• Composites Research
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• v.12 no.2
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• pp.1-9
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• 1999

The piezoelectric material connected to external electric networks possesses frequency dependent stiffness and loss factor which are also affected by the shunting circuit. The external electric networks are generally specialized for two shunting circuits: one is the case of a resistor alone and the other is the combination of a resistor and an inductor. For resistive shunting, the material properties exhibit frequency dependency similar to viscoelastic materials, but are much stiffer and more independent of temperature. Shunting with a resistor and inductor introduces an electrical resonance, which can change the characteristics of structural resonance optimally in a manner analogous to a PMD (proof mass damper). Passive damping enhancement of composite beam using piezoelectric material connected to external electrical networks is achieved and presented in this paper.

• Smart Structures and Systems
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• v.18 no.2
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• pp.335-354
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• 2016

This contribution presents an extended one-dimensional theory for piezoelectric beam-type structures with non-ideal electrodes. For these types of electrodes the equipotential area condition is not satisfied. The main motivation of our research is originated from passive vibration control: when an elastic structure is covered by several piezoelectric patches that are linked via resistances and inductances, vibrational energy is efficiently dissipated if the electric network is properly designed. Assuming infinitely small piezoelectric patches that are connected by an infinite number of electrical, in particular resistive and inductive elements, one obtains the Telegrapher's equation for the voltage across the piezoelectric transducer. Embedding this outcome into the framework of Bernoulli-Euler, the final equations are coupled to the wave equations for the longitudinal motion of a bar and to the partial differential equations for the lateral motion of the beam. We present results for the wave propagation of a longitudinal bar for several types of electrode properties. The frequency spectra are computed (phase angle, wave number, wave speed), which point out the effect of resistive and inductive electrodes on wave characteristics. Our results show that electrical damping due to the resistivity of the electrodes is different from internal (=strain velocity dependent) or external (=velocity dependent) mechanical damping. Finally, results are presented, when the structure is excited by a harmonic single force, yielding that resistive-inductive electrodes are suitable candidates for passive vibration control that might be of great interest for practical applications in the future.

• Structural Engineering and Mechanics
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• v.81 no.3
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• pp.317-333
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• 2022

Visco-Plastic Damper (VPD) as a passive energy dissipation device with dual behavior has been recently numerically studied. It consists of two bent steel plates and segments with a viscoelastic solid material in between, combining and improving characteristics of both displacement-dependent and velocity-dependent devices. In order to trust the performance of VPD, for the 1st time this paper experimentally investigates prototype damper behavior under a wide range of frequency and amplitude of dynamic loading. A high-axial damping rubber is innovatively proposed as the viscoelastic layer designed to withstand large axial strains and dissipate energy accordingly. Test results confirmed all assumptions about VPD. The behavior of VPD subjected to low levels of excitation is elastic while with increasing levels of excitation, a significant source of energy dissipation is provided through the yielding of the steel elements in addition to the viscoelastic energy dissipation. The results showed energy dissipation of 99.35 kN.m under a dynamic displacement with 14.095 mm amplitude and 0.333 Hz frequency. Lateral displacement at the middle of the device was created with an amplification factor obtained ranging from 2.108 to 3.242 in the rubber block. Therefore, the energy dissipation of viscoelastic material of VPD was calculated 18.6 times that of the ordinary viscoelastic damper.

• The Journal of the Acoustical Society of Korea
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• v.28 no.1
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• pp.25-31
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• 2009

This paper introduces a spectrally formulated element method (SEM) for the beams treated with passive constrained layer damping (PCLD). The viscoelastic core of the beams has a complex modulus that varies with frequency. The SEM is formulated in the frequency domain using dynamic shape functions based on the exact displacement solutions from progressive wave methods, which implicitly account for the frequency-dependent complex modulus of the viscoelastic core. The frequency response function and dynamic responses obtained by the SEM and the conventional finite element method (CFEM) are compared to evaluate the validity and accuracy of the present spectral PCLD beam element model. The spectral PCLD beam element model is found to provide very reliable results when compared with the conventional finite element model.

• 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 Aerospace System Engineering
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• v.18 no.1
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• pp.37-45
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• 2024

This paper presents a design approach for passive vibration control to reduce vertical vibrations transmitted to the control unit during hovering flight of a quadrotor drone. Ground vibration test simulation based on finite element model was performed for forced vibration analysis of the quadrotor drone. First, modal analysis was performed to evaluate dynamic characteristics. Forced vibration response analysis was then performed to obtain the steady-state response within the operating frequency range under the hovering flight condition. Furthermore, to obtain the vibration reduction effect, a viscous damping tape was applied at positions that could induce vibrations transmitted to the control unit under the same conditions. Such a passive vibration control approach was investigated. Relevant vibration reduction effect was assessed with respect to the application of damping materials and the attachment position.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.909-914
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• 2006

Vibration isolation tables are mostly required in precise measurement and manufacturing system. Among the vibration isolation tables, an air spring is the most favorable equipment because of low resonant frequency and high damping ratio. However, it is difficult to design the air spring with the required stiffness and damping ratio. Futhermore, whenever conventional active control methods are applied to the air spring, it may be difficult to obtain effective control performance due to high nonlinearity of air spring. In this paper, the optimal design of the air spring is performed using genetic algorithm to bring out low resonant frequency and high damping ratio. Also, active control of the vibration isolation table with 3-DOF model is proposed using the adaptive control method. Through experiments, optimal design is shown to be effective. And performance of the proposed control method is verified to be better than those of the passive control method and the conventional active control methods.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.6
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• pp.117-126
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• 1994

This paper deals with a robust semi-active control algorithm which is applicable to a semi-active suspension with a multi-state damper. Since the controllable damping rates are discrete in case of a multi-state semi-active damper, the desired damping rate can not be produced exactly even if force-velocity relations of a multi-state semi-active damper is completely known. In addition, damping characteristics of the semi-active dampers are different from damper to damper. A robust nonlinear control law based on sliding control is developed. The main objective of the proposed control strategies is to improve ride quality by tracking the desired active force with a multi-state damper of which the force-velocity relations are "not" completely known. The performance of th proposed semi-active control law is numerically compared to those of the control law based on a bilinear model and a passive suspension. The proposed control algorithm is robust to nonlinear characteristics and uncertainty of the force-Velocity relations of multi-state dampers.

• 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.

• Steel and Composite Structures
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• v.31 no.4
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• pp.387-396
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• 2019

This paper deals with the effect of ply orientation and control gain on tip transverse displacement of functionally graded beam layer for both active constrained layer damping (ACLD) and passive constrained layer damping (PCLD) system. The functionally graded beam is taken as host beam with a bonded viscoelastic layer in ACLD beam system. Piezoelectric fiber reinforced composite (PFRC) laminate is a constraining layer which acts as actuator through the velocity feedback control system. A finite element model has been developed to study actuation of the smart beam system. Fractional order derivative constitutive model is used for the viscoelastic constitutive equation. The control voltage required for ACLD treatment for various symmetric ply stacking sequences is highest in case of longitudinal orientation of fibers of PFRC laminate over other ply stacking sequences. Performance of symmetric and anti-symmetric ply laminates on damping characteristics has been investigated for smart beam system using time and frequency response plots. Symmetric and anti-symmetric ply laminates significantly reduce the amplitude of the vibration over the longitudinal orientation of fibers of PFRC laminate. The analysis reveals that the PFRC laminate can be used effectively for developing very light weight smart structures.