can detect fatigue damage by observing the laser speckle pattern on material surface. The method presented in this paper is based on this phenomenon. We observed change of surface property and the speckle pattern during fatigue loading under constant stress amplitude using steel specimens. Surface roughness and fractal analysis of the surface profile diagrams were obtained to evaluate surface property. Change of surface roughness and fractal dimension of the surface profile were compared to change of laser speckle pattern depending on progress of fatigue damage and relation between surface property and speckle pattern was investigated. We investigated possibility of evaluation of fatigue damage observing laser speckle pattern during fatigue.

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Akira Kato and Fumihiko Okuya "Evaluation of fatigue damage using laser speckle: relation between surface profile and diffraction pattern", Proc. SPIE 4317, Second International Conference on Experimental Mechanics, (13 June 2001); https://doi.org/10.1117/12.429605

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KEYWORDS

Speckle pattern

Radium

Surface properties

Surface roughness

Fractal analysis

Speckle

Laser induced damage

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