• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.10
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• pp.1514-1519
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• 2001

This paper is concerned with design, manufacturing and performance test of LIPCA ( Lightweight Piezo- composite Curved Actuator) using a top carbon fiber composite layer with near -zero CTE(coefficient of thermal expansion), a middle PZT ceramic wafer and a bottom glass/epoxy layer with high CTE. The main point of this design is to replace the heavy metal layers of THUNDER by thigh tweight fiber reinforced plastic layers without losing capabilities to generate high force and large displacement. It is possible to save weight up to about 30% if we replace the metallic backing material by the light fiber composite layer. We can also have design flexibility by selecting the fiber direction and the size of prepreg layers. In addition to the lightweight advantage and design flexibility, the proposed device can be manufactured without adhesive layers when we use epoxy resin prepreg system. Glass/epoxy prepregs, a ceramic wafer with electrode surfaces, and a graphite/epoxy prepreg were simply stacked and cured at an elevated temperature (177 $^{circ}C$ after following an autoclave bagging process. It was found that the manufactured composite laminate device had a sufficient curvature after detached from a flat mold. The analysis method of the cure curvature of LIPCA using the classical lamination theory is presented. The predicted curvatures are fairly in agreement with the experimental ones. In order to investigate the merits of LIPCA, a performance test of both LIPCA and THUNDE$^{TM}$ were conducted under the same boundary conditions. From the experimental actuation tests, it was observed that the developed actuator could generate larger actuation displacement than THUNDERT$^{TM}$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.661-664
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• 1999

The piezoelectric properties and the doping effect of Nb$_2$O$_{5}$ for 0.95 PbZr$_{x}$ Ti$_{1-x}$ -O$_3$+0.05 Pb(Mnsub 1/3/Nb$_{2}$3/)O$_3$ compositions have been investigated. In the composition of 0.95PbZr$_{0.51}$Ti$_{0.49}$O$_3$+0.05Pb(Mn$_{1}$3/Nb/syb 2/3/)O$_3$ the values of k$_{p}$ and $\varepsilon$$_{33}$ $^{T}$ are maximized, but Q$_{m}$ was minimized (k$_{p}$ =0.57, Q$_{m}$ =1550). The grain size was suppressed and the uniformity of grain was improves with doping concentration of Nb$_2$O$_{5}$ far 0.95PbZr$_{0.51}$Ti$_{0.49}$O$_3$+0.05Pb(Mn$_{1}$3/Nb/syb 2/3/)O$_3$. sample. The values of k$_{p}$ first decreased slightly when a small amount of Nb$^{5+}$ is doped and then decreased when the Nb$^{5+}$ concentration is further increased. The Q$_{m}$ . OR the Other hand. increased monotonously with doping concentration of Nb$_2$O$_{5}$ .{5}$ . .

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.1
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• pp.72-79
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• 2022

Piezoelectric energy harvesting technologies, which can be used to convert the electricity from the mechanical energy, have been developed in order to assist or power the wearable electronics. To realize non-toxic and biocompatible electronics, the lead-free (Ba_0.85Ca_0.15)(Ti_0.90Zr_0.10)O₃ (BCTZ) nanoparticles (NPs) are being studied with a great attention as flexible energy harvesting device. Herein, piezoelectric hybrid nanocomposites were fabricated using BCTZ NPs-embedded poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] matrix to improve the performance of flexible energy harvester. Output performance of the fabricated energy device was investigated by the well-optimized measurement system during the periodically bending and releasing motions. The generated open-circuit voltage and the short-circuit current of the piezoelectric hybrid nanocomposite-based energy harvester reached up to ~15 V and ~1.1 ㎂, respectively; moreover, the instantaneous power of 3.5 ㎼ is determined from load voltage and current at the external load of 20 MΩ. This research is expected to cultivate a new approach to high-performance wearable self-powering electronics.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.206-206
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• 2008

압전소자를 이용한 초음파 모터는 전자기적 원리로 동작하는 기존의 모터에 비해 구조가 간단하고 소형, 경량화가 가능하며 저속에서 큰 토크가 가능하고 ${\mu}m$단위 까지 정밀제어가 가능하다는 장점 등으로 인해 그 응용분야가 점차 확대되고 있다. 초음파 모터의 원리는 수평과 수직방향에서 변위가 타원형 운동을 형성하는 것이다. 따라서 선택한 타원운동의 방식에 의해서 모터의 형상이 달라진다. 초음파 모터는 액츄에이터를 사용하여 만들기 때문에 액츄에이터의 특성은 모터의 타원변위나 토크에 영향을 미친다. 단판형 액츄에이터에 비하여 적층 액츄에이터는 입력 임피던스를 낮추어 낮은 구동전압에서 구동이 가능하며 큰 변위와 토크를 발생하기 때문에 진동자의 수명 향상과 구동전압을 낮추기에 적합하다. 적층 액츄에이터는 변위량이나 응력 등을 개선하기 위해서 전기기계 결합계수(kp) 및 압전 d상수가 큰 재료가 요구되며, 고전압에서 장시간 구동 시 마찰에 의한 열손실을 감소시키기 위해 높은 기계적 품질계수(Qm)를 가져야한다. 적층 시 내부전극으로 사용하는 Pd, Pt가 함유된 전극은 가격이 비싸 제조비용을 상승시킨다. 상대적으로 값싼 Ag전극을 사용하면 비용절감을 할 수 있지만 융점이 낮아서 저온소결이 불가피하다. 따라서, 특성이 우수한 적층 액츄에이터를 제조하기 위해서 저손실, 저온소결 할 수 있는 액츄에이터 재료가 필요한 실정이다. L1-B4 혈 선혈 초음파 모터는 L1모드와 B4모드의 공진 주파수가 일치하여야 큰 변위를 얻을 수 있는데 이전의 논문에서 Atila를 이용한 시뮬레이션 결과를 분석한 봐 있다. 적층 액츄에이터의 층수를 5,7,9,11,13,15층으로 하여 L1-B4모드에서의 공진주파수를 비교한 결과 13 층일 때 두 모드가 비슷한 공진주파수를 보였고, 티원변위궤적도 다른 층수에 비해 크게 나타났다. 본 연구에서는 시뮬레이션 결과 가장 좋은 특성을 보인 13층 액츄에이터로 선형 초음파 모터를 제작하였다. 또한, 액츄에이터는 압전 및 유전특성이 우수한 저온소결 PZW-PMN-PZT세라믹을 이용하여 제작하였고, 내부전극으로 Ag전극을 사용하였다. 제작된 13 층 선형초음파모터를 가지고 프리로드 및 전압에 따른 속도를 조사하였고, 시뮬레이션 결과와 비교해 보았다.

• Composites Research
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• v.13 no.5
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• pp.50-59
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• 2000

In this paper, two methods to suppress flutter of the composite panel are examined. First, in the active control method, a controller based on the linear optimal control theory is designed and control input voltage is applied on the actuators and a PZT is used as actuator. Second, a new technique, passive suppression scheme, is suggested for suppression of the nonlinear panel flutter. In the passive suppression scheme, a shunt circuit which consists of inductor-resistor is used to increase damping of the system and as a result the flutter can be attenuated. A passive damping technology, which is believed to be more robust suppression system in practical operation, requires very little or no electrical power and additional apparatuses such as sensor system and controller are not needed. To achieve the great actuating force/damping effect, the optimal shape and location of the actuators are determined by using genetic algorithms. The governing equations are derived by using extended Hamilton's principle. They are based on the nonlinear von Karman strain-displacement relationship for the panel structure and quasi-steady first-order piston theory for the supersonic airflow. The discretized finite element equations are obtained by using 4-node conforming plate element. A modal reduction is performed to the finite element equations in order to suppress the panel flutter effectively and nonlinear-coupled modal equations are obtained. Numerical suppression results, which are based on the reduced nonlinear modal equations, are presented in time domain by using Newmark nonlinear time integration method.

• Journal of the Korean Ceramic Society
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• v.38 no.10
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• pp.942-947
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• 2001

Thickness dependence of orientation on piezoelectric and electrical properties was investigated by PZT (52/48) films by diol based sol-gel method. The thickness of each layer by spinning at one time was $0.2{\mu}m$ and crack-free films could be successfully deposited on 4 inches Pt/Ti/$SiO_2$/Si substrates by 0.5 mol solutions in the range from $0.2{\mu}m$ to $3.8{\mu}m$. Excellent P-E hysteresis curves were achieved, which were attributed to the well-densified PZT films and columnar grain without pores or any defects between interlayers. The (111) preferred orientation of films were shown in the range of thickness below $1{\mu}m$. As the thickness increased, the (111) preferred orientation disappeared from $1{\mu}m$ to $3{\mu}m$ region, and the orientation of films became random above $3{\mu}m$. Dielectric constants and longitudinal piezoelectric coefficient, $d_{33}$, measured by pneumatic method were saturated around the value of about 1400 and 300 pC/N respectively above the thickness of $1{\mu}m$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.5
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• pp.418-425
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• 2019

A piezoelectric ceramic fiber composite (PCFC) was successfully fabricated using $0.69Pb(Zr_{0.47}Ti_{0.53})O_3-0.31[Pb(Zn_{0.4}Ni_{0.6})_{1/3}Nb_{2/3}]O_3$ (PZT-PZNN) for use in small-scale wind energy harvesters. The PCFC was formed using an epoxy matrix material and an array of Ag/Pd-coated PZT-PZNN piezo-ceramic fibers sandwiched by Cu interdigitated electrode patterned polyethylene terephthalate film. The energy harvesting performance was evaluated in a custom-made wind tunnel while varying the wind speed and resistive load with two types of flutter wind energy harvesters. One had a five-PCFC array vertically clamped with a supporting acrylic rod while the other used the same structure but with a five-PCFC cantilever array. Stainless steel (thickness: $50{\mu}m$) was attached onto one side of the PCFC to form the PZT-PZNN cantilever. The output power, in general, increased with an increase in the wind speed from 2 m/s to 10 m/s for both energy harvesters. The highest output power of $15.1{\mu}W$ at $14k{\Omega}$ was obtained at a wind speed of 10 m/s for the flutter wind energy harvester with the PZT-PZNN cantilever array. The results presented here reveal the strong potential for wind energy harvester applications to supply sustainable power to various IoT micro-devices.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.5
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• pp.471-479
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• 2022

Recently, piezoelectric devices, such as ultrasonic surgery, ultrasonic atomizer, and ultrasonic speaker, are analyzed and designed by finite element simulation methods. However, the discrepancy between the design and the experiment results of the device typically occurs due to the inaccuracy of the piezoelectric material properties. To improve the simulation accuracy, the material properties of the PZT ceramics were better refined using parameter estimation method. The material parameters are elastic stiffness c^E_ij and piezoelectric constant e_ij of PZT ceramics. The impedance curve characteristics for the LTE mode of PZT ceramics were calculated. The mismatch between the simulation and the experimental data were compared and minimized by a least square method. Finally, the simulated impedance data were compared with the experimental data for the various vibration modes of PZT ceramics and the optimized material properties of PZT ceramics were verified. To further verify the accuracy, this method was also applied to piezoelectric PMN-PT single crystals.

• Journal of the Korean Ceramic Society
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• v.19 no.4
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• pp.293-299
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• 1982

The effects of $MnO_2$ and $Cr_2O_3$ on the Piezoelectrictric properties of Pb(Mg1/2W1/2)0.3 Ti0.4 Zr0.3O3 Ceramics. Electromechanical properties in the system in connection with the sintering temperature and the effects of $MnO_2$ and $Cr_2O_3$ addition. The dielectric constant of the ceramics decreased with the additions of $MnO_2$ while the additions of $Cr_2O_3$ increased the value. The Planar coupling factor (Kp) of the ceramics with 0.2wt% $MnO_2$ and with 0.2wt% $Cr_2O_3$ gave the highest value of 0.52 and 0.513 as sintered at 106$0^{\circ}C$, 108$0^{\circ}C$, respectively. The value of mechanical Q-factor were in parallel with the fired density of the ceramics. The optical micrography of the sintered bodies showed that the additions of $MnO_2$ promoted the grain growth, while the additions of $Cr_2O_3$ retarded the grain growth.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.2
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• pp.101-108
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• 2007

This paper presents an efficient meshless method for analyzing cracked piezoelectric structures subjected to mechanical and electrical loading. The method employs an element free Galerkin (EFG) formulation and an enriched basic function as well as special shape functions that contain discontinuous derivatives. Based on the moving least squares (MLS) interpolation approach, The EFG method is one of the promising methods for dealing with problems involving progressive crack growth. Since the method is meshless and no element connectivity data are needed, the burdensome remeshing procedure required in the conventional finite element method (FEM) is avoided. The numerical results show that the proposed method yields an accurate near-tip stress field in an infinite piezoelectric plate containing an interior hole. Another example is to study a ceramic multilayer actuator. The proposed model was found to be accurate in the simulation of stress and electric field concentrations due to the abrupt end of an internal electrode.