• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.1
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• pp.7-13
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• 2008

In this paper, the pumping performance of a piezoelectric valveless micropump is simulated with a commercial finite element analysis software, COMSOL Multiphysics. The micropump developed in the previous work is composed of a 4-layer lightweight piezo-composite actuator (LIPCA), a polydimethylsiloxane (PDMS) pump chamber, and two diffusers. The piezoelectric domain, structural domain and fluid domain are coupled in the simulation. Water flow rates are numerically predicted for geometric parameters of the micropump. Based on this study, the micropump is optimally designed to obtain its highest pumping performance.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.2 s.245
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• pp.120-127
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• 2006

The fatigue behavior of LIPCA was so sensitive to the manufacturing condition, the environmental factors and the change of the test apparatus. Therefore, we could be considering not only the relationship between the stroke range $({\Delta}h)$ and actuating frequency but also the relationship between the stroke range $({\Delta}h)$ and the total effective moment $(M^E)$. Thus, this study proposed the calculation method of the applying $M^E$ when the $({\Delta}h)$ of LIPCA was increased from 1.mm to 20mm. To estimate the relationship between the total effective moment $(M^E)$ and the Bernoulli-Euler bending moment (M) was reviewed. And the residual stress distribution of LIPCA and THUNDER using the CLT was evaluated. In conclusions, converting the $({\Delta}h)$ of LIPCA to the radius of curvature (p) and calculating the $(M^E)$, it was found that the p by the $M^E$ changed similarly as the $({\Delta}h)$. It was found that the $M^E$ was 2.2 times as the M. While CFRP and PZT of LIPCA, which had the superior compressive characteristic, had the compressive residual stress, GFRP was subject to the tensile residual stress. Since this reversed configuration between the compressive residuals stress and the tensile one was made, the requirement of the stroke range $({\Delta}h)$ increase was satisfied.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.429-434
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• 2007

This paper presents an experimental and parametric study of a biomimetic fish robot actuated by the Lightweight Piezo-composite Actuator(LIPCA). The biomimetic aspects in this work are the oscillating tail beat motion and shape of caudal fin. Caudal fins that resemble fins of BCF(Body and Caudal fin) mode fish were made in order to perform parametric study concerning the effect of caudal fin characteristics on thrust production at an operating frequency range. The observed caudal fin characteristics are the shape, area, and aspect ratio. It was found that a high aspect ratio caudal fin contributes to high swimming speed. The fish robot was propelled by artificial caudal fins shaped after thunniform-fish and mackerel caudal fins, which have relatively high aspect ratio, produced swimming speed as high as 2.364 cm/s and 2.519 cm/s, respectively, for 300 Vpp input voltage excited at 0.9 Hz. Thrust performance of the biomimetic fish robot was examined by Strouhal number, Froude number, Reynolds number, and Net forward force.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.3
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• pp.60-66
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• 2006

The purpose of this paper is to evaluate potential application of Lightweight Piezo-composite Actuator (LIPCA) to suppress vibrations of structures. The LIPCA, consisting of a piezoelectric layer, a carbon/epoxy layer and glass/epoxy layers, has advantages in terms of high performance, durability and reliability, compared to the bare piezoelectric ceramic (PZT) actuator. We performed two kinds of experiments on static actuation and active vibration suppression to investigate the actuation performances of the LIPCA and the bare PZT. We attached the actuator on one side and a strain gage on the other side of an aluminum beam. In the static actuation test, we evaluated the performance by comparing equivalent actuation moments of the LIPCA and the bare PZT due to the applied voltage. In the active vibration control test, control signals were generated to suppress the vibration of the beam by the PID control algorithm based on the measured strain signals. The performances were estimated based on settling times of the strain responses. It can be concluded that the LIPCA has better actuation performances than the bare PZT in active control of free vibration as well as static actuation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.8
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• pp.744-750
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• 2009

In this study, the pumping performance of a piezoelectric valveless micropump is simulated. The micropump, which was developed in the previous work, is composed of a four-layer lightweight piezocomposite actuator, a polydimethylsiloxane (PDMS) pump chamber, and two diffusers. The piezoelectric domain, the fluid domain and the structural domain are coupled in the three-dimensional simulation. We used ANSYS for the piezoelectric and structural domains and ANSYS CFX for the fluid domain. The effects of driven frequency on the flow rate have been investigated by simulating the flow characteristics for 10 Hz and 40 Hz driven frequencies. The flow rates with respect to driven frequencies up to 300 Hz have been calculated.

• Smart Structures and Systems
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• v.13 no.4
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• pp.587-614
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• 2014

In recent years the interest in online monitoring of lightweight structures with ultrasonic guided waves is steadily growing. Especially the aircraft industry is a driving force in the development of structural health monitoring (SHM) systems. In order to optimally design SHM systems powerful and efficient numerical simulation tools to predict the behaviour of ultrasonic elastic waves in thin-walled structures are required. It has been shown that in real industrial applications, such as airplane wings or fuselages, conventional linear and quadratic pure displacement finite elements commonly used to model ultrasonic elastic waves quickly reach their limits. The required mesh density, to obtain good quality solutions, results in enormous computational costs when solving the wave propagation problem in the time domain. To resolve this problem different possibilities are available. Analytical methods and higher order finite element method approaches (HO-FEM), like p-FEM, spectral elements, spectral analysis and isogeometric analysis, are among them. Although analytical approaches offer fast and accurate results, they are limited to rather simple geometries. On the other hand, the application of higher order finite element schemes is a computationally demanding task. The drawbacks of both methods can be circumvented if regions of complex geometry are modelled using a HO-FEM approach while the response of the remaining structure is computed utilizing an analytical approach. The objective of the paper is to present an efficient method to couple different HO-FEM schemes with an analytical description of an undisturbed region. Using this hybrid formulation the numerical effort can be drastically reduced. The functionality of the proposed scheme is demonstrated by studying the propagation of ultrasonic guided waves in plates, excited by a piezoelectric patch actuator. The actuator is modelled utilizing higher order coupled field finite elements, whereas the homogenous, isotropic plate is described analytically. The results of this "semi-analytical" approach highlight the opportunities to reduce the numerical effort if closed-form solutions are partially available.