Green Functions for Cylindrical Elastic Waves in Aluminum: Comparison Between Theory and Experiments

1994 ◽  
Vol 61 (1) ◽  
pp. 219-221 ◽  
Author(s):  
A. Mourad ◽  
B. Castagne`de ◽  
E. Mottay
Keyword(s):  
Elastic Waves ◽  
Tangential Force ◽  
Ultrasonic Waves ◽  
Displacement Fields ◽  
Numerical Predictions ◽  
Elastic Thin Plate ◽  
Experimental Works ◽  
Laser Interferometric ◽  
Force Problem ◽  
Theory And Experiments

A comparison between experimental and theoretical displacement fields for the tangential force problem (which is a model of the thermoelastic regime for laser generated ultrasound) at an aluminum interface is reported. The numerical predictions are based on a standard formulation of the transient generation of elastic waves along a line source. In the configuration of a purely elastic thin plate, the cylindrical elastic waves are then detected on the other side by a point-like receiver. The experimental works is carried out with a pulsed Nd:YAG laser for the generation and a laser interferometric probe for the detection of ultrasonic waves.

scholarly journals Interferometric imaging of nonlocal electromechanical power transduction in ferroelectric domains

2018 ◽  
Vol 115 (21) ◽  
pp. 5338-5342 ◽  
Author(s):  
Lu Zheng ◽  
Hui Dong ◽  
Xiaoyu Wu ◽  
Yen-Lin Huang ◽  
Wenbo Wang ◽  
...  
Keyword(s):  
Electric Fields ◽  
Elastic Waves ◽  
Near Field ◽  
Nanoelectromechanical Systems ◽  
Nonlocal Interaction ◽  
Interferometric Imaging ◽  
Displacement Fields ◽  
Domain Structures ◽  
Acoustic Wave Devices ◽  
Electrical Generation

The electrical generation and detection of elastic waves are the foundation for acoustoelectronic and acoustooptic systems. For surface acoustic wave devices, microelectromechanical/nanoelectromechanical systems, and phononic crystals, tailoring the spatial variation of material properties such as piezoelectric and elastic tensors may bring significant improvements to the system performance. Due to the much slower speed of sound than speed of light in solids, it is desirable to study various electroacoustic behaviors at the mesoscopic length scale. In this work, we demonstrate the interferometric imaging of electromechanical power transduction in ferroelectric lithium niobate domain structures by microwave impedance microscopy. In sharp contrast to the traditional standing-wave patterns caused by the superposition of counterpropagating waves, the constructive and destructive fringes in microwave dissipation images exhibit an intriguing one-wavelength periodicity. We show that such unusual interference patterns, which are fundamentally different from the acoustic displacement fields, stem from the nonlocal interaction between electric fields and elastic waves. The results are corroborated by numerical simulations taking into account the sign reversal of piezoelectric tensor in oppositely polarized domains. Our work paves ways to probe nanoscale electroacoustic phenomena in complex structures by near-field electromagnetic imaging.

Forced Response of Interlocked Vane Segments: Numerical Predictions and Experimental Results

2006 ◽  
Author(s):  
Stefano Zucca ◽  
Sergio Filippi ◽  
Fabio Droetti ◽  
Muzio M. Gola
Keyword(s):  
Tangential Force ◽  
Harmonic Balance Method ◽  
Outer Radius ◽  
Forced Response ◽  
Experimental Results ◽  
Numerical Code ◽  
Friction Forces ◽  
Normal Contact ◽  
Numerical Predictions ◽  
Local Compliance

Resonant vibrations affect fatigue life of vane segments. Friction damping is employed to reduce vibration amplitude. When vane segments are assembled, they are twisted so that lower platforms are in contact. The sum of displacements of the two ends of the lower platform after twisting is defined ‘interlocking’. Different ‘interlocking’ values correspond to different values of normal contact force. When interlocked vanes vibrate under external force excitation, energy is dissipated by friction forces at lower platform contacts providing damping to the system. The aim of this paper is the experimental validation of a numerical code for forced response calculation of interlocked vane segments. Since friction forces depend on relative displacements of bodies in contact, the system is nonlinear. System force response is computed by means of Harmonic Balance Method (HBM). Contact model implemented in the code is characterised by tangential and normal stiffness to take into account local compliance of the contact area. Gross slip occurs when the instantaneous ratio of tangential force to normal force is equal to the friction coefficient. Also effect of microslip is taken in account. The experimental set-up used to validate the code is made of a vane segment fixed at the outer radius to an aluminium frame and in contact with two supports at the inner radius. Comparison between the numerical predictions and experimental results is performed for different values of interlocking (i.e. force normal to the contact).

Time reversal of ultrasonic waves in solids: Theory and experiments

1995 ◽  
Vol 98 (5) ◽  
pp. 2875-2875 ◽  
Author(s):  
Carsten Draeger ◽  
Didier Cassereau ◽  
Mathias Fink
Keyword(s):  
Time Reversal ◽  
Ultrasonic Waves ◽  
Theory And Experiments

Internal Structure Research of Shungite by Broadband Ultrasonic Spectroscopy

2017 ◽  
Vol 755 ◽  
pp. 242-247 ◽  
Author(s):  
Elena B. Cherepetskaya ◽  
Alexander A. Karabutov ◽  
Vladimir A. Makarov ◽  
Elena A. Mironova ◽  
Ivan A. Shibaev ◽  
...  
Keyword(s):  
Internal Structure ◽  
Wave Velocity ◽  
Elastic Waves ◽  
Elastic Moduli ◽  
Young Modulus ◽  
Ultrasonic Waves ◽  
Parallel Plates ◽  
Ultrasonic Spectroscopy ◽  
Accuracy Of Measurements ◽  
Structure Research

The internal structure of plane-parallel plates of shungite is studied. The broadband ultrasonic pulses are used to measure the velocities of longitudinal and shear elastic ultrasonic waves. The accuracy of measurements is 0.3% in the case of longitudinal wave velocity and 0.5% in the case of shear wave velocity (scanning pitch over the surface of specimens was 0.5 mm). Local elastic moduli of shungite (Young modulus, shear modulus and Poisson's ratio) are uniquely determined from the velocities of elastic waves.

Second Order Wave Generation Technique in the Laboratory

2007 ◽  
Author(s):  
M. H. Zaman ◽  
L. Mak
Keyword(s):  
Offshore Structures ◽  
Wave Generation ◽  
Second Order ◽  
Physical Model Test ◽  
Test Model ◽  
Generation Technique ◽  
Numerical Predictions ◽  
Wave Basin ◽  
Experimental Works ◽  
High Frequency Waves

Correct generation of the primary waves and the reproduction of the group-induced second-order low and high frequency waves have been considered essential for physical model test in the laboratory to understand the effects of the wave-action phenomena on, for instance, offshore structures, mooring system, LNG, other floating vessels, harbor resonance, etc. When natural waves are reproduced, the primary waves and their locked bounded waves are generated along with some unwanted free waves. Those free waves are evidently generated and propagate towards the test model and reflect from the boundaries. The free waves, having the same frequency of the bounded wave are reproduced due to mismatch of the boundary conditions at the wave paddle. The other two types of free waves are due to the wave paddle displacement and the local disturbances. The so-called second-order wave generation technique could eliminate these alleged free waves. In this experiment second-order wave generation technique is successfully used to reproduce the correct bounded waves along with elimination of the unwanted free waves from the wave profiles. This experiment is implemented by means of compensating free waves imposed on the system by second-order paddle motion. The control signal for this motion has to be introduced along with the primary waves. An extensive experimental works are carried out in the Offshore Engineering wave Basin (OEB) at the Institute of Ocean Technology (IOT), NRC to investigate the quality and the characteristics of the generated primary waves and their locked bounded waves when the unwanted free waves are eliminated. The measured results are then compared with the predicted results. Two different water depths are used within the shallow water limit. The obtained results are also compared with the numerical predictions.

PINNING OF A KINK IN A NONLINEAR DIFFUSIVE MEDIUM WITH A GEOMETRICAL BIFURCATION: THEORY AND EXPERIMENTS

2004 ◽  
Vol 14 (01) ◽  
pp. 257-262
Author(s):  
S. MORFU ◽  
P. MARQUIÉ ◽  
J. M. BILBAULT
Keyword(s):  
Bifurcation Theory ◽  
Coupling Conditions ◽  
Numerical Predictions ◽  
Diffusive Medium ◽  
Theory And Experiments

We study the dynamics of a kink propagating in a Nagumo chain presenting a geometrical bifurcation. In the case of weak couplings, we define analytically and numerically the coupling conditions leading to the pinning of the kink at the bifurcation site. Moreover, real experiments using a nonlinear electrical lattice confirm the theoretical and numerical predictions.

scholarly journals Directional Ultrasound Source for Solid Materials Inspection: Diffraction Management in a Metallic Phononic Crystal

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 6148
Author(s):  
Hossam Selim ◽  
Rubén Picó ◽  
Jose Trull ◽  
Miguel Delgado Prieto ◽  
Crina Cojocaru
Keyword(s):  
Elastic Waves ◽  
Phononic Crystal ◽  
Target Object ◽  
Ultrasonic Waves ◽  
Proof Of Concept ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
Focusing Effect ◽  
Waves Propagation ◽  
Non Destructive

In this work, we numerically investigate the diffraction management of longitudinal elastic waves propagating in a two-dimensional metallic phononic crystal. We demonstrate that this structure acts as an “ultrasonic lens”, providing self-collimation or focusing effect at a certain distance from the crystal output. We implement this directional propagation in the design of a coupling device capable to control the directivity or focusing of ultrasonic waves propagation inside a target object. These effects are robust over a broad frequency band and are preserved in the propagation through a coupling gel between the “ultrasonic lens” and the solid target. These results may find interesting industrial and medical applications, where the localization of the ultrasonic waves may be required at certain positions embedded in the object under study. An application example for non-destructive testing with improved results, after using the ultrasonic lens, is discussed as a proof of concept for the novelty and applicability of our numerical simulation study.

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