• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1273-1279
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• 2000

A new concept of piezoelectric smart panels for noise reduction in wide band frequencies is proposed and their possibility is experimentally investigated. The proposed panels are based on active and passive methods. They use piezoelectric smart structure technology for active noise reduction at low band frequencies and passive sound absorbing materials for mid-range of noise frequencies. To prove the concept of piezoelectric smart panels, an acoustic measurement experiment was performed. The smart panels exhibit a good noise reduction in middle and high frequency ranges due to the mass effects of absorbing materials or/and the air gap. The use of piezoelectric smart panel renders noise reduction large at resonance frequency. Another concept of smart panel that uses piezoelectric damping is experimentally investigated. Since piezoelectric dampings can reduce vibration and noise at resonance frequencies with simple shunt circuit, they have merits in terms of economy and simplicity. Dissipated energy method(DEM) is adopted to tune the shunt circuit precisely in piezoelectric dampings. Noise reduction at multiple resonance frequencies is demonstrated.

• Advances in nano research
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• 제9권3호
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• pp.193-210
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• 2020

In this research, beside presenting real images of produced Functionally Graded Carbon Nanotube-Reinforced Composites (FG-CNTRCs) and a brief review of the synthesis method of FG-CNTRCs, static and buckling analysis of FG-CNTRC with piezoelectric layers are investigated. It is assumed that the material properties of FG-CNTRC are varied through the thickness direction using four different distributions of Carbon Nanotubes (CNTs). To capture the size effects, nonlocal elasticity theory proposed by A.C. Eringen is also adopted in our model. One of the topics in our paper is using a higher order theory with eight different displacement fields and comparing their results with each other. To solve the governing equations, an analytical method is used to find the deflections and critical buckling loads of FG-CNTRCs. To show the accuracy of present methodology, our results are compared with the results of simply supported rectangular nano plates available in the literature. In this research, the effects of aspect ratio, piezoelectric layer and nonlocal parameter are also studied. It is hoped that this work leads to more accurate models on FG-CNTRC.

• Advances in nano research
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• 제14권6호
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• pp.575-590
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• 2023

Many of small-scale devices should be designed to tolerate high temperature changes. In the present study, the states of buckling and stability of nano-scale cylindrical shell structure integrated with piezoelectric layer under various thermal and electrical external loadings are scrutinized. In this regard, a multi-layer composite shell reinforced with graphene nano-platelets (GNP) having different patterns of layer configurations is modeled. An outer layer of piezoelectric material receiving external voltage is also attached to the cylindrical shell for the aim of observing the effects of voltage on the thermal buckling condition. The cylindrical shell is mathematically modeled with first-order shear deformation theory (FSDT). Linear elasticity relationship with constant thermal expansion coefficient is used to extract the relationship between stress and strain components. Moreover, minimum virtual work, including the work of the piezoelectric layer, is engaged to derive equations of motion. The derived equations are solved using numerical method to find out the effects of temperature and external voltage on the buckling stability of the shell structure. It is revealed that the boundary condition, external voltage and geometrical parameter of the shell structure have notable effects on the temperature rise required for initiating instability in the cylindrical shell structure.

• Advances in nano research
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• 제14권2호
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• pp.141-154
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• 2023

Effects of viscoelastic foundation on vibration of curved-beam structure with clamped and simply-supported boundary conditions is investigated in this study. In doing so, a micro-scale laminate composite beam with two piezoelectric face layer with a carbon nanotube reinforces composite core is considered. The whole beam structure is laid on a viscoelastic substrate which normally occurred in actual conditions. Due to small scale of the structure non-classical elasticity theory provided more accurate results. Therefore, nonlocal strain gradient theory is employed here to capture both nano-scale effects on carbon nanotubes and microscale effects because of overall scale of the structure. Equivalent homogenous properties of the composite core is obtained using Halpin-Tsai equation. The equations of motion is derived considering energy terms of the beam and variational principle in minimizing total energy. The boundary condition is assumed to be clamped at one end and simply supported at the other end. Due to nonlinear terms in the equations of motion, semi-analytical method of general differential quadrature method is engaged to solve the equations. In addition, due to complexity in developing and solving equations of motion of arches, an artificial neural network is design and implemented to capture effects of different parameters on the inplane vibration of sandwich arches. At the end, effects of several parameters including nonlocal and gradient parameters, geometrical aspect ratios and substrate constants of the structure on the natural frequency and amplitude is derived. It is observed that increasing nonlocal and gradient parameters have contradictory effects of the amplitude and frequency of vibration of the laminate beam.

• Smart Structures and Systems
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• 제25권5호
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• pp.619-630
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• 2020

This paper studies nonlinear free vibration characteristics of nonlocal magneto-electro-elastic (MEE) nanobeams resting on nonlinear elastic substrate having geometrical imperfection by considering piezoelectric reinforcement scheme. The piezoelectric reinforcement can cause an enhanced vibration behavior of smart nanobeams under magnetic field. All of previously reported studies on MEE nanobeams ignore the influences of geometric imperfections which are very substantial due to the reason that a nanobeam cannot be always perfect. Nonlinear governing equations of a smart nanobeam are derived based on classical beam theory and an analytical trend is provided to obtained nonlinear vibration frequency. This research shows that changing the volume fraction of piezoelectric constituent in the material has a great influence on vibration behavior of smart nanobeam under electric and magnetic fields. Also, it can be seen that nonlinear vibration behaviors of smart nanobeam are dependent on the magnitude of exerted electric voltage, magnetic potential, hardening elastic foundation and geometrical imperfection.

• 한국전기전자재료학회논문지
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• 제18권11호
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• pp.1014-1018
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• 2005

The purpose of this study is to obtain strong bond strength at the interface between piezoelectric substrates and semiconductor thin films to be applied for the manufacture of high-performance acoustic wave semiconductor coupled device. For this purpose, we have compared and examined the effects of different surface treatment methods on hydrophile properties at the surface of the piezoelectric substrates. Moreover, we have observed the effect of microwave and laser on the elimination of water molecules at the interface. As for the piezoelectric substrates, dry method for surface treatment was found to be superior in the control of hydrophilicity of the surface compared to wet method. On the other hand, both microwave and laser were found to be effective in the elimination of water molecules in the interface.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 추계학술대회 논문집 전기물성,응용부문
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• pp.61-62
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• 2006

In this study, in order to develop the low temperature sintering ceramics for multilayer piezoelectric actuator, PMN-PNN-PZT ceramics using ${Fe_2}{O_3}$ and $WO_3$ as sintering aids were manufactured with the amount of $WO_3$ addition, and the specimens were sintered at 900, 930, $960^{\circ}C$, respectively. Thereafter, their dielectric and piezoelectric properties were investigated. The sintering aids were proved to lower the sintering temperature of piezoelectric ceramics due to the effects of ${Fe_2}{O_3}$ and $WO_3$ liquid phase. At 0.3wt% $WO_3$ added specimen sintered at $930^{\circ}C$, kp, Qm, dielectric constant and $d_{33}$ showed the optimum values of 0.60, 1402, 1440 and 360[pC/N], respectively, for multilayer piezoelectric actuator application.

• Structural Engineering and Mechanics
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• 제23권2호
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• pp.163-175
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• 2006

In this paper, the dynamic response of a piezoelectric layer with a penny-shaped crack is investigated. The piezoelectric layer is subjected to an axisymmetrical action of both mechanical and electrical impacts. Two kinds of crack surface conditions, i.e., electrically impermeable and electrically permeable, are adopted. Based upon integral transform technique, the crack boundary value problem is reduced to a system of Fredholm integral equations in the Laplace transform domain. By making use of numerical Laplace inversion the time-dependent dynamic stress and electric displacement intensity factors are obtained, and the dynamic energy release rate is further derived. Numerical results are plotted to show the effects of both the piezoelectric layer thickness and the electrical impact loadings on the dynamic fracture behaviors of the crack tips.

• Smart Structures and Systems
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• 제12권3_4호
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• pp.381-397
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• 2013

In this paper, wireless health monitoring of stay cables using piezoelectric strain sensors and a smart skin technique is presented. For the cables, tension forces are estimated to examine their health status from vibration features with consideration of temperature effects. The following approaches are implemented to achieve the objective. Firstly, the tension force estimation utilizing the piezoelectric sensor-embedded smart skin is presented. A temperature correlation model to recalculate the tension force at a temperature of interest is designed by correlating the change in cable's dynamic features and temperature variation. Secondly, the wireless health monitoring system for stay cables is described. A piezoelectric strain sensor node and a tension force monitoring software which is embedded in the sensor are designed. Finally, the feasibility of the proposed monitoring technique is evaluated on stay cables of the Hwamyung Grand Bridge in Busan, Korea.

• 한국전기전자재료학회논문지
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• 제29권4호
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• pp.205-209
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• 2016

In this paper, piezoelectric ceramics with the composition of $(Na_{0.525}K_{0.4425}Li_{0.0375})(Nb_{0.8975}Sb_{0.065}Ta_{0.0375})O_3+0.3wt%\;CoO+x\;CuO$ ($0.005{\leq}x{\leq}0.025$) (abbreviated to NKL-NST) were fabricated for ultrasonic sensor application. The effects of CuO addition and sintering on the microstructure and the piezoelectric properties of the NKL-NST ceramics were systematically studied. Excellent piezoelectric properties such as electromchanical coupling $factor(k_p)=0.415$, piezoelectric constant $(d_{33})=166pC/N$ and piezoelectric figure of merit $d_{{33}*}g_{33}=5.47pm^2/N$ were obtained from the 2.5 mol% CuO doped NKL-NST+0.3 wt%CoO ceramics sintered at $1,000^{\circ}C$ for 3 h.