Laser-induced surface acoustic wave technique for precise depth measurement of stress corrosion cracking

A new method to evaluate a crack depth is introduced. Surface acoustic wave generated by Q-switched Nd:YAG laser (wavelength: 532 nm) and detected by frequency-stabilized long pulse laser (wavelength: 1,064 nm) coupled with confocal Fabry-Perot interferometer is used to evaluate a depth of surface-b...

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Bibliographic Details
Published in:Journal of physics. Conference series 2011-01, Vol.278 (1), p.012009-5
Main Author: Ochiai, M
Format: Article
Language:English
Subjects:
Acoustic propagation
Austenitic stainless steels
Broadband
Cracks
Depth measurement
Error analysis
Fabry-Perot interferometers
Flaw detection
Frequency analysis
Frequency response
Lasers
Measurement methods
Neodymium lasers
Physics
Semiconductor lasers
Stainless steels
Steel plates
Stress corrosion cracking
Surface acoustic waves
Tensile stress
Wave propagation
Wavelengths
YAG lasers
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Summary:A new method to evaluate a crack depth is introduced. Surface acoustic wave generated by Q-switched Nd:YAG laser (wavelength: 532 nm) and detected by frequency-stabilized long pulse laser (wavelength: 1,064 nm) coupled with confocal Fabry-Perot interferometer is used to evaluate a depth of surface-breaking tight crack. When the generated surface acoustic wave propagates through a crack before it is detected, only the lower frequency component is observed at the detection point due to interaction between the broadband surface acoustic wave and shallow crack. Energy of surface acoustic wave penetrates about its one wavelength into the propagation medium; it means that surface acoustic wave with higher frequency component localizes only thin layer from the surface and one with lower frequency component easily travel through cracks if it is shallow. A frequency response analysis technique, as well as an amplitude response analysis, of the surface acoustic wave is developed to quantitatively evaluate the depth of cracks. Several stress corrosion cracks introduced on type 304 stainless steel plates by immersing corrosive solution with tensile stress are prepared to verify the performance of this method. The results demonstrate the error of this depth measurement method is estimated at less than 0.3 mm.
ISSN:1742-6596
1742-6588
1742-6596
DOI:10.1088/1742-6596/278/1/012009