• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.171-174
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• 1998

Quartz crystal in contact with viscoelastic medium is described directly in terms of the electrical equivalent circuit of the system. Stearic acid is used as viscoelastic medium and deposited on the surface of quartz crystal using the Langmuir-Blodgett(LB) method. Impedance properties of quartz crystal coated with LB films which were investigated and the possibility of applying the technique to chemical sensing introduced.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.878-880
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• 1998

Quartz crystal in contact with viscoelastic medium is described directly in terms of the electrical equivalent circuit of the system. Stearic acid is used as viscoelastic medium and deposited on the surface of quartz crystal using the Langmuir-Blodgett(LB) method. Impedance properties of quartz crystal coated with LB films which were investigated and the possibility of applying the technique to chemical sensing introduced.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.189-195
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• 2008

The vibration isolator system(VIS) which has very low natural frequency could be designed by applying an axial compressive force to the beam-column flexure(BCF). In this paper a new shape of the BCF is suggested. It has stepwise axially varying properties by viscoelastic damping layer. So it has internal structural damping by damping layer during deformation. First the analytic solution is obtained for the BCF. And its critical load, buckling mode, stiffness and stress distributions are investigated. Also the dynamic properties of the VIS consist of the damping layered BCF are studied. Finally the optimal design procedure of damping layered BCF for the VIS is suggested. The improved performance of suggested VIS is verified by some experiments.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 1999.03a
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• pp.153-157
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• 1999

Voigt Model assumed for creep was used to obtain the viscoelastic properties of fabrics in thickness direction and the governing equation was derived. The weights were specially designed and calibrated for constant stress applied to fabrics and the 1 ${\mu}{\textrm}{m}$ resolution laser displacement sensor was attached in order to measure the variation of strain. Ten fabric samples were used. The few steps of strain showed according to the internal structure of fabrics. Also correlations the Hand Values from KESF with the spring and damping coefficients were considered.

• Smart Structures and Systems
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• v.20 no.5
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• pp.583-593
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• 2017

This research deals with the nonlocal temperature-dependent dynamic buckling analysis of embedded sandwich micro plates reinforced by functionally graded carbon nanotubes (FG-CNTs). The material properties of structure are assumed viscoelastic based on Kelvin-Voigt model. The effective material properties of structure are considered based on mixture rule. The elastic medium is simulated by orthotropic visco-Pasternak medium. The motion equations are derived applying Sinusoidal shear deformation theory (SSDT) in which the size effects are considered using Eringen's nonlocal theory. The differential quadrature (DQ) method in conjunction with the Bolotin's methods is applied for calculating resonance frequency and dynamic instability region (DIR) of structure. The effects of different parameters such as volume percent of CNTs, distribution type of CNTs, temperature, nonlocal parameter and structural damping on the dynamic instability of visco-system are shown. The results are compared with other published works in the literature. Results indicate that the CNTs have an important role in dynamic stability of structure and FGX distribution type is the better choice.

• Steel and Composite Structures
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• v.44 no.1
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• pp.91-104
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• 2022

The purpose of the present work is to study the parametric nonlinear vibration behavior of three layered symmetric laminated plate. In the analytical formulation; both normal and shear deformations are considered in the core layer by means of the refined higher-order zig-zag theory. Harmonic balance method in conjunction with Galerkin procedure is adopted for simply supported laminate plate, to obtain its natural and damping properties. For these aims, a set of complex amplitude equations governed by complex parameters are written accounting for the geometric nonlinearity and viscoelastic damping factor. The frequency response curves are presented and discussed by varying the material and geometric properties of the core layer.

• Composites Research
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• v.25 no.1
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• pp.9-13
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• 2012

In this research, biomechanical characteristics of the bone tissue are experimentally investigated. By using specimens of the bovine bone, the mechanical properties are obtained through tension and shear tests. In experiments, non-homogeneous and anisotropic properties with respect to longitudinal and transversal directions are observed. Moreover, the viscoelastic behavior in which modulus and strength properties are dependent on strain rates is analyzed. It is expected that a numerical damage model of the bone be efficiently established based on the results.

• Korea-Australia Rheology Journal
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• v.19 no.4
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• pp.183-190
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• 2007

Injection molding is one of the most common operations in polymer processing. Good quality products are usually obtained and major post-processing treatment is not required. However, residual stresses which exist in plastic parts affect the final shape and mechanical properties after ejection. Residual stresses are caused by polymer melt flow, pressure distribution, non-uniform temperature field, and density distribution. Residual stresses are predicted in this study by numerical methods using commercially available softwares, $Hypermesh^{TM},\;Moldflow^{TM}\;and\;ABAQUS^{TM}$. Cavity filling, packing, and cooling stages are simulated to predict residual stress field right after ejection by assuming an isotropic elastic solid. Thermo-viscoelastic stress analysis is carried out to predict deformation and residual stress distribution after annealing of the part. Residual stresses are measured by the hole drilling method because the automotive part selected in this study has a complex shape. Residual stress distribution predicted by the thermal stress analysis is compared with the measurement results obtained by the hole drilling method. The molded specimen has residual stress distribution in tension, compression, and tension from the surface to the center of the part. Viscoelastic deformation of the part is predicted during annealing and the deformed geometry is compared with that measured by a three dimensional scanner. The viscoelastic stress analysis with a thermal cycle will enable us to predict long term behavior of the injection molded polymeric parts.

• Journal of the Society of Naval Architects of Korea
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• v.36 no.1
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• pp.90-98
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• 1999

For the control of vibration and noise of metal structures having relatively low damping, viscoelastic materials are widely used and usually attached at metal structures with an additional constraining layer to secure them. The damping and elastic properties of structures having constrained viscoelastic material layers are dependent on not only temperature and frequency but also their thicknesses. Hence, optimal design of the thicknesses of viscoelastic and constraining layers for a certain base structure are very important to maximize their efficiency and to lighten their weight. In this study, the variation of loss factor of beams having a constrained viscoelastic layer according to the change of thickness has been carefully investigated. From these, optimal design method of the minimum thickness beam having a given loss factor is suggested and numerically verified for a real beam.

• Steel and Composite Structures
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• v.43 no.1
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• pp.79-90
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• 2022

In this study, the dynamic behavior of functionally graded layered deep beams with viscoelastic core is investigated including the porosity effect. The material properties of functionally graded layers are assumed to vary continuously through thickness direction according to the power-law function. To investigate porosity effect in functionally graded layers, three different distribution models are considered. The viscoelastically cored deep beam is exposed to harmonic sinusoidal load. The composite beam is modeled based on plane stress assumption. The dynamic equations of motion of the composite beam are derived based on the Hamilton principle. Within the framework of the finite element method (FEM), 2D twelve -node plane element is exploited to discretize the space domain. The discretized finite element model is solved using the Newmark average acceleration technique. The validity of the developed procedure is demonstrated by comparing the obtained results and good agreement is detected. Parametric studies are conducted to demonstrate the applicability of the developed methodology to study and analyze the dynamic response of viscoelastically cored porous functionally graded deep beams. Effects of viscoelastic parameter, porosity parameter, graduation index on the dynamic behavior of porous functionally graded deep beams with viscoelastic core are investigated and discussed. Material damping and porosity have a significant effect on the forced vibration response under harmonic excitation force. Increasing the material viscosity parameters results in decreasing the vibrational amplitudes and increasing the vibration time period due to increasing damping effect. Obtained results are supportive for the design and manufacturing of such type of composite beam structures.