Imaging of Lamb Waves in Plates for Quantitative Determination of Anisotropy using Photorefractive Dynamic Holography

Conference · Mon Jun 01 00:00:00 EDT 1998

DOI:https://doi.org/10.1007/978-1-4615-4791-4_128· OSTI ID:910875

Telschow, Kenneth Louis; Deason, Vance Albert; Schley, Robert Scott; Watson, Scott Marshall

Anisotropic properties of sheet materials can be determined by measuring the propagation of Lamb waves in different directions. Electromagnetic acoustic transduction and laser ultrasonic methods provide noncontacting approaches that are often desired for application to industrial and processing environments. This paper describes a laser imaging approach utilizing the adaptive property of photorefractive materials to produce a real-time measurement of the antisymmetric Lamb wave mode in all directions simultaneously. Continuous excitation is employed enabling the data to be recorded and displayed by a CCD camera. Analysis of the image produces a direct quantitative determination of the phase velocity in all directions showing plate anisotropy in the plane. Many optical techniques for measuring ultrasonic motion at surfaces have been developed for use in applications such as vibration measurement and laser ultrasonics. Most of these methods have similar sensitivities and are based on time domain processing using homodyne, Fabry-Perot [1], and, more recently, photorefractive interferometry [2]. Generally, the methods described above do not allow measurement at more than one surface point simultaneously, requiring multiple beam movements and scanning in order to produce images of surface ultrasonic motion over a large area. Electronic speckle interferometry, including shearography, does provide images directly of vibrations over large surface areas. This method has proven very durable in the field for large displacement amplitudes of several wavelengths. In addition, a sensitivity of ë/3000 has been demonstrated under laboratory conditions [3]. Full-field imaging of traveling ultrasonic waves using digital shearography has been recently reported with sensitivity in the nanometer range [4]. With this method, optical interference occurs at the photodetector

• Research Organization: Idaho National Lab. (INL), Idaho Falls, ID (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: DE-AC07-99ID-13727
• OSTI ID: 910875
• Report Number(s): INEEL/CON-98-00338; TRN: US200802%%252
• Resource Relation: Conference: 25th Annual Review of Progress in Quantitative Nondestructive Examination,Snowbird, UT,06/19/1998,06/24/1998
• Country of Publication: United States
• Language: English

Related Subjects

99 - GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
ACOUSTICS
AMPLITUDES
ANISOTROPY
EXCITATION
HOLOGRAPHY
INTERFEROMETRY
LASERS
PHASE VELOCITY
PHOTODETECTORS
PLATES
PROCESSING
SENSITIVITY
ULTRASONIC WAVES
WAVELENGTHS
anisotropy
lamb waves
photorefractive dynamic holography