• Journal of Power Electronics
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• v.3 no.2
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• pp.139-144
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• 2003

In this paper, 11 and 13 layered step-down piezoelectric transformers were fabricated and their electrical characteristics have been analyzed for AC-adapter. When the voltage is applied to the driving piezoelectric vibrator polarized in the longitudinal direction, the output voltage is generated at the generating piezoelectric vibrator polarized in the thickness direction due to the piezoelectric effects. From the piezoelectric direct and converse effects, symbolic expressions between the electric inputs and outputs of the step-down piezoelectric transformer are derived with an equivalent circuit model. With those expressions, load and frequency characteristics are discussed through the simulations. Output voltage and current from a 11-layered and a 13-layered piezoelectric transformers were measured under the different load and frequency conditions. First we measured resonant frequency from impedance curve and got equivalent impedance value of the piezoelectric transformer from admittance plot. It was shown from experiments that output voltage increase s and resonant frequency changes according to the various resistor loads. Output current decreases inversely proportional to the change of loads. Moreover, the measured output voltage and current are well matched with the simulated results obtained from the proposed equivalent circuit model. Furthermore, a new step-down piezoelectric transformer has been suggested to Increase the output power based on a simulation result having a driving piezoelectric vibrator polarized thickness direction.

• Structural Engineering and Mechanics
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• v.24 no.4
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• pp.395-410
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• 2006

This paper reports the result of an investigation into wave propagation in orthotropic laminated piezoelectric cylindrical shells in hydrothermal environment. A dynamic model of laminated piezoelectric cylindrical shell is derived based on Cooper-Naghdi shell theory considering the effects of transverse shear and rotary inertia. The wave characteristics curves are obtained by solving an eigenvalue problem. The effects of layer numbers, thickness of piezoelectric layers, thermal loads and humid loads on the wave characteristics curves are discussed through numerical results. The solving method presented in the paper is validated by the solution of a classical elastic shell non-containing the effects of transverse shear and rotary inertia. The new features of the wave propagation in laminated piezoelectric cylindrical shells with various laminated material, layer numbers and thickness in hydrothermal environment and some meaningful and interesting results in this paper are helpful for the application and the design of the ultrasonic inspection techniques and structural health monitoring.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.389-392
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• 2001

In this paper, we have explained electrical characteristics of a step-down Rosen type piezoelectric transformer for AC-adapter. When the electric voltage is applied to the driving piezoelectric vibrator polarized in the longitudinal direction, then output voltage is generated at the generating piezoelectric vibrator polarized in the thickness direction due to the piezoelectric effects. Output voltage and current from a 11-layered and a 13-layered piezoelectric transformer were measured under the various conditions of loads and frequencies. We measured resonant frequency from impedance curve. It was shown from experiments that output voltage has increased and resonant frequency has changed according to various resistor loads. Output current has changed inversely proportional to resistances.

• Structural Engineering and Mechanics
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• v.65 no.4
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• pp.435-445
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• 2018

This paper is concerned with thermo-mechanical vibration behavior of flexoelectric/piezoelectric nanobeams under uniform and linear temperature distributions. Flexoelectric/piezoelectric nanobeams have higher natural frequencies compared to conventional piezoelectric ones, especially at lower thicknesses. Both nonlocal and surface effects are considered in the analysis of flexoelectric/piezoelectric nanobeams for the first time. Hamilton's principle is employed to derive the governing equations and the related boundary conditions which are solved applying a Galerkin-based solution. Comparison study is also performed to verify the present formulation with those of previous data. Numerical results are presented to investigate the influences of the flexoelectricity, nonlocal parameter, surface elasticity, temperature rise, beam thickness and various boundary conditions on the vibration frequencies of thermally affected flexoelectric/piezoelectric nanobeam.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.3B no.2
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• pp.67-73
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• 2003

In this paper, the impedance of a piezoelectric transducer is calculated using the three-dimensional finite element method. The validity of numerical routine is confirmed experimentally. Using this numerical routine, the effects of material coefficients on piezoelectric actuators characteristics are analyzed. The material constants, which make significant effects, are selected and the relations between material constants are studied. Using these processes, three variables of material constants for a piezoelectric transducer are selected and the design sensitivity method is adopted as an inversion scheme. The validity of the inversion scheme for a piezoelectric transducer is confirmed by applying the proposed method to the sample piezoelectric transducer.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.47-51
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• 2001

In this paper, we have explained electrical characteristics of a step-down Rosen type piezoelectric transformer for AC-adapter. When the electric voltage is applied to the driving piezoelectric vibrator polarized in the longitudinal direction, then output voltage is generated at the generating piezoelectric vibrator polarized in the thickness direction due to the piezoelectric effects. From the piezoelectric direct and converse effects, symbolic expressions between the electric inputs and outputs of the step-down piezoelectric transformer have derived with an equivalent circuit model. With the symbolic expressions, load and frequency characteristics have discussed through simulation. Output voltage and current from a 11-layered and a 13-layered piezoelectric transformers were measured under the various conditions of loads and frequencies. First we measured resonant frequency from impedance curve and got equivalent impedance value of the piezoelectric transformer from admittance plot. It was shown from experiments that output voltage has increased and resonant frequency has changed according to various resistor loads. Output current has decreased inversely proportional to changing of loads. Moreover, the measured values of output voltage and current are well agreed with the simulated values of the proposed equivalent circuit model.

• Structural Engineering and Mechanics
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• v.76 no.5
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• pp.619-629
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• 2020

In current study, surface/interface effects for pull-in voltage and viscous fluid velocity effects on dimensionless natural frequency (DNF) of fluid-conveying piezoelectric nanosensor (FCPENS) subjected to direct electrostatic voltage DC with nonlinear excitation, harmonic force and also viscoelastic foundation (visco-pasternak medium and structural damping) are investigated using Gurtin-Murdoch surface/interface (GMSIT) theory. For this analysis, Hamilton's principles, the assumed mode method combined with Lagrange-Euler's are used for the governing equations and boundary conditions. The effects of surface/interface parameters of FCPENS such as Lame's constants (λI,S, μI,S), residual stress (τ0I,S), piezoelectric constants (e31psk,e32psk) and mass density (ρI,S) are considered for analysis of dimensionless natural frequency respect to viscous fluid velocity u̅f and pull-in voltage V̅DC.

• Steel and Composite Structures
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• v.22 no.6
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• pp.1301-1336
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• 2016

In this paper, the free vibrations of a short cylindrical nanotube made of piezoelectric material are studied based on the consistent couple stress theory and using the shear deformable cylindrical theory. This new model has only one length scale parameter and can consider the size effects of nanostructures in nanoscale. To model size effects in nanoscale, and considering the nanotube material which is piezoelectric, the consistent couple stress theory is used. First, using Hamilton's principle, the equations of motion and boundary condition of the piezoelectric cylindrical nanoshell are developed. Afterwards, using Navier approach and extended Kantorovich method (EKM), the governing equations of the system with simple-simple (S-S) and clamped-clamped (C-C) supports are solved. Afterwards, the effects of size parameter, geometric parameters (nanoshell length and thickness), and mechanical and electric properties (piezoelectric effect) on nanoshell vibrations are investigated. Results demonstrate that the natural frequency on nanoshell in nanoscale is extremely dependent on nanoshell size. Increase in size parameter, thickness and flexoelectric effect of the material leads to increase in frequency of vibrations. Moreover, increased nanoshell length and diameter leads to decreased vibration frequency.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.232.2-232.2
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• 2015

Piezoelectric force microscopy (PFM) is a powerful method to characterize inversed piezoelectric effects directly using conductive atomic force microscopy (AFM) tips. Piezoelectric domains respond to an applied AC voltage with a characteristic strain via a contact between the tip and the surface of piezoelectric material. Electroactive piezoelectric polymers are widely investigated due to their advantages such as flexibility, light weight, and microactuation enabling various device features. Although piezoelectric polymers are promising materials for wide applications, they have the primary issue that the piezoelectric coefficient is much lower than that of piezoelectric ceramics. Researchers are studying widely to enhance the piezoelectric coefficient of the materials including nanoscale fabrication and copolymerization with some materials. In this report, nanoscale electroactive polymers are prepared by the electrospinning method that provides advantages of direct poling, scalability, and easy control. The main parameters of the electrospinning process such as distance, bias voltage, viscosity of the solution, and elasticity affects the piezoelectric coefficient and the nanoscale structures which are related to the phase of piezoelectric polymers. The characterization of such electroactive polymers are conducted using piezoelectric force microscopy (PFM). Their morphologies are characterized by field emission-scanning electron microscope (FE-SEM) and the crystallinity of the polymer is determined by X-ray diffractometer.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.943-946
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• 2007

In-plane piezoelectric charge constant of Electro-Active paper (EAPap) was investigated based on direct and converse piezoelectric effects. EAPap samples were made with cellulose film with very thin gold electrode coated on both sides of the film. To characterize direct piezoelectricity of EAPap, induced charge was measured when mechanical stress was applied to EAPap. In-plane piezoelectric charge constant was extracted from the relation between induced charge and applied in-plane normal stress. To investigate converse piezoelectricity, induced in-plane strain was measured when electric field was applied to EAPap. Piezoelectric charge constant was also extracted from the relation of induced in-plane strain and applied electric field. Piezoelectric charge constants obtained from direct and converse piezoelectricity are 31 pC/N and 178 x 10-12m/V for 45 degree sample, respectively. Measured piezoelectric charge constants of EAPap provide promising potential as a piezoelectric material.