• Structural Engineering and Mechanics
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• v.53 no.6
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• pp.1167-1182
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• 2015

In this study, the stresses and electric potential redistributions of a cylinder made from functionally graded piezoelectric material (FGPM) are investigated. All the mechanical, thermal and piezoelectric properties are modeled as power-law distribution of volume fraction. Using the coupled electro-thermo-mechanical relations, strain-displacement relations, Maxwell and equilibrium equations are obtained including the time dependent creep strains. Creep strains are time, temperature and stress dependent, the closed form solution cannot be found for this constitutive differential equation. A semi-analytical method in conjunction with the Mendelson method of successive approximation is therefore proposed for this analysis. Similar to the radial stress histories, electric potentials increase with time, because the latter is induced by the former during creep deformation of the cylinder, justifying industrial application of such a material as efficient actuators and sensors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.317-320
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• 1999

In this study, the piezoelectric ceramics PZT powder was synthesized by Wet-Dry combination method. And the flexible 1-3-0 type composites were fabricated with piezoceramic PZT and Eccogel polymer matrix embedded 3rd phase. Dielectric constant of 1-3-0 type composites was lower than that of single phase PZT ceramics. Thickness mode coupling factor k/sub t/ which was comparable with single phase PZT ceramics and mechanical quality factor Qm were about 0.65 and 6, respectively. These composites are considered as a good candidates for broad-band type transducer applications. The acoustic impedance of 1-3-0 type composites was lower than that of single phase PZT ceramics. Therefore, these composites would be better used for hydrophone applications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.625-629
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• 1999

In this study, in order to develop high sensitivity and low noise acoustic emission sensor, we manufactured the Pb(Zr, Ti)O$_3$ ceramics with the addition of WO$_3$ wt% to search for its required characteristics. Dielectric constant was increased as a function of the increase of WO$_3$ wt%. The Pb(Zr, Ti)O$_3$ (EC-65) ceramics added with 0.1lwt% WO$_3$ showed excellent dielectric constant and piezoelectric constants of 1931 and 199.55$\times$10$^{-12}$ (C/N), respectively. Accordingly It was shown as the composition ceramics suitable for AE sensor.

• Smart Structures and Systems
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• v.8 no.2
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• pp.191-204
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• 2011

A technique for damage localization and assessment based on measurements of both eigenvectors curvatures and eigenfrequencies is proposed. The procedure is based on two successive steps: a model independent localization, based on changes of modal curvatures, and the solution of a one-dimensional minimization problem to evaluate damage intensity. The observability properties of damage parameters is discussed and, accordingly, a suitable change of coordinates is introduced. The proposed technique is illustrated with reference to a cantilever Euler beam endowed with a set of piezoelectric transducers. To assess the robustness of the algorithm, a parametric study of the identification errors with respect to the number of transducers and to the number of considered modal quantities is carried out with both clean and noise-corrupted data.

• Steel and Composite Structures
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• v.27 no.4
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• pp.465-477
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• 2018

In this research, vibration and smart control analysis of a concrete foundation reinforced by $SiO_2$ nanoparticles and covered by piezoelectric layer on soil medium is investigated. The soil medium is simulated with spring constants and the Mori-Tanaka low is used for obtaining the material properties of nano-composite structure and considering agglomeration effects. With considering first order shear deformation theory, the total potential energy of system is calculated and by means of Hamilton's principle in three displacement directions and electric potential, the six coupled equilibrium equations are obtained. Also, based an analytical method, the frequency of system is calculated. The effects of applied voltage, volume percent and agglomeration of $SiO_2$ nanoparticles, soil medium and geometrical parameters of structure are shown on the frequency of system. Results show that with applying negative voltage, the frequency of structure is increased.

• Smart Structures and Systems
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• v.25 no.6
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• pp.643-655
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• 2020

Active control of nonlinear vibration of stiffened functionally graded (SFG) cylindrical shell is studied in this paper. The system is subjected to axial and transverse periodic loads in the presence of thermal uncertainty. The material composition is considered to be continuously graded in the thickness direction, also these properties depend on temperature. The relations of strain-displacement are derived based on the classical shell theory and the von Kármán equations. For modeling the stiffeners on the cylindrical shell surface, the smeared stiffener technique is used. The Galerkin method is used to discretize the partial differential equations of motion. Some comparisons are made to validate the SFG model. For suppression of the nonlinear vibration, the linear and nonlinear control strategies are applied. For control objectives, the piezoelectric actuator is attached to the external surface of the shell and the thin ring piezoelectric sensor is attached to the middle internal surface of shell. The effect of PID, feedback linearization and sliding mode control on the suppression of vibration for SFG cylindrical shell is presented.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11A
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• pp.904-908
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• 2009

The PZT(lead, zirconium, titanium) based ceramics which, are reported to be ferroelectric materials have their important applications in the areas of surface acoustic waves (SAW), filters, infrared detectors, actuators, ferroelectric random acess memory, speakers, electronic switches etc. Moreover, these PZT materials possess the large electromechanical coupling factor, large spontaneous polarization, low dielectric loss and low internal stress etc. Hence, keeping in view the unique properties of PZT piezoelectric ceramics we also tried to synthesize indigenously the small sized PZT ceramic powder in the laboratory by using the modified sol-gel approach. In this paper, Propyl alcohol based sol-gel method was used for preparation of PZT piezoelectric ceramic. The powder obtained by this sol-gel process was calcined and sintering to reach a pyrochlore-free crystal phase. The characterization of synthesized material was carried out by the XRD analysis and the surface morphology was determined by high resolution scanning electron microscopy.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.375-378
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• 2000

This paper investigated that resonant frequencies of microstrip patch antenna were tunable when piezoelectric materials were used as the antenna substrates. The resonant frequencies of the microstrip antenna using the piezoelectric substrate, like PZT, LiNbO$_3$ were able to be controlled by applied DC voltage. The frequency variation of the air gap antenna was 29MHz when the voltage variation was 14[kV/cm], and the frequency variation of microstrip patch antenna made of LiNbO$_3$substrate was 29MHz when voltage variation was 6[kV/cm].

• Electrical & Electronic Materials
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• v.3 no.4
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• pp.271-278
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• 1990

본 논문에서는 내부전극 Pt를 갖는 적층형 압전액튜에이터의 제조와 적층수에 따른 압전액튜에이터 압전특성에 대해 조사 연구하였다. 먼저, Dr.blade방법을 사용하여 두께 ~220.mu.m의 PZT green sheet를 제작하였다. green sheet의 밀도는 결합제 양과 외부압력에 대해 크게 의존하였으며 소결체의 밀도는 green sheet의 밀도가 커질수록 더 높게 나타났다. 다음에는 적층수에 따른 압전정수의 변화에 대한 것으로써 압전정수(d$_{33}$)는 PZT세라믹스의 적층수가 증가할수록 매우 크게 증가되었으며 압전정수를 도입하여 계산된 변형량(.DELTA.l/l)은 10층 시편에 대해 2*$10^{6}$V/m의 전계에서 3*$10^{-3}$값을 얻었다. 이와같은 결과로써 적층형 압전액튜에이터는 저전압에서도 큰 변위를 나타내며 따라서 제어장치의 미세작동에 충분히 이용 될 수가 있다.다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.05a
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• pp.73-76
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• 1992

In this study, piezoelectric ceramics of composition 0.08Pb(Mn$\sub$1/3/Sb$\sub$2/3/)O$_3$ were manufactured by the Hot-press method and structural, piezoelectrical properties and temperature stability were investigated with addition of 0, 02, 0.4, 0.6, 0.8, 1.0 [wt%] Cr$_2$O$_3$. Also the SAW delayline was fabricated and the propagation characteristics of SAW were considered with SAW theories.