Laser-ultrasonic detection of subsurface defects in processed metals
First Claim
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1. A laser-ultrasonic method for detecting a subsurface defect within a processed region of a metallic workpiece, comprising the steps of:
- generating a probe acoustic Rayleigh wave by directing a generation laser beam to a predetermined generation area on a surface of the metallic workpiece within the processed region;
detecting a direct-arriving and a scattered acoustic Rayleigh wave via an interferometer and a detection laser beam that impinges the surface of the metallic workpiece at a detection spot which is within the processed region and has a predetermined spatial relationship to the generation area;
repeating said step of generating and said step of detecting for a plurality of predetermined generation areas and detection spots on the surface of the metallic workpiece within the processed region; and
comparing the direct-arriving and scattered acoustic Rayleigh waves detected for at least two predetermined detection spots to detect the subsurface defect within the processed region of the metallic workpiece.
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Abstract
Subsurface defects in a processed metal are detected by a laser-ultrasonic method involving generation of a surface acoustic wave at one location on the processed metal surface, and detection of a scattered acoustic wave at another location on the processed metal surface. The method can be used in-line to provide real time monitoring of laser cladding and other metal processing operations.
50 Citations
15 Claims
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1. A laser-ultrasonic method for detecting a subsurface defect within a processed region of a metallic workpiece, comprising the steps of:
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generating a probe acoustic Rayleigh wave by directing a generation laser beam to a predetermined generation area on a surface of the metallic workpiece within the processed region; detecting a direct-arriving and a scattered acoustic Rayleigh wave via an interferometer and a detection laser beam that impinges the surface of the metallic workpiece at a detection spot which is within the processed region and has a predetermined spatial relationship to the generation area; repeating said step of generating and said step of detecting for a plurality of predetermined generation areas and detection spots on the surface of the metallic workpiece within the processed region; and comparing the direct-arriving and scattered acoustic Rayleigh waves detected for at least two predetermined detection spots to detect the subsurface defect within the processed region of the metallic workpiece. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A laser-ultrasonic device for detecting a subsurface defect within a processed region of a metallic workpiece, comprising:
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a generation laser providing a generation laser beam that impinges a predetermined generation area on a surface of the metallic workpiece within the processed region; a detection laser providing a detection laser beam that impinges the surface of the metallic workpiece at a detection spot which is within the processed region and has a predetermined spatial relationship to the generation area; an interferometer that detects direct-arriving and scattered acoustic Rayleigh waves via the temporal displacement of the surface of the metallic workpiece at the detection spot based on a phase shift of a portion of the detection laser beam reflected from the surface of the metallic workpiece; and an analyzer that compares the direct-arriving and scattered acoustic Rayleigh waves detected by the interferometer for at least two detection spots to detect the subsurface defect within the processed region of the metallic workpiece. - View Dependent Claims (15)
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Specification