• Journal of the Korean Ceramic Society
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• v.26 no.6
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• pp.802-810
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• 1989

The temperature dependence of piezoelectric strain constant and the electric field induced strain are investigated as a function of PT in 0.5[xPT-(1-x)PZ]-0.5PNN ceramics. The piezoelectric strain constant d31 has the highest value(360$\times$10-12m/V) at PT=0.68. The temperature dependence of d31 is improved as Curie temperature of sample is increased, and the electric field dependence of induced strain is decreased with the coercive field increased. This ceramic system shows both piezoelectric effect and electrostrictive effect under the applied electric field. The piezoelectric of tetragonal phase is higher than that of rhombohedral phase, and the magnitude of electrostrictive constant is appeared in the order of morphotropic, rhombohedral and tetragonal phase. The piezoelectric strain constant with applied field must be considered theelectrostrictive effect due to 90$^{\circ}$domain wall displacements, and the displacement of bimorph type actuator agrees with the calulated value well.

• Korean Journal of Materials Research
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• v.25 no.10
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• pp.523-530
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• 2015

Electricity generation through fossil fuels has caused environmental pollution. To solve this problem, research on new renewable energy (solar, wind, geothermal heat, etc.) to replace fossil fuels is in progress. These devices are able to consistently generate power. However, they have many drawbacks, such as high installation costs and limitations in possible set-up environments. Thus, piezoelectric harvesting technology, which is able to overcome the limitations of existing energy technologies, is actively being studied. Piezoelectric harvesting technology uses the piezoelectric effect which occurs in crystals that generate voltage when stress is applied. Therefore, it has advantages such as a wider installation base and lower technological cost. In this study, a piezoelectric energy harvesting device based on constant wave motion was investigated. This device can regenerate electricity in a constant turbulent flow in the middle of the sea. The components of the device are circuitry, a steel bar, an bimorph piezoelectric element and buoyancy elements. In addition, a multiphysical analysis coupled with the structure and piezoelectric elements was conducted to estimate the performance of the device. With this piezoelectric energy harvesting device, the displacement and electric power were analyzed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1442-1445
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• 2003

In precision machinery industry, it's required with small size and low noise design to using in constant liquid delivery equipment. To accomplish it's purpose, we designed the check valve with rubber sheet of circle shapes as a possible assembly in pump body. The test equipment for piezoelectric pump was able to test pressure-flow property and output property of piezoelectric pump by variation(magnitude of voltage and frequency) of input power.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.225-228
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• 2001

A new three-dimensional thin shell element for the structure containing an integrated distributed piezoelectric sensor and actuator is proposed. A finite element formulation for the static response of the shell with piezoelectric sensor／actuator is derived. The assumed strain formulation and the bubble function improves the performance of the shell element. The verification through the calculation of the static response for the piezoelectic bimorph beam shows that the results agree with those from the theoretical analysis very well.

• Smart Structures and Systems
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• v.1 no.3
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• pp.309-324
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• 2005

This paper presents an efficient and accurate coupled beam model for piezoelectric bimorphs based on improved first-order shear deformation theory (FSDT). The model combines the equivalent single layer approach for the mechanical displacements and a layerwise modeling for the electric potential. General electric field function is proposed to reasonably approximate the through-the-thickness distribution of the applied and induced electric potentials. Layerwise defined shear correction factor (k) accounting for nonlinear shear strain distribution is introduced into both the shear stress resultant and the electric displacement integration. Analytical solutions for free vibrations and forced response under electromechanical loads are obtained for the simply supported piezoelectric bimorphs with series or parallel arrangement, and the numerical results for various length-to-thickness ratios are compared with the exact two-dimensional piezoelasticity solution. Excellent predictions with low error estimates of local and global responses as well as the modal frequencies are observed.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.9
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• pp.427-433
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• 2001

A linear ultrasonic motor was designed by a combination of the first longitudinal and fourth bending mode, and the motor consisted of a straight aluminum alloys bar bonded with a piezoelectric ceramic element as a driving element. That is,$L_1-B_4$ linear ultrasonic motor can be constructed by a multi-mode vibrator of longitudinal and bending modes. Linear ultrasonic motors are based on an elliptical motion on the surface elastic body, such as bar or plates. In general, the natural resonance frequency of the stator is used as a driving frequency of the motor which provides a large elliptical motion. The corresponding eigenmode of one resonance frequency can be excited twice at the same time with a Phase shift of 90 degrees in space and time. And the rotation can be reversed by changing the phase between the two signals from sin$\omega$t to cos$\omega$t. Moreover, the tangential force pushes the slider(rotor) and, therefore, determines the thrust and speed of the motor. The experimental results of fabrication motors, bimorph-tyPe motor showed more excellent than unimorph-type. The maximum speed of TBL-200, TBL-300, TBL-400, TBL -220, TBL-310 and TBL-420 motors were 0.12, 0.37, 0.39, 0.14, 0.55 and $0.60ms6{-1}$, respectively. And the efficiency were reported 1.15, 7.9, 6.6, 2.36, 10.1 and 16.5%, respectively. That time, output thrust of the motor was a strong(1~2N) and the weight of stator was a lightness(5~7g).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.4 s.247
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• pp.409-419
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• 2006

The actuating performance of plate-type unimorph piezoelectric composite actuators having various stacking sequences was evaluated by three dimensional finite element analysis on the basis of thermal analogy model. Thermal residual stress distribution at each layer in an asymmetrically laminated plate with PZT ceramic layer and thermally induced dome height were predicted using classical laminated plate theory. Thermal analogy model was applied to a bimorph cantilever beam and LIPCA-C2 actuator in order to confirm its validity. Finite element analysis considering thermal residual deformation showed that the bending behavior of piezoelectric composite actuator subjected to electric loads was significantly different according to the stacking sequence, thickness of constituent PZT ceramic and boundary conditions. In particular, the increase of thickness of PZT ceramic led to the increase of the bending stiffness of piezoelectric composite actuator but it did not always lead to the decrease of actuation distance according to the stacking sequences of piezoelectric composite actuator. Therefore, it is noted that the actuating performance of unimorph piezoelectric composite actuator is rather affected by bending stiffness than actuation distance.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1416-1418
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• 1994

Expressions for the displacement of a bimorph, one end fixed and the other free, has been introduced when sinusoidal inputs were applied to the ceramic plates on a thin metal plate. Maximum displacements at the free end and strains at the position of strain gage attached were measured when various wave forms, voltages, and frequencies were applied to the bimorph whose length is 6.6[cm], width 2.5[cm], and thickness 0.0365[cm]. Under the constant voltage ( $70[V_{peak}]$ ), the strains and the displacements at the free end were larger than the case of the sinusoidal input when the square wave was applied and were smaller when triangular wave. It was shown that the displacements at the free end and the strains of the gage position were increased as the applied voltage in the range of $30-90[V_{peak}]$ and effective length were increased. And it was also found that the resonant frequency of a bimorph was decreased as its effective length was increased, and that the displacements and the strains were maximum at the resonant frequency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.153-156
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• 2003

Many researchers have tried to develop the piezoelectric shell element and verified them with the benchmarking problem of the piezoelectric bimorph beam since there is no experimental result for the control of shell structure with piezoelectric sensor/actuator. In this paper, the experiments are designed and performed to verify the control Performance of piezoelectric sensor/actuator on the shell structure. PVDF is easy to be attached on the surface of a shell structure but makes weak control forces. On the contrary, PZT makes control forces large enough to control the structure, but it is not easy to make a PZT element with curvature. To use PVDF as an actuator, the structure should be designed as flexible as possible and the voltage amplifier could make high control voltage. PVDF actuator powered by a voltage amplifier that generates output voltage from -200 to +200 volts, shows little control performance to control the vibration of an arch type shell structure. The performance of sensor looks good and the negative velocity feedback control works perfectly. The actuator voltage seems to be too small to verify the control effect Quantitatively. An experiment with high voltage amplifier is scheduled to verify the control effect Quantitatively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.918-921
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• 2005

According to the mechanical-electrical coupling characteristics and the electrical Impedance property of resistor-inductor-capacitor(RLC) series resonant circuit, the mechanical impedance analysis of a bimorph piezoceramic patch shunted with a series RLC resonant circuit is conducted. The displacement transfer function of a cantilever beam bonded with a piezoelectric shunt damping module is deduced in the case of single mode vibration of the beam. By the use of vibration damping theory of tuned mass damper system, the parameter optimization of piezoelectric shunt damping system is performed. The optimal resonant state of the shunting circuit can be obtained when the resister and conductor are optimally adjusted. Test results show that the vibration control effect as well improved with optimized piezoelectric shunt system.