Scholte wave generation by vertically guided waves in steep topographic feature

Ultrasonic guided waves provide unique capabilities for the structural health monitoring of plate-like structures. They can detect and locate various types of material degradation through the interaction of shear-horizontal (SH) waves and Lamb waves with the material. Magnetostrictive transducers (MSTs) can be used to generate and receive both SH and Lamb waves and yet their characteristics have not been thoroughly studied, certainly not on par with piezoelectric transducers. A series of multiphysics simulations of the MST/plate system is conducted to investigate the characteristics of MSTs that affect guided wave generation and reception. The results are presented in the vein of showing the flexibility that MSTs provide for guided waves in a diverse range of applications. In addition to studying characteristics of the MST components (i.e., the magnetostrictive layer, meander electric coil, and biased magnetic field), single-sided and double-sided MSTs are compared for preferential wave mode generation. The wave mode control principle is based on the activation line for phase velocity dispersion curves, whose slope is the wavelength, which is dictated by the meander coil spacing. A double-sided MST with in-phase signals preferentially excites symmetric SH and Lamb modes, while a double-sided MST with out-of-phase signals preferentially excites antisymmetric SH and Lamb modes. All attempted single-mode actuations with double-sided MSTs were successful, with the SH3 mode actuated at 922 kHz in a 6-mm-thick plate being the highest frequency. Additionally, the results show that increasing the number of turns in the meander coil enhances the sensitivity of the MST as a receiver and substantially reduces the frequency bandwidth.

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Evaluation of Hidden Corrosion in a Thin Plate Using a Non-Contact Guided Wave Technique

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.321-323.492 ◽

2006 ◽

Vol 321-323 ◽

pp. 492-496 ◽

Cited By ~ 5

Author(s):

Ik Keun Park ◽

Tae Hyung Kim ◽

Hyun Mook Kim ◽

Yong Kwon Kim ◽

Yong Sang Cho ◽

...

Keyword(s):

Ultrasonic Wave ◽

Thin Plate ◽

Guided Waves ◽

Wave Generation ◽

Guided Wave ◽

Thickness Reduction ◽

Thin Plates ◽

Depth Measurement ◽

Mode Cutoff ◽

Hidden Corrosion

In this paper, study on evaluation of thickness reduction in a thin plate with guided waves is presented. Ultrasonic guided wave techniques have been widely studied and successfully applied to various non-destructive tests with the advantage of long range inspection. In addition to application of guided waves to NDT, non-contact methods for ultrasonic wave generation and detection have become very useful and well combined with guided wave techniques due to their capability of ultrasonic wave generation and reception in surface of high temperature or on rough surface. An advanced non-contact technique for detection of thickness reduction simulating hidden corrosion in thin plates using guided waves is proposed. The proposed approach uses EMAT(Electro-Magnetic Acoustic Transducer) for the non-contact generation and detection of guided waves in aluminum plates. Interesting features of the dispersive behavior in selected wave modes are used to detect plate thinning. The experimental results show that the mode cutoff measurements provide a qualitative measurement of thinning detects and change in the mode group velocity can be used as quantitative parameter of thinning depth measurement.

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Very low‐frequency seismic noise in shallow water: Scholte wave generation and propagation at two offshore sites

10.1190/1.1891944 ◽

1987 ◽

Cited By ~ 1

Author(s):

Hassan B. Ali ◽

Gerard J. Tango ◽

Michael F. Werby

Keyword(s):

Shallow Water ◽

Seismic Noise ◽

Low Frequency ◽

Wave Generation ◽

Very Low Frequency ◽

Scholte Wave

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Evanescent Schölte waves of arbitrary profile and direction

European Journal of Applied Mathematics ◽

10.1017/s0956792511000362 ◽

2011 ◽

Vol 23 (2) ◽

pp. 267-287 ◽

Cited By ~ 11

Author(s):

D. F. PARKER

Keyword(s):

Harmonic Function ◽

Half Space ◽

Guided Waves ◽

Elastic Half Space ◽

Normal Displacement ◽

Compact Representation ◽

Arbitrary Boundary ◽

Scholte Waves ◽

Scholte Wave ◽

Complex Valued

Schölte waves, waves bound to the interface between a fluid and an elastic half-space, are, for many material combinations, evanescent; as they propagate, they are damped due to radiation. A representation of the general evanescent Schölte wave is here obtained in terms of a solution to the membrane equation with complex speed, linked, at each instant, to a complex-valued harmonic function in a half-space. This derivation generalises one obtained recently for (non-evanescent) Rayleigh, Stoneley and Schölte waves. An alternative description is also obtained, in which the time-evolution of the normal displacement of the interface satisfies a first-order, complex-valued, non-local evolution equation. Amongst some explicit solutions obtained are decaying solutions allied to a general solution to the Helmholtz equation, and a solution closely related to a Gaussian beam. In the plane–strain case, the general Schölte wave splits into two disturbances, one right-travelling and one left-travelling, each being described at all times in terms of a harmonic function in a half-plane, decaying with depth yet having arbitrary boundary values. This representation highlights the dual elliptic–hyperbolic nature typical of guided waves and gives a surprisingly compact representation for the two-dimensional case.

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