• Advances in Computational Design
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• 제5권1호
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• pp.55-89
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• 2020

For the first time, an accurate analytical solution, based on coupled three-dimensional (3D) piezoelasticity equations, is presented for free vibration analysis of the angle-ply elastic and piezoelectric flat laminated panels under arbitrary boundary conditions. The present analytical solution is applicable to composite, sandwich and hybrid panels having arbitrary angle-ply lay-up, material properties, and boundary conditions. The modified Hamiltons principle approach has been applied to derive the weak form of governing equations where stresses, displacements, electric potential, and electric displacement field variables are considered as primary variables. Thereafter, multi-term multi-field extended Kantorovich approach (MMEKM) is employed to transform the governing equation into two sets of algebraic-ordinary differential equations (ODEs), one along in-plane (x) and other along the thickness (z) direction, respectively. These ODEs are solved in closed-form manner, which ensures the same order of accuracy for all the variables (stresses, displacements, and electric variables) by satisfying the boundary and continuity equations in exact manners. A robust algorithm is developed for extracting the natural frequencies and mode shapes. The numerical results are reported for various configurations such as elastic panels, sandwich panels and piezoelectric panels under different sets of boundary conditions. The effect of ply-angle and thickness to span ratio (s) on the dynamic behavior of the panels are also investigated. The presented 3D analytical solution will be helpful in the assessment of various 1D theories and numerical methods.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 추계학술발표대회 논문집
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• pp.286-289
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• 2004

This paper presents the fatigue characteristics of LIPCA (LIghtweight Piezo-Composite Actuator) device system. The LIPCA device system is composed of a piezoelectric ceramic layer and fiber reinforced lightweight composite layers. Typically a PZT ceramic layer is sandwiched by a top fiber layer with low CTE (coefficient of thermal expansion) and base layers with high CTE. The advantages of the LIPCA design are weight reduction by using the lightweight fiber reinforced plastic layers without compromising the generation of high force and large displacement and design flexibility by selecting the fiber direction and the size of prepreg layers. To predict the degradation of actuation performance of LIPCA due to fatigue, the cyclic electric loading tests using PZT specimens were performed and the strain for a given excitation voltage was measured during the test. The results from the PZT fatigue test were implemented into CLPT (Classical Laminated Plate Theory) model to predict the degradation of LIPCA's actuation displacement. The fatigue characteristic of PZT was measured using a test system composed of a supporting jig, a high voltage power supplier, data acquisition board, PC, and evaluated.

• Steel and Composite Structures
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• 제48권6호
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• pp.709-725
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• 2023

This paper uses a new type of deformation theory to establish the free vibration and static buckling equations of nanoplates resting on two-parameter elastic foundations, in which the flexoelectric effect is taken into account. The proposed approach used in this work is not only simpler than other higher-order shear deformation theories but also does not need any shear correction coefficients to describe exactly the mechanical responses of structures. The reliability of the theory is verified by comparing the numerical results of this work with those of analytical solutions. The results show that the flexoelectric effect significantly changes the natural frequency and the critical buckling load of the nanoplate compared with the case of neglecting this effect, especially when the plate thickness changes and with some different boundary conditions. These are new results that have not been mentioned in any publications but are meaningful in engineering practice.

• 대한기계학회논문집A
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• 제38권12호
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• pp.1335-1343
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• 2014

압전 페인트는 얇은 막의 형태로 선박이나 항공기 등에 도포되어 광범위한 면적에 발생되는 진동이나 충격을 검출하는 데 유용하게 사용될 수 있다. 본 논문은 압전 페인트가 코팅된 구조물에 충격이 가해졌을 경우 충격이 가해진 위치를 검출할 수 있는지 평가해 보고, 다양한 경계 조건에 대해 충격 위치 검출에 차이는 없는지 살펴보았다. 실험에 사용된 압전 페인트 센서는 네 영역으로 알루미늄 시편 위에 코팅되었고 분극 과정을 거친 후 한 영역에 충격이 가해졌을 경우 전압의 변화를 실시간 모니터링하였다. 실험 결과, 충격이 가해진 부분 외 나머지 영역에서는 충격신호의 크기가 매우 작아 충격 신호가 거의 검출되지 않았으며, 경계 조건과 무관하게 모든 조건에서 충격이 가해진 부분에서만 큰 충격 신호가 검출되었다.

• Steel and Composite Structures
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• 제33권6호
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• pp.891-906
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• 2019

This study considers the instability behavior of sandwich plates considering magnetorheological (MR) fluid core and piezoelectric reinforced facesheets. As facesheets at the top and bottom of structure have piezoelectric properties they are subjected to 3D electric field therefore they can be used as actuator and sensor, respectively and in order to control the vibration responses and loss factor of the structure a proportional-derivative (PD) controller is applied. Furthermore, Halpin-Tsai model is used to determine the material properties of facesheets which are reinforced by graphene platelets (GPLs). Moreover, because the core has magnetic property, it is exposed to magnetic field. In addition, Kelvin-Voigt theory is applied to calculate the structural damping of the piezoelectric layers. In order to consider environmental forces applied to structure, the visco-Pasternak model is assumed. In order to consider the mechanical behavior of structure, sinusoidal shear deformation theory (SSDT) is assumed and Hamilton's principle according to piezoelasticity theory is employed to calculate motion equations and these equations are solved based on differential cubature method (DCM) to obtain the vibration and modal loss factor of the structure subsequently. The effect of different factors such as GPLs distribution, dimensions of structure, electro-magnetic field, damping of structure, viscoelastic environment and boundary conditions of the structure on the vibration and loss factor of the system are considered. In order to indicate the accuracy of the obtained results, the results are validated with other published work. It is concluded from results that exposing magnetic field to the MR fluid core has positive effect on the behavior of the system.

• International Journal of Aeronautical and Space Sciences
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• 제6권1호
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• pp.17-26
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• 2005

An optical phase tracking technique for an extrinsic Fabry-Perot interferometer (EFPI) is proposed in order to overcome interferometric non-linearity. Basic idea is utilizing strain-rate information, which cannot be easily obtained from an EFPI sensor itself. The proposed phase tracking system consists of a patch-type EFPI sensor and a simple on-line phase tracking logic. The patch-type EFPI sensor comprises an EFPI and a piezoelectric patch. An EFPI sensor itself has non-linear behavior due to the interferometric characteristics, and a piezoelectric material has hysteresis. However, the composed patch-type EFPI sensor system overcomes the problems that can arise when they are used individually. The dynamic characteristics of the proposed phase tracking system were investigated, and then the patch-type EFPI sensor system was applied to the active suppression of flutter, dynamic aeroelastic instability, of a swept-back composite plate structure. The proposed system has effectively reduced the amplitude of the flutter mode, and increased flutter speed.

• 한국항공우주학회지
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• 제34권6호
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• pp.29-34
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• 2006

본 연구는 두께변화가 있는 복합소재 평판을 전파하는 램파의 전파특성을 실험을 통하여 살펴보았다. 상용 항공우주구조물에는 두께변화가 존재하는 부품이 많이 사용되고 있고 구조변화에 의해 두께가 변할 수도 있기 때문에 구조건전성 모니터링을 위하여 램파를 사용하고자 한다면, 이러한 구조물에 대한 램파의 특성을 면밀히 분석해 볼 필요가 있다. 본 연구는 얇은 두께의 PZT를 구조물 표면에 부착하여 실험을 수행하였다. 두께변화가 있는 전파경로를 선택하여 측정된 신호의 전파속도 및 주파수 분석 결과를 이상적 전파조건과 비교를 통하여 두께변화가 존재하는 영역에서 전파특성의 변화가 이루어지는 과정 중에 전이영역이 발생함을 제시하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.695-700
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• 1997

A direct boundary element method(DBEM) is developed for thin bodies whose surfaces are rigid or compliant. The Helmholtz integral equation and its normal derivative integral equation are adopted simultaneously to calculate the pressure on both sides of the thin body, instead of the jump values across it, to account for the different surface conditions of each side. Unlike the usual assumption, the normal velocity is assumed to be discontinuous across the thin body. In this approach, only the neutral surface of the thin body has to be discretized. The method is validated by comparison with analytic and/or numerical results for acoustic scattering and radiation from several surface conditions of the thin body; the surfaces are rigid when stationary or vibrating, and part of the interior surface is lined with a sound-absorbing material.

• Smart Structures and Systems
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• 제2권2호
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• pp.171-188
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• 2006

This paper deals with damage detection using active Lamb waves. The wavelet transform and empirical mode decomposition methods are discussed for measuring the Lamb wave's arrival time of the group velocity. An experimental system to diagnose the damage in the composite plate is developed. A method to optimize this system is also given for practical applications of active Lamb waves, which involve optimal arrangement of the piezoelectric elements to produce single mode Lamb waves. In the paper, the single mode Lamb wave means that there exists no overlapping among different Lamb wave modes and the original Lamb wave signal with the boundary reflection signals. Based on this optimized PZT arrangement method, five damage localizations on different plates are completed and the results using wavelet transform and empirical mode decomposition methods are compared.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 춘계학술대회 논문집
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• pp.492-497
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• 2011

일반적으로 헬리콥터는 양력, 추력 그리고 힘을 발생시키기 위해 로터 시스템을 사용하기 때문에 공력환경이 매우 복잡하다. 블레이드 와류 간섭과 같은 비정상 공력 환경이 발생한다. 이러한 비정상 공력 환경은 진동하중과 높은 공력소음을 유발한다. 진동하중과 공력소음은 로터 블레이드 회전수에 N 배의 해당하는 주파수 (N/rev)를 갖는다. 하지만 스와시 판과 피치링크로 이루어진 전통적인 로터 조종계통은 블레이드가 1 회 회전하는 동안 한번의 조종 변위를 발생시킬 수 있기 때문에 그러한 진동하중을 조절하기에는 한계가 있다. 이러한 문제를 해결하기 위해 많은 능동 제어 기법들이 개발되었다. 능동 제어기법은 임의의 주파수로 블레이드의 피치 각을 조종할 수 있다. 본 논문에서는 비정상 공력 하중을 변화시키기 위해 능동 제어기법 중 한 가지인 능동 뒷전 플랩 블레이드의 설계를 수행하였다. 능동 뒷전 플랩 블레이드는 에어포일의 캠버를 변화시키기 위해 작동기에 의해 구동되는 뒷전 플랩을 장착한다. 뒷전 플랩을 작동시키기 위해 블레이드 내부에 위치 압전 작동기를 사용하였다.