scholarly journals Piezoelectric Electro-Mechanical Impedance (EMI) Based Structural Crack Monitoring

2020 ◽  
Vol 10 (13) ◽  
pp. 4648 ◽  
Author(s):  
Tao Wang ◽  
Bohai Tan ◽  
Mingge Lu ◽  
Zheng Zhang ◽  
Guangtao Lu
Keyword(s):  
Resonance Frequency ◽  
Signal To Noise Ratio ◽  
Mechanical Impedance ◽  
Peak Frequency ◽  
Crack Size ◽  
Impedance Method ◽  
Small Scale ◽  
Element Simulation ◽  
Piezoelectric Impedance ◽  
Good Repeatability

To detect small cracks in plate like structures, the high frequency characteristics of local dynamics were studied with the piezoelectric electro-mechanical impedance (EMI) method, and damages were monitored by the changes of the EMI. The finite element simulation model of EMI was established, and numerical analysis was conducted. The simulation results indicated that the peak frequency of the piezoelectric admittance signal is a certain order resonance frequency of the structure, and the piezoelectric impedance method could effectively detect the dynamic characteristics of the structure. The piezoelectric admittance simulation and experimental study of aluminum beams with different crack sizes were performed. Simulation and experimental results revealed that the peak admittance frequency decreases with the increase of crack size, and the higher resonance frequency is more sensitive to the small-scale damage. The proposed method has good repeatability and strong signal-to-noise ratio to monitor the occurrence and development of small-scale crack damage, and it has an important application prospect.

A PZT-based electromechanical impedance method for monitoring the moisture content of wood

Sensor Review ◽  
2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Quan Zhai ◽  
Jicheng Zhang ◽  
Guofeng Du ◽  
Yulong Rao ◽  
Xiaoyu Liu
Keyword(s):  
Moisture Content ◽  
Mechanical Impedance ◽  
Impedance Method ◽  
Impedance Change ◽  
Monitoring Method ◽  
Content Type ◽  
Electromechanical Impedance ◽  
Wide Range ◽  
Impedance Technique ◽  
Piezoelectric Impedance

Purpose At present, piezoelectric impedance technology has been used in the study of wood damage monitoring. However, little effort has been made in the research on the application of piezoelectric impedance system to monitor the change of wood moisture content (MC). The monitoring method of wood MC is used by piezoelectric impedance technique in this study. Design/methodology/approach One piezoceramic transducer is bonded to the surface of wood specimens. The MC of the wood specimens increases gradually from 0% to 60% with 10% increments; the mechanical impedance of the wood specimen will change, and the change in the mechanical impedance of the structure is reflected by monitoring the change in the electrical impedance of lead zirconate titanate. Therefore, this paper investigates the relationship between wood MC change and piezoelectric impedance change to verify the feasibility of the piezoelectric impedance method for monitoring wood MC change. Findings The experiment verified that the real part of impedance of the wood increased with the increase of wood MC. Besides, the damage index root mean square deviation is introduced to quantify the damage degree of wood under different MC. At the same time, the feasibility and validity of this experiment were verified from the side by finite element simulation. Finally, MC monitoring by piezoelectric impedance technique is feasible. Originality/value To the best of the authors’ knowledge, this work is the first to apply piezoelectric ceramics to the monitoring of wood MC, which provides a theoretical basis for the follow-up study of a wide range of wood components and even wood structure MC changes.

The Study on Mechanical Impedance and Piezoelectric Impedance for Cantilever Beam Based on FEA Method

2011 ◽  
Vol 368-373 ◽  
pp. 1346-1350
Author(s):  
Jun Zhang ◽  
Qin Gao ◽  
Jian Zhong Wu ◽  
Juan Tao
Keyword(s):  
Resonance Frequency ◽  
Cantilever Beam ◽  
Damage Identification ◽  
Response Spectrum ◽  
Mechanical Impedance ◽  
Impedance Change ◽  
Resonance Modes ◽  
Impedance Response ◽  
Piezoelectric Coupling ◽  
Piezoelectric Impedance

The mechanical impedance and the piezoelectric coupling impedance response spectrum, the resonant vibration mode and he resonance frequency of the cantilever beam was analyzed by means of FEA for getting the relationship between mechanical impedance and piezoelectric impedance. The results showed that: Through the comparison between the two, both resonance frequency and resonance modes are the same basically, which also showed that the change of piezoelectric impedance changes with the mechanical impedance change. Piezoelectric impedance is the electric reflection of mechanical impedance. It provides a sound theoretical basis and research methods for the piezoelectric impedance damage identification and health monitoring technology.

scholarly journals Metal rings and discs Matlab/Simulink 3D model for ultrasonic sandwich transducer design

2012 ◽  
Vol 44 (3) ◽  
pp. 287-298 ◽  
Author(s):  
I. Jovanovic ◽  
D. Mancic ◽  
V. Paunovic ◽  
M. Radmanovic ◽  
V.V. Mitic
Keyword(s):  
Resonance Frequency ◽  
3D Model ◽  
Mechanical Impedance ◽  
Analytical Models ◽  
Resonant Frequencies ◽  
Matlab Simulink ◽  
Simulink Model ◽  
Metal Rings ◽  
Resonant Modes ◽  
Transducer Design

Metal-endings are integral part of different ultrasonic sandwich transducers. In this paper a new Matlab/Simulink 3D model of the finite metal rings and discs of various dimensions is realized. With this model, which describes both the thickness and the radial resonant modes, and the coupling between them, mechanical impedance of the sample can be easily computed. Resonance frequency-length curves for rings and disks with various materials and for different selected dimensions are given. Also, comparisons of the different approaches in determining of their resonant frequencies are shown. The proposed Matlab/Simulink model requires simpler implementation than other analytical models. That enabled modifying of 1D theory and simplified modelling and projecting of the ultrasonic sandwich transducers with short-endings. Finally, the computed and experimental results are compared.

The Relationship of Normal and Abnormal Microstructural Proliferation to the Mitral Valve Closure Sound

2005 ◽  
Vol 127 (1) ◽  
pp. 134-147 ◽  
Author(s):  
Daniel R. Einstein ◽  
Karyn S. Kunzelman ◽  
Per G. Reinhall ◽  
Mark A. Nicosia ◽  
Richard P. Cochran
Keyword(s):  
Mitral Valve ◽  
Volume Fraction ◽  
Contrast Material ◽  
Element Model ◽  
Peak Frequency ◽  
Material Behavior ◽  
Small Scale ◽  
Valve Closure ◽  
Valvular Function ◽  
The Relationship

Background : Many diseases that affect the mitral valve are accompanied by the proliferation or degradation of tissue microstructure. The early acoustic detection of these changes may lead to the better management of mitral valve disease. In this study, we examine the nonstationary acoustic effects of perturbing material parameters that characterize mitral valve tissue in terms of its microstructural components. Specifically, we examine the influence of the volume fraction, stiffness and splay of collagen fibers as well as the stiffness of the nonlinear matrix in which they are embedded. Methods and Results: To model the transient vibrations of the mitral valve apparatus bathed in a blood medium, we have constructed a dynamic nonlinear fluid-coupled finite element model of the valve leaflets and chordae tendinae. The material behavior for the leaflets is based on an experimentally derived structural constitutive equation. The gross movement and small-scale acoustic vibrations of the valvular structures result from the application of physiologic pressure loads. Material changes that preserved the anisotropy of the valve leaflets were found to preserve valvular function. By contrast, material changes that altered the anisotropy of the valve were found to profoundly alter valvular function. These changes were manifest in the acoustic signatures of the valve closure sounds. Abnormally, stiffened valves closed more slowly and were accompanied by lower peak frequencies. Conclusion: The relationship between stiffness and frequency, though never documented in a native mitral valve, has been an axiom of heart sounds research. We find that the relationship is more subtle and that increases in stiffness may lead to either increases or decreases in peak frequency depending on their relationship to valvular function.

Assessment of GRACE-FO Laser Ranging Interferometer measurements

2021 ◽  
Author(s):  
Athina Peidou ◽  
Felix Landerer ◽  
David Wiese ◽  
Matthias Ellmer ◽  
Eugene Fahnestock ◽  
...  
Keyword(s):  
High Frequency ◽  
Signal To Noise Ratio ◽  
Small Scale ◽  
Laser Ranging ◽  
High Signal ◽  
Measurement Sensitivity ◽  
One Year ◽  
Mass Transfers ◽  
Gravity Recovery ◽  
System Errors

<p>The performance of Gravity Recovery and Climate Experiment Follow‐On (GRACE-FO) laser ranging interferometer (LRI) system is assessed in both space and frequency domains. With LRI’s measurement sensitivity being as small as 0.05 nm/s<sup>2</sup> at GRACE-FO altitude we perform a thorough assessment on the ability of the instrument to detect real small-scale high-frequency gravity signals. Analysis of range acceleration measurements along the orbit for nearly one year of daily solutions suggests that LRI can detect signals induced by mass perturbation up to 26 mHz, i.e., ~145 km spatial resolution. Additionally, high frequency signals that are not adequately modeled by dealiasing models are clearly detected and their magnitude is shown to reach 2-3 nm/s<sup>2</sup>. The alternative K‐band microwave ranging system (KBR) is also examined and results demonstrate the inability of KBR to retrieve signals above 15mHz (i.e., shorter than ~200 km) as the noise of the KBR range acceleration increases rapidly. Overall, the first stream of LRI measurements shows that the high signal to noise ratio allows for detection of mass transfers in finer scales, however the ability to fully exploit the high-quality signal measured by the LRI in Level 2 products is still constrained by noise of background models and other onboard instrumentation and measurement system errors.</p><p>Copyright Acknowledgment: This work was performed at the California Institute of Technology's Jet Propulsion Laboratory under a contract with the National Aeronautics and Space Administration's Cryosphere Science Program.</p>

scholarly journals Using Hilbert Transform in Diagnostic of Composite Materials by Impedance Method

2020 ◽  
Vol 64 (4) ◽  
pp. 334-342 ◽  
Author(s):  
Volodymyr Eremenko ◽  
Artur Zaporozhets ◽  
Vitalii Babak ◽  
Volodymyr Isaienko ◽  
Kateryna Babikova
Keyword(s):  
Composite Materials ◽  
Nondestructive Testing ◽  
Hilbert Transform ◽  
Instantaneous Frequency ◽  
Information Quality ◽  
Low Frequency ◽  
Mechanical Impedance ◽  
Phase Characteristic ◽  
Impedance Method ◽  
Materials Testing

The article is devoted to the problem of the increasing of information quality for the impedance method of nondestructive testing. The purpose of this article is to get for the pulsed impedance method of nondestructive testing the additional informative parameters. Instantaneous values of the information signal's amplitude is a sensitive parameter to the effects of interference, in particular friction, which necessitates the use of additional informative features. It was experimentally measured signals from defective and defectless areas of the test pattern. Using of the Hilbert transform gave possibility to determine phase characteristics of these signals and realize demodulation to extract a low-frequency envelope for further analysis of its shape. It was received the informative features as a result of researches. Among them are instantaneous frequency of a signal, the integral of a phase characteristic on the selected interval and the integral of a difference signal phase characteristics. In order to compare quality of the defect detection using selected parameters it was carried out evaluation of the testing result reliability for a product fragment made of a composite material. Considering the influence of the change in the mechanical impedance of the researched area on the phase-frequency characteristics of the output signal of the converter, it is proposed to use as the diagnostic signs: the instantaneous frequency and the value of the phase characteristic of the current signal for certain points in time. The proposed informative features enable to increase general reliability of composite materials testing by the pulsed impedance method.

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