Attenuation characteristics of low frequency longitudinal guided waves generated by magnetostrictive transducers in bridge cables

2022 ◽  
Vol 164 ◽  
pp. 108296
Author(s):  
Xin Chen ◽  
Jinsong Zhu ◽  
Yangzi Lin
2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Peng Guo ◽  
Bo Deng ◽  
Xiang Lan ◽  
Kaili Zhang ◽  
Hongyuan Li ◽  
...  

This paper presents a water level sensing method using guided waves of A0 and quasi-Scholte modes. Theoretical, numerical, and experimental studies are performed to investigate the properties of both the A0 and quasi-Scholte modes. The comparative study of dispersion curves reveals that the plate with one side in water supports a quasi-Scholte mode besides Lamb modes. In addition, group velocities of A0 and quasi-Scholte modes are different. It is also found that the low-frequency A0 mode propagating in a free plate can convert to the quasi-Scholte mode when the plate has one side in water. Based on the velocity difference and mode conversion, a water level sensing method is developed. For the proof of concept, a laboratory experiment using a pitch-catch configuration with two piezoelectric transducers is designed for sensing water level in a steel vessel. The experimental results show that the travelling time between the two transducers linearly increases with the increase of water level and agree well with the theoretical predictions.


Electronics ◽  
2019 ◽  
Vol 8 (3) ◽  
pp. 315 ◽  
Author(s):  
Kumar Anubhav Tiwari ◽  
Renaldas Raisutis ◽  
Olgirdas Tumsys ◽  
Armantas Ostreika ◽  
Kestutis Jankauskas ◽  
...  

The estimation of the size and location of defects in multi-layered composite structures by ultrasonic non-destructive testing using guided waves has attracted the attention of researchers for the last few decades. Although extensive signal processing techniques are available, there are only a few studies available based on image processing of the ultrasonic B-scan image to extract the size and location of defects via the process of ultrasonic non-destructive testing. This work presents an image processing technique for ultrasonic B-scan images to improve the estimation of the location and size of disbond-type defects in glass fiber-reinforced plastic materials with 25-mm and 51-mm diameters. The sample is a segment of a wind turbine blade with a variable thickness ranging from 3 to 24 mm. The experiment is performed by using a low-frequency ultrasonic system and a pair of contact-type piezoceramic transducers kept apart by a 50-mm distance and embedded on a moving mechanical panel. The B-scan image acquired by the ultrasonic pitch-catch technique is denoised by utilizing features of two-dimensional discrete wavelet transform. Thereafter, the normalized pixel densities are compared along the scanned distance on the region of interest of the image, and a −3 dB threshold is applied to the locations and sizes the defects in the spatial domain.


1999 ◽  
Vol 09 (05) ◽  
pp. 755-798 ◽  
Author(s):  
A. S. BONNET-BEN DHIA ◽  
J. DUTERTE ◽  
P. JOLY

We present here a theoretical study of the guided waves in an isotropic homogeneous elastic half-space whose free surface has been deformed. The deformation is supposed to be invariant in the propagation direction and localized in the transverse ones. We show that finding guided waves amounts to solving a family of 2-D eigenvalue problems set in the cross-section of the propagation medium. Then using the min-max principle for non-compact self-adjoint operators, we prove the existence of guided waves for some particular geometries of the free surface. These waves have a smaller speed than that of the Rayleigh wave in the perfect half-space and a finite transverse energy. Moreover, we prove that the existence results are valid for arbitrary high frequencies in the presence of singularities of the free boundary. Finally, we prove that no guided mode can exist at low frequency, except maybe the fundamental one.


Geophysics ◽  
1989 ◽  
Vol 54 (12) ◽  
pp. 1596-1606 ◽  
Author(s):  
Ari Poikonen ◽  
Ilkka Suppala

Numerical models employed in ground VLF modeling use a normally incident (homogeneous) plane wave as a primary field. We show that these models are not directly applicable to modeling the impedance and wavetilt in the air, quantities needed in the interpretation of airborne VLF resistivity measurements. Instead, the primary field must be replaced by an inhomogeneous plane wave incident on the ground at an angle close to 90 degrees in order to provide the correct behavior of the apparent resistivities in the air. VLF magnetic polarization parameters, however, can be modeled in the air using the normally incident plane wave as a primary field. We also show that the plane‐wave analysis provides the same attenuation characteristics for the wavetilt in the air that is predicted by the Norton’s surface wave obtained by using the vertical electric dipole as a source. Use of the inhomogeneous plane wave introduces the vertical component of the electric field in the model. A 2‐D modeling technique based on the network solution is used to demonstrate the effects of the vertical electric field in the H‐polarization case. The vertical electric field generates charge distributions on the horizontal boundaries of conductors. In the case of a vertical sheet‐like conductor, these charges cause a slight asymmetry in apparent‐resistivity anomalies. Attenuation characteristics of various VLF anomalies with altitude are also presented. The H‐polarization anomalies attenuate much more rapidly in the air than those for E‐polarization due to the difference in the dominating source of EM fields in each polarization.


2015 ◽  
Vol 137 (6) ◽  
pp. 3253-3262 ◽  
Author(s):  
Roson Kumar Pattanayak ◽  
Prabhakaran Manogharan ◽  
Krishnan Balasubramaniam ◽  
Prabhu Rajagopal
Keyword(s):  

Geophysics ◽  
1988 ◽  
Vol 53 (6) ◽  
pp. 807-823 ◽  
Author(s):  
Denis P. Schmitt ◽  
Michel Bouchon ◽  
Guy Bonnet

The wave field generated by a point source in an axisymmetric fluid‐filled borehole embedded in a saturated porous formation is studied in both the spectral domain and time domain. The formation is modeled following Biot theory modified in accordance with homogenization theory. When the borehole wall is permeable, guided waves can be significantly affected by the permeability of the formation. Whatever the formation, fast or slow, Stoneley‐wave phase velocity and energy decrease and attenuation (in the sense of [Formula: see text]) increases with increasing permeability. These effects are more important in the very low‐frequency range, where Darcy’s law governs the fluid motion and the wave energy at the interface is maximum, than at higher frequencies. The effects increase and persist over a larger frequency range with decreasing viscosity and increasing compressibility of the saturant fluid, with increasing pore‐fluid volume, and with decreasing borehole radius. In contrast, the effects decrease with decreasing stiffness of the formation because of more efficient coupling of the interface wave to the surrounding medium. When present, the first pseudo‐Rayleigh mode also carries useful information. Fluid flow affects only the attenuation of the pseudo‐Rayleigh mode’s Airy phase; an increase in attenuation may be used to detect permeable zones and to infer the saturant fluid properties. However, the most reliable types of information are the formation shear‐wave velocity and attenuation from the low‐frequency part of the mode. In the time domain, all the modes overlap. Any signal processing should then be performed in the frequency domain, where mode spectra are more easily separable. The frequency band of the actual logging tool has to be large enough to ensure significant amplitude for each mode. Finally, the larger the number of receivers and the offset range, the better.


Sensors ◽  
2018 ◽  
Vol 18 (7) ◽  
pp. 2122 ◽  
Author(s):  
Habiba Lais ◽  
Premesh S. Lowe ◽  
Tat-Hean Gan ◽  
Luiz C. Wrobel ◽  
Jamil Kanfoud

Sign in / Sign up

Export Citation Format

Share Document