Abstract

We have developed a noncontact and nondestructive technique that uses laser-generated and detected surface acoustic waves to rapidly determine the local acoustic velocity, in order to map the microstructure of multi-grained materials. Optical fringes excite surface waves at a fixed frequency, and the generation efficiency is determined by how closely the fringe spacing matches the acoustic wavelength in the excitation region. Images of titanium alloys are presented, acquired using the technique. Methods to improve the current lateral resolution of 0.8mm are discussed, and the ability to measure velocity change to an accuracy of one part in 3300 is experimentally demonstrated.

© 2006 Optical Society of America

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References

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  1. M. G. Somekh, G. A. D. Briggs, and C. Ilett, "The effect of elastic-anisotropy on contrast in the scanning acoustic microscope," Philosophical magazine A-Physics of condensed matter structure defects and mechanical properties 49, 179-204 (1984).
    [CrossRef]
  2. C. F. Quate, "Acoustic microscopy: recollections," IEEE Trans. Sonics Ultrason. SU-32, 132 (1985).
    [CrossRef]
  3. R. S. Gilmore, Ultrasonic Instruments and Devices II, vol. 24 of Physical Acoustics, chap. 5, pp. 275-346 (Academic Press, San Diego, CA, USA, 1999). (Editors: R N Thurston and Allan D Pierce).
  4. S. Sathish and R. W. Martin, "Quantitative imaging of Rayleigh wave velocity with a scanning acoustic microscope," IEEE Trans. Ultrason. Ferroelectr. Freq. Control 49, 550-557 (2002).
    [CrossRef] [PubMed]
  5. S. Sathish, R. W. Martin, and T. J. Moran, "Local surface skimming longitudinal wave velocity and residual stress mapping," J. Acoust. Soc. Am. 115, 165-171 (2004).
    [CrossRef] [PubMed]
  6. M. Clark, S. D. Sharples, and M. Somekh, "Laser ultrasonic microscopy," Materials Evaluation 60, 1094-1098 (2002).
  7. S. D. Sharples, M. Clark, and M. G. Somekh, "All-optical adaptive scanning acoustic microscope," Ultrasonics 41, 295-299 (2003).
    [CrossRef] [PubMed]
  8. Y. Hong, S. D. Sharples, M. Clark, and M. G. Somekh, "Rapid measurement of surface acoustic wave velocity on single crystals using an all-optical adaptive scanning acoustic microscope," Appl. Phys. Lett. 83, 3260-3262 (2003).
    [CrossRef]

2004 (1)

S. Sathish, R. W. Martin, and T. J. Moran, "Local surface skimming longitudinal wave velocity and residual stress mapping," J. Acoust. Soc. Am. 115, 165-171 (2004).
[CrossRef] [PubMed]

2003 (2)

S. D. Sharples, M. Clark, and M. G. Somekh, "All-optical adaptive scanning acoustic microscope," Ultrasonics 41, 295-299 (2003).
[CrossRef] [PubMed]

Y. Hong, S. D. Sharples, M. Clark, and M. G. Somekh, "Rapid measurement of surface acoustic wave velocity on single crystals using an all-optical adaptive scanning acoustic microscope," Appl. Phys. Lett. 83, 3260-3262 (2003).
[CrossRef]

2002 (2)

M. Clark, S. D. Sharples, and M. Somekh, "Laser ultrasonic microscopy," Materials Evaluation 60, 1094-1098 (2002).

S. Sathish and R. W. Martin, "Quantitative imaging of Rayleigh wave velocity with a scanning acoustic microscope," IEEE Trans. Ultrason. Ferroelectr. Freq. Control 49, 550-557 (2002).
[CrossRef] [PubMed]

1985 (1)

C. F. Quate, "Acoustic microscopy: recollections," IEEE Trans. Sonics Ultrason. SU-32, 132 (1985).
[CrossRef]

Clark, M.

S. D. Sharples, M. Clark, and M. G. Somekh, "All-optical adaptive scanning acoustic microscope," Ultrasonics 41, 295-299 (2003).
[CrossRef] [PubMed]

Y. Hong, S. D. Sharples, M. Clark, and M. G. Somekh, "Rapid measurement of surface acoustic wave velocity on single crystals using an all-optical adaptive scanning acoustic microscope," Appl. Phys. Lett. 83, 3260-3262 (2003).
[CrossRef]

M. Clark, S. D. Sharples, and M. Somekh, "Laser ultrasonic microscopy," Materials Evaluation 60, 1094-1098 (2002).

Hong, Y.

Y. Hong, S. D. Sharples, M. Clark, and M. G. Somekh, "Rapid measurement of surface acoustic wave velocity on single crystals using an all-optical adaptive scanning acoustic microscope," Appl. Phys. Lett. 83, 3260-3262 (2003).
[CrossRef]

Martin, R. W.

S. Sathish, R. W. Martin, and T. J. Moran, "Local surface skimming longitudinal wave velocity and residual stress mapping," J. Acoust. Soc. Am. 115, 165-171 (2004).
[CrossRef] [PubMed]

S. Sathish and R. W. Martin, "Quantitative imaging of Rayleigh wave velocity with a scanning acoustic microscope," IEEE Trans. Ultrason. Ferroelectr. Freq. Control 49, 550-557 (2002).
[CrossRef] [PubMed]

Moran, T. J.

S. Sathish, R. W. Martin, and T. J. Moran, "Local surface skimming longitudinal wave velocity and residual stress mapping," J. Acoust. Soc. Am. 115, 165-171 (2004).
[CrossRef] [PubMed]

Quate, C. F.

C. F. Quate, "Acoustic microscopy: recollections," IEEE Trans. Sonics Ultrason. SU-32, 132 (1985).
[CrossRef]

Sathish, S.

S. Sathish, R. W. Martin, and T. J. Moran, "Local surface skimming longitudinal wave velocity and residual stress mapping," J. Acoust. Soc. Am. 115, 165-171 (2004).
[CrossRef] [PubMed]

S. Sathish and R. W. Martin, "Quantitative imaging of Rayleigh wave velocity with a scanning acoustic microscope," IEEE Trans. Ultrason. Ferroelectr. Freq. Control 49, 550-557 (2002).
[CrossRef] [PubMed]

Sharples, S. D.

Y. Hong, S. D. Sharples, M. Clark, and M. G. Somekh, "Rapid measurement of surface acoustic wave velocity on single crystals using an all-optical adaptive scanning acoustic microscope," Appl. Phys. Lett. 83, 3260-3262 (2003).
[CrossRef]

S. D. Sharples, M. Clark, and M. G. Somekh, "All-optical adaptive scanning acoustic microscope," Ultrasonics 41, 295-299 (2003).
[CrossRef] [PubMed]

M. Clark, S. D. Sharples, and M. Somekh, "Laser ultrasonic microscopy," Materials Evaluation 60, 1094-1098 (2002).

Somekh, M.

M. Clark, S. D. Sharples, and M. Somekh, "Laser ultrasonic microscopy," Materials Evaluation 60, 1094-1098 (2002).

Somekh, M. G.

Y. Hong, S. D. Sharples, M. Clark, and M. G. Somekh, "Rapid measurement of surface acoustic wave velocity on single crystals using an all-optical adaptive scanning acoustic microscope," Appl. Phys. Lett. 83, 3260-3262 (2003).
[CrossRef]

S. D. Sharples, M. Clark, and M. G. Somekh, "All-optical adaptive scanning acoustic microscope," Ultrasonics 41, 295-299 (2003).
[CrossRef] [PubMed]

Appl. Phys. Lett. (1)

Y. Hong, S. D. Sharples, M. Clark, and M. G. Somekh, "Rapid measurement of surface acoustic wave velocity on single crystals using an all-optical adaptive scanning acoustic microscope," Appl. Phys. Lett. 83, 3260-3262 (2003).
[CrossRef]

IEEE Trans. Sonics Ultrason. (1)

C. F. Quate, "Acoustic microscopy: recollections," IEEE Trans. Sonics Ultrason. SU-32, 132 (1985).
[CrossRef]

IEEE Trans. Ultrason. Ferroelectr. Freq. Control (1)

S. Sathish and R. W. Martin, "Quantitative imaging of Rayleigh wave velocity with a scanning acoustic microscope," IEEE Trans. Ultrason. Ferroelectr. Freq. Control 49, 550-557 (2002).
[CrossRef] [PubMed]

J. Acoust. Soc. Am. (1)

S. Sathish, R. W. Martin, and T. J. Moran, "Local surface skimming longitudinal wave velocity and residual stress mapping," J. Acoust. Soc. Am. 115, 165-171 (2004).
[CrossRef] [PubMed]

Materials Evaluation (1)

M. Clark, S. D. Sharples, and M. Somekh, "Laser ultrasonic microscopy," Materials Evaluation 60, 1094-1098 (2002).

Ultrasonics (1)

S. D. Sharples, M. Clark, and M. G. Somekh, "All-optical adaptive scanning acoustic microscope," Ultrasonics 41, 295-299 (2003).
[CrossRef] [PubMed]

Other (2)

R. S. Gilmore, Ultrasonic Instruments and Devices II, vol. 24 of Physical Acoustics, chap. 5, pp. 275-346 (Academic Press, San Diego, CA, USA, 1999). (Editors: R N Thurston and Allan D Pierce).

M. G. Somekh, G. A. D. Briggs, and C. Ilett, "The effect of elastic-anisotropy on contrast in the scanning acoustic microscope," Philosophical magazine A-Physics of condensed matter structure defects and mechanical properties 49, 179-204 (1984).
[CrossRef]

Supplementary Material (2)

» Media 1: MOV (2158 KB)     
» Media 2: MOV (9889 KB)     

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Figures (5)

Fig. 1.
Fig. 1.

The graph shows how the amplitude of the detected surface acoustic waves varies with respect to the fringe spacing of the pattern used to generate the SAWs. The solid line represents experimental data, and the dashed line represents a Gaussian curve fitted to the data.

Fig. 2.
Fig. 2.

(2.2 MB) This video shows the process of builing up a velocity map of a material by calculating the peak amplitude for each point on the material surface. The calculated SAW velocity corresponds to the area under the grating, rather than the point of detection. (9.7 MB version)

Fig. 3.
Fig. 3.

Schematic of the experimental system.

Fig. 4.
Fig. 4.

The main image (to the left) is a velocity map of a 45×45mm area of a Ti-6246 alloy. The color scale indicates the phase velocity of the SAWs horizontally across the image. The sub-image is of a similar area, but at a lower spatial and velocity resolution, and was acquired in around 10 minutes.

Fig. 5.
Fig. 5.

A 48×33mm velocity map of Ti-6246. The contrast in the SAW velocity indicates large grains.

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