• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.565-566
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• 2007

• Steel and Composite Structures
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• v.25 no.2
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• pp.141-155
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• 2017

This paper presents an investigation into the magneto-thermo-mechanical vibration and damping of a viscoelastic functionally graded-carbon nanotubes (FG-CNTs)-reinforced curved microbeam based on Timoshenko beam and strain gradient theories. The structure is surrounded by a viscoelastic medium which is simulated with spring, damper and shear elements. The effective temperature-dependent material properties of the CNTs-reinforced composite beam are obtained using the extended rule of mixture. The structure is assumed to be subjected to a longitudinal magnetic field. The governing equations of motion are derived using Hamilton's principle and solved by employing differential quadrature method (DQM). The effect of various parameter like volume percent and distribution type of CNTs, temperature change, magnetic field, boundary conditions, material length scale parameter, central angle, viscoelastic medium and structural damping on the vibration and damping behaviors of the nanocomposite curved microbeam is examined. The results show that with increasing volume percent of CNTs and considering magnetic field, material length scale parameter and viscoelastic medium, the frequency of the system increases and critically damped situation occurs at higher values of damper constant. In addition, the structure with FGX distribution type of CNTs has the highest stiffness. It is also observed that increasing temperature, structural damping and central angle of curved microbeam decreases the frequency of the system.

• Journal of Veterinary Clinics
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• v.15 no.2
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• pp.364-369
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• 1998

The purposes of the present study were to compare the effects of viscoelastic materials available in phacoemulsification in dogs and to evaluate $ARTZ^{\circledR}$ as their substitute. Six eyes from the healthy adult dogs were used in each group with different viscoelastic materials, $Healon$^{\circledR}, Viscoat^{\circledR}$ and $Occucoat^{\circledR} and ARTZ^{\circledR}$. The phacoemulsification was carried out with surgical micmscope(Leica M65l, Germany) and pbacoemulsiscation gystemGfidek 6000, Japan). $ARTZ^{\circledR}$ had lower pseudoplasocity than other viscoelastics. There was not significant difference in phacotime, rate of posterior capsule rupture, incidence of the intraocular inflammation among the viscoelastic materials. The corneal thickness in all groups was significantly increased in a day after operation and decreased gradually. However $ARTZ$^{\circledR}$ had more time to recover the preoperative thickness than the others. CoBiunctival congestion in the group with $ARTZ^{\circledR}$ was more severe but. there were no postoperative posterior capsule opacity and visual loss. The present study indirated that $ARTZ^{\circledR}$ could be used as viscoelastic material in dogs with respect to the vision after surgery.

• 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.

• Journal of Mechanical Science and Technology
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• v.20 no.8
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• pp.1139-1148
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• 2006

This paper addresses the analytical modeling and dynamic response of the advanced composite rotating blade modeled as thin-walled beams and incorporating viscoelastic material. The blade model incorporates non-classical features such as anisotropy, transverse shear, rotary inertia and includes the centrifugal and coriolis force fields. The dual technology including structural tailoring and passive damping technology is implemented in order to enhance the vibrational characteristics of the blade. Whereas structural tailoring methodology uses the directionality properties of advanced composite materials, the passive material technology exploits the damping capabilities of viscoelastic material (VEM) embedded into the host structure. The VEM layer damping treatment is modeled by using the Golla-Hughes-McTavish (GHM) method, which is employed to account for the frequency-dependent characteristics of the VEM. The case of VEM spread over the entire span of the structure is considered. The displayed numerical results provide a comprehensive picture of the synergistic implications of both techniques, namely, the tailoring and damping technology on the dynamic response of a rotating thin-walled b ε am exposed to external time-dependent excitations.

• Composites Research
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• v.16 no.5
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• pp.39-44
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• 2003

Embedding viscoelastic-damping materials into composites can greatly increase the damping properties of composite structures. Usually viscoelastic-damping materials behave isotropically so that their damping properties are the same in all directions. In these days, there is a desire to develop viscoelastic-damping materials that behave orthotropically so that damping properties vary with material orientation. These orthotropic damping materials can be made by embedding rows of thin wires within the viscoelastic materials. These wires add significant directional stiffness to the damping materials. where the stiffness variation with wire orientation follows classical lamination theory. In this paper, the loss factor of composite laminate was evaluated based on Ni and Adams' theory. To investigate the effect of directional damping material, the low-velociy impact response analysis was also performed. The present analysis results show that directional damping material has a great influence on vibration and damping characteristic of composite laminate.

• Structural Engineering and Mechanics
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• v.66 no.2
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• pp.249-262
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• 2018

In this paper, reaction of functionally graded (FG) thick nanoplates resting on a viscoelastic foundation to a moving nanoparticle/load is investigated. Nanoplate is assumed to be thick by using second order shear deformation theory and small-scale effects are taken into account in the framework of Eringen's nonlocal theory. Material properties are varied through the thickness using FG models by having power-law, sigmoid and exponential functions for material changes. FG nanoplate is assumed to be on a viscoelastic medium which is modeled using Kelvin-Voight viscoelastic model. Galerkin, state space and fourth-order Runge-Kutta methods are employed to solve the governing equations. A comprehensive parametric study is presetned to show the influence of different parameters on mechanical behavior of the system. It is shown that material variation in conjunction with nonlocal term have a significant effect on the dynamic deformation of nanoplate which could be used in comprehending and designing more efficient nanostructures. Moreover, it is shown that having a viscoelastic medium could play an important role in decreasing these dynamic deformations. With respect to the fresh studies on moving atoms, molecules, cells, nanocars, nanotrims and point loads on different nanosctructures using scanning tunneling microscopes (STM) and atomic force microscopes (AFM), this study could be a step forward in understanding, predicting and controlling such kind of behaviors by showing the influence of the moving path, velocity etc. on dynamic reaction of the plate.

• Journal of Aerospace System Engineering
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• v.11 no.6
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• pp.34-41
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• 2017

As an alternative of the existing honeycomb shock absorbing device, the new approach on shock absorbing design using the extrusion of hyper-viscoelastic material such as silicon rubber is studied in this paper. The strain energy and stress-strain characteristic of viscoelastic material at extrusion process through the metered orifice has a similarity with the honeycomb core for maximizing shock absorbing capability. And in order to evaluate the design feasibility of this device and to understand the shock absorbing mechanism of energy transformation, finite element analysis and quasi-static compression test of the multi-stage extrusion shock absorber are examined in this paper.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.70-73
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• 2009

The aim of this research is to obtain a numerical material model for an amorphous glassy polymer, polycarbonate (PC), which can be used in finite element analysis (FEA) of the micro thermal imprint process near the glass transition temperature. An understanding of the deformation behavior of the PC specimens was acquired by performing tensile stress relaxation tests. The viscoelastic material model based on generalized Maxwell model was introduced for the material near Tg to establish the FE model based on the commercial FEA code ABAQUS/Standard with a suitable set of parameters obtained for this material model from the test data. Further validation of the model and parameters was performed by comparing the analysis of FE model results to the experimental data.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.12
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• pp.950-955
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• 2002

The coupled finite/boundary element method is used in numerical analysis for acoustic radiation from the vibration of rectangular composite plate which is simply supported. This analysis is validated using the Wallace equation for an isotropic plate. Active control of sound fields has been tarried out using 3 pairs of piezoelectric sensor/actuator and a pair of viscoelastic material by Passive constrained layer damping treatment. The results show that the optimal placement of piezoelectric sensor/actuator and VE patch is required to control the sound fields from a vibrating composite plate.