Generation of narrowband elastic waves with a fiber laser and its application to the imaging of defects in a plate

Hayashi, Takahiro; Ishihara, Ken

doi:https://doi.org/10.1016/j.ultras.2017.01.016

Generation of narrowband elastic waves with a fiber laser and its application to the imaging of defects in a plate

Hayashi, Takahiro; Ishihara, Ken

Ultrasonics, 2017, 77, 47-53

Number of Access:457（2025-08-14 18:27 Counts）

Identifier to cite or link to this item: https://hdl.handle.net/11094/84486

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Title	Generation of narrowband elastic waves with a fiber laser and its application to the imaging of defects in a plate
Creator	NRID 1000030324479 1000030324479 ORCID 0000-0001-6064-4658 0000-0001-6064-4658 researchmap permalink takahiro_hayashi takahiro_hayashi Scopus Author ID 37064150200 37064150200 CreatorName Hayashi, Takahiro
Creator	CreatorName Ishihara, Ken
Subject	Non-destructive evaluation
	Guided waves
	Laser ultrasonics
	Narrowband waves
	Scanning laser source technique
Abstract	Pulsed laser equipment can be used to generate elastic waves through the instantaneous reaction of thermal expansion or ablation of the material; however, we cannot control the waveform generated by the laser in the same manner that we can when piezoelectric transducers are used as exciters. This study investigates the generation of narrowband tone-burst waves using a fiber laser of the type that is widely used in laser beam machining. Fiber lasers can emit laser pulses with a high repetition rate on the order of MHz, and the laser pulses can be modulated to a burst train by external signals. As a consequence of the burst laser emission, a narrowband tone-burst elastic wave is generated. We experimentally confirmed that the elastic waves agreed well with the modulation signals in time domain waveforms and their frequency spectra, and that waveforms can be controlled by the generation technique. We also apply the generation technique to defect imaging with a scanning laser source. In the experiments, with small laser emission energy, we were not able to obtain defect images from the signal amplitude due to low signal-to-noise ratio, whereas using frequency spectrum peaks of the tone-burst signals gave clear defect images, which indicates that the signal-to-noise ratio is improved in the frequency domain by using this technique for the generation of narrowband elastic waves. Moreover, even for defect imaging at a single receiving point, defect images were enhanced by taking an average of distributions of frequency spectrum peaks at different frequencies.
Publisher	Elsevier B.V.
Source Title	Ultrasonics
Volume (Issue)	77
Page	47-53
Date of Issued	2017-05
Language	English
Handle URL	https://hdl.handle.net/11094/84486
PISSN	0041624X
NCID	AA00876332
Relation.isVersionOf	DOI (Publisher Version) https://doi.org/10.1016/j.ultras.2017.01.016
Relation.isIdenticalTo	PMID 28171791
Access Rights	open access
CopyRight	© 2017 Elsevier B.V. This manuscript version is made available under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
oaire:version	Accepted Manuscript
Category	学術雑誌論文 Journal Article

Resource Type	journal article
Local Type	Journal Article
DCMI Type	Text
DCTERMS.bibliographicCitation	Ultrasonics. 2017, 77, p. 47-53
DC.title	Generation of narrowband elastic waves with a fiber laser and its application to the imaging of defects in a plate
DC.creator	Hayashi, Takahiro
DC.creator	Ishihara, Ken
DC.publisher	Elsevier B.V.
DC.language' scheme='DCTERMS.RFC1766	English
DC.type' scheme='DCTERMS.DCMIType	Text
DCTERMS.issued' scheme='DCTERMS.W3CDTF	2017-05
DC.identifier	https://doi.org/10.1016/j.ultras.2017.01.016
DC.subject	Non-destructive evaluation
	Guided waves
	Laser ultrasonics
	Narrowband waves
	Scanning laser source technique
DCTERMS.abstract	Pulsed laser equipment can be used to generate elastic waves through the instantaneous reaction of thermal expansion or ablation of the material; however, we cannot control the waveform generated by the laser in the same manner that we can when piezoelectric transducers are used as exciters. This study investigates the generation of narrowband tone-burst waves using a fiber laser of the type that is widely used in laser beam machining. Fiber lasers can emit laser pulses with a high repetition rate on the order of MHz, and the laser pulses can be modulated to a burst train by external signals. As a consequence of the burst laser emission, a narrowband tone-burst elastic wave is generated. We experimentally confirmed that the elastic waves agreed well with the modulation signals in time domain waveforms and their frequency spectra, and that waveforms can be controlled by the generation technique. We also apply the generation technique to defect imaging with a scanning laser source. In the experiments, with small laser emission energy, we were not able to obtain defect images from the signal amplitude due to low signal-to-noise ratio, whereas using frequency spectrum peaks of the tone-burst signals gave clear defect images, which indicates that the signal-to-noise ratio is improved in the frequency domain by using this technique for the generation of narrowband elastic waves. Moreover, even for defect imaging at a single receiving point, defect images were enhanced by taking an average of distributions of frequency spectrum peaks at different frequencies.
DC.rights	© 2017 Elsevier B.V. This manuscript version is made available under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
DC.format	84486
citation_title	Generation of narrowband elastic waves with a fiber laser and its application to the imaging of defects in a plate
citation_author	Hayashi, Takahiro
citation_author	Ishihara, Ken
citation_publisher	Elsevier B.V.
citation_language	English
citation_date	2017-05
citation_journal_title	Ultrasonics
citation_volume	77
citation_firstpage	47
citation_lastpage	53
citation_doi	https://doi.org/10.1016/j.ultras.2017.01.016
citation_pmid	28171791
citation_public_url	https://hdl.handle.net/11094/84486

Generation of narrowband elastic waves with a fiber laser and its application to the imaging of defects in a plate

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