Microstructure imaging using frequency spectrum spatially resolved acoustic spectroscopy (F-SRAS)

S. D. Sharpies, W. Li, M. Clark, Michael Geoffrey Somekh

Research output: Chapter in book / Conference proceedingConference article published in proceeding or bookAcademic researchpeer-review

2 Citations (Scopus)


Material microstructure can have a profound effect on the mechanical properties of a component, such as strength and resistance to creep and fatigue. SRAS - spatially resolved acoustic spectroscopy - is a laser ultrasonic technique which can image microstructure using highly localized surface acoustic wave (SAW) velocity as a contrast mechanism, as this is sensitive to crystallographic orientation. The technique is noncontact, nondestructive, rapid, can be used on large components, and is highly tolerant of acoustic aberrations. Previously, the SRAS technique has been demonstrated using a fixed frequency excitation laser and a variable grating period (k-vector) to determine the most efficiently generated SAWs, and hence the velocity. Here, we demonstrate an implementation which uses a fixed grating period with a broadband laser excitation source. The velocity is determined by analyzing the measured frequency spectrum. Experimental results using this "frequency spectrum SRAS" (f-SRAS) method are presented. Images of microstructure on an industrially relevant material are compared to those obtained using the previous SRAS method ("k-SRAS"), excellent agreement is observed. Moreover, f-SRAS is much simpler and potentially much more rapid than k-SRAS as the velocity can be determined at each sample point in one single laser shot, rather than scanning the grating period.
Original languageEnglish
Title of host publicationReview of Progress in Quantitative Nondestructive Evaluation
Number of pages8
Publication statusPublished - 1 Apr 2010
Externally publishedYes
Event36th Annual Review of Progress in Quantitative Nondestructive Evaluation, QNDE - Kingston, RI, United States
Duration: 26 Jul 200931 Jul 2009


Conference36th Annual Review of Progress in Quantitative Nondestructive Evaluation, QNDE
Country/TerritoryUnited States
CityKingston, RI


  • Acoustic imaging
  • Laser ultrasonics
  • Material characterization
  • Microstructure
  • Orientation imaging

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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