scholarly journals Lamb waves in the wavenumber-time domain: Separation of established and non-established regimes

Wave Motion ◽  
2021 ◽  
pp. 102736
Author(s):  
Pierric Mora
Keyword(s):  
Time Domain ◽  
Lamb Waves ◽  
Domain Separation

A generalized tool for accurate time-domain separation of excited modes in spin-torque oscillators

2014 ◽  
Vol 115 (17) ◽  
pp. 17D108 ◽  
Author(s):  
Giulio Siracusano ◽  
Aurelio La Corte ◽  
Vito Puliafito ◽  
Giovanni Finocchio
Keyword(s):  
Time Domain ◽  
Spin Torque ◽  
Domain Separation ◽  
Spin Torque Oscillators

Active Scour Monitoring using Ultrasonic Time Domain Reflectometry of Buried Slender Sensors

2021 ◽  
Author(s):  
Morgan Funderburk ◽  
Jamie Tran ◽  
Michael Todd ◽  
Anton Netchaev ◽  
Kenneth J Loh
Keyword(s):  
Time Domain ◽  
Extreme Event ◽  
Lamb Waves ◽  
The United States ◽  
External Pressure ◽  
Time Domain Reflectometry ◽  
Scour Monitoring ◽  
Ultrasonic Time ◽  
Bridge Failure ◽  
Soil Interface

Abstract Local scour is a growing cause of bridge failure in the United States and around the world. In the next century, the effects of climate changes will make more bridges susceptible to scour failure more than ever before. This study aims to harness the spatially continuous monitoring capabilities of ultrasonic time-domain reflectometry to detect a soil interface for the purposes of scour monitoring. In this study, a long, slender plate is coupled with two flexible piezoelectric devices that propagate Lamb waves along the length of the plate to form the scour sensor. The sensor was tested for sensitivity to external pressure using metal weights, and was able to detect the position of the pressure up at a length of up to ~ 20 feet. The sensor was tested under simulated scour conditions, being buried in sand at various depths. The results show that the Lamb wave scour sensor is capable of reliably detecting a soil interface at 1 ft intervals. The scour sensor was also able to detect uncompacted soil interfaces, which is important considering the issue of scour hole refill following an extreme event.

Time-domain topological energy imaging with ultrasonic Lamb waves considering multiple defects

2020 ◽  
Vol 62 (4) ◽  
pp. 208-215
Author(s):  
Wenfa Zhu ◽  
Yujie Zhang ◽  
Guopeng Fan ◽  
Haiyan Zhang ◽  
Shao Wei
Keyword(s):  
Numerical Simulation ◽  
Time Domain ◽  
Lamb Waves ◽  
Super Resolution ◽  
Element Model ◽  
Rayleigh Criterion ◽  
Multiple Defects ◽  
Reference Medium ◽  
Resolution Imaging ◽  
Imaging Resolution

This study presents a fast imaging approach with ultrasonic Lamb waves based on time-domain topological energy to identify multiple defects with defect spacing smaller than the threshold of the Rayleigh criterion in terms of imaging resolution. The direct acoustical field and time-domain topological energy of the two fields are used as imaging functions when considering the calculation of direct and adjoint acoustical fields in a non-defective reference medium on the basis of topological theory. The functions are not limited by acoustic diffraction and can achieve super-resolution imaging with multiple defects. First, a 3D finite element model is established. Transient acoustic field diagrams at different moments are used to show the focusing process of direct and adjoint acoustical fields clearly with multiple defects, thereby revealing the physical mechanism of time-domain topological energy imaging. Second, the effectiveness of the proposed approach to characterise multiple defects when the defect spacing is smaller than the imaging resolution threshold is verified through numerical simulation. Finally, the feasibility of super-resolution imaging considering multiple defects is proven by conducting experiments on aluminium plate samples with multiple defects under different defect spacing conditions. Numerical simulation and experimental results show that the proposed approach can overcome the problem of multiple defects with defect spacing smaller than the imaging resolution threshold by breaking the Rayleigh criterion constraint, while the accuracy presented is higher than that of the traditional delay-and-sum method.

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