Event Title

Recovering of Phase Velocities Through Anisotropic Plates by a Direct Summation of Signals Generated by Line Sources

Location

Snowbird, UT, USA

Start Date

1-1-1999 12:00 AM

Description

The LASER ultrasonic technique is a powerful mean to generate and detect ultrasonic waves at a distance, without any contact to the specimen. However, it is now well known that in anisotropic media, acoustic waves generated by a line or point source propagate at group velocities which are different from the phase ones. The recovering of phase velocities from such generated acoustic waves is a non trivial matter that requires a numerical analysis [1, 2] of a set of measured group velocities. An alternative solution is proposed: the signal such as it is generated by a plane wave refracted through an anisotropic plate is numerically built. For that purpose, a set of signals are recorded by scanning the line source in a direction normal to it with a constant step. Each measured signal is then shift in time with a constant delay. The summation of the obtained signals yields a waveform similar to the one recorded when a plane wave is refracted through the material. The phase velocity can thus be easily obtained in various directions of propagation.

Book Title

Review of Progress in Quantitative Nondestructive Evaluation

Volume

18A

Chapter

Chapter 1: Elastic Waves and Ultrasonic Techniques

Section

Laser Ultrasonics and Applications

Pages

325-332

DOI

10.1007/978-1-4615-4791-4_40

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Recovering of Phase Velocities Through Anisotropic Plates by a Direct Summation of Signals Generated by Line Sources

Snowbird, UT, USA

The LASER ultrasonic technique is a powerful mean to generate and detect ultrasonic waves at a distance, without any contact to the specimen. However, it is now well known that in anisotropic media, acoustic waves generated by a line or point source propagate at group velocities which are different from the phase ones. The recovering of phase velocities from such generated acoustic waves is a non trivial matter that requires a numerical analysis [1, 2] of a set of measured group velocities. An alternative solution is proposed: the signal such as it is generated by a plane wave refracted through an anisotropic plate is numerically built. For that purpose, a set of signals are recorded by scanning the line source in a direction normal to it with a constant step. Each measured signal is then shift in time with a constant delay. The summation of the obtained signals yields a waveform similar to the one recorded when a plane wave is refracted through the material. The phase velocity can thus be easily obtained in various directions of propagation.