• 한국정밀공학회지
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• 제34권3호
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• pp.167-172
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• 2017

This study proposes a method for identifying correlations between tension and drop height for sessile droplets in a roll-to-roll processing system. The effect of tension and drop height on the contact angle of a sessile droplet is presented. Design of experiment (DOE) methodology and statistical analysis are used to define a correlation between the process parameters. The contact angle is decreased while increasing tension and drop height. The influence of the tension is less significant on the contact angle compared with the effect of the drop height. However, tension should be considered as a major parameter because it is not easy to fix with roll eccentricity and compensating speed of the driven roll. The results of this study show that the effect of tension on the contact angle of a sessile droplet is more important than drop height because the drop height is fixed when the process systems are determined.

• 한국전산구조공학회논문집
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• 제24권1호
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• pp.33-41
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• 2011

본 연구에서는 비부착형 포스트텐션 시스템의 해석에 적용할 수 있는 모델링기법을 제시하였다. 모델링은 유한요소 해석 프로그램을 이용하였으며, tube-to-tube contact 요소를 도입하여 강연선의 물리적 형상을 직접적으로 모델링하는 방법과 실제의 강연선 외에 가상의 강연선을 콘크리트에 매입하고, 두 개의 강연선을 스프링으로 연결하여 간접적으로 모델링하는 방법을 동시에 제시하고 비교하였다. 콘크리트의 인장경화 현상을 무시하였을때 두 모델링기법에서는 거의 동일한 결과를 제공하지만 콘크리트의 인장경화를 고려한 경우에는 스프링을 이용한 간접적인 모델링기법을 통해서만 결과를 얻을 수 있었으며, 결과 또한 콘크리트의 경화현상을 고려하지 않은 경우와 다소 상이하였다. 비교를 통하여 비부착형 포스트텐션 시스템의 모델링기법으로 스프링을 이용한 모델링기법을 최종적으로 선정하고 기존의 실험적 연구에서 인용한 실험결과와 해석결과를 비교, 검증하였으며 또한 파라미터 스터디를 통해서 모델링의 적절성을 확인하였다.

• 한국소음진동공학회논문집
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• 제12권8호
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• pp.639-647
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• 2002

The nonlinear vibration of the thin perforated plate is analyzed in consideration of the V-shaped tension distribution and the effect of wire impact damping. The reduced order FEM model of the tension plate is obtained from dynamic condensation for the mass and stiffness matrices. Tension wire is modeled using the lumped parameter method to effectively describe its contact interactions with the plate. The nonlinear contact-impact model is composed of spring and damper elements, of which parameters are determined from the Hertzian contact theory and the restitution coefficient, respectively. From the evaluation of the computational accuracy and computation time for the deduced impact stiffness and damping coefficient, we determined proper values for the simulation works, accounting for the computational accuracy as well as the computational efficiency. Finally we discussed the results of nonlinear nitration analysis for variations of their design parameters.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.619-620
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• 2013

• Journal of Magnetics
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• 제21권2호
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• pp.261-265
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• 2016

Surface tension is a major factor in the thermodynamics as well as fluid properties of Magneto-Rheological Fluids (MRF). We measured the surface tension of an MRF using two different methods. A wettability characterization based on contact angles measurements for the fluid interacting with two different surfaces was conducted. A hydrocarbon based commercial MRF with more than 80% solid weight, placed on quartz and poly-tetra-fluoroethylene (PTFE) surfaces was used. We measured the fluids' surface tension value by means of contact angles measurements and by the falling drop method.

• Macromolecular Research
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• 제17권6호
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• pp.388-396
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• 2009

The surface properties (water sorption and repellency, adhesion) are closely related to the surface tension of polymer solids. The critical surface tension (${\gamma}_c$) and surface tension (${\gamma}_s$) of a polymer solid were estimated by the contact angle method by our quantitative imaging system. BPDA (3,3',4,4'-biphenyl tetracarboxylic dianhydride)-BAPP (1,3-Bis(4-aminophenoxy) propane) polyimide was successfully synthesized. The ${\gamma}_c$ values were analyzed by a Zisman plot, a Young-$Dupr\acute{e}$-Good-Girifalco plot, and a log ($1+cos{\theta}$) vs log ${\gamma}_L$ plot. The ${\gamma}_s$ value of BPDA-BAPE polyimide was evaluated using the geometric mean equation and our multiple regression analysis. The calculated values of ${{\gamma}_s^d$ (a dispersion component), ${{\gamma}_s^p$ (a polar component), ${{\gamma}_s^h$ (a hydrogen bonding component), and ${\gamma}_s$ were 30.79, 9.32, 0.20, and 40.31 $mN{\cdot}m^{-1}$, respectively. The ${\gamma}_s$ of BPDA-BAPP polyimide containing both a methylene group and an ether group was larger than that of the polyimide containing only a methylene group.

• 한국소음진동공학회논문집
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• 제12권9호
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• pp.731-737
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• 2002

Nonlinear vibration of the CRT shadow mask with impact damping wires is analyzed in consideration of the mask tension distribution and the effect of wire impact damping. A reduced order FEM model of the shadow mask is obtained from dynamic condensation of the mass and stiffness matrices, and damping wire is modeled using the lumped parameter method to effectively describe its contact interactions with the shadow mask. The nonlinear contact-impact model is composed of spring and damper elements, of which parameters are determined from the Hertzian contact theory and the restitution coefficient, respectively. The analysis model of the shadow mask with damping wires is experimentally verified through impact tests of shadow masks performed in a vacuum chamber.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.460-465
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• 2002

The nonlinear vibration of the CRT shadow mask is analyzed in consideration of the V-shaped tension distribution and the effect of wire impact damping. The reduced order FEM model of the shadow mask is obtained from dynamic condensation for the mass and stiffness matrices. Damping wire is modeled using the lumped parameter method to effectively describe its contact interactions with the shadow mask. The nonlinear contact-impact model is composed of spring and damper elements, of which parameters are determined from the Hertzian contact theory and the restitution coefficient, respectively. The analysis model of the shadow mask with damping wires is experimentally verified through impact tests of shadow masks performed in a vacuum chamber. Using the validated analysis model of the shadow mask with damping wires, the‘design of experiments’technique is applied to search fur the optimal damping wire configuration so that the vibration attenuation of the shadow mask is maximized.

• 한국정밀공학회지
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• 제16권4호통권97호
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• pp.197-204
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• 1999

The boundary element method was used for studying singularities of an interface crack with contact zones. The iterative procedure is applied to estimate the contact zone size. Because the contact zone size was extremely small in a tension field, a large number of Gaussian points were used for numerical integration of the Kernels. Stress extrapolation method and J-integral were used ofr determining stress intensity factors. When the interface crack was assumed to have opened tips, oscillatory singularities appear near the tips of the interface crack. But the interface crack with contact zone which Comninou suggested had no oscillatory behavior. The contact zone size under shear loading was much larger than that under tensile. The stress intensity factors computed by stress extrapolation method were close to those of Comninou's solution. And the stress intensity factor evaluated by J-integral was similar to that by stress extrapolation method.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.491-494
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• 2002

To assess the electrostatic interaction of surfaces at the triple contact line, the electrostatic field is analyzed by using the finite element method. The Helmholtz free energy is used as a functional which should be minimized under an equilibrium condition. The numerical results are compared with the nonlinear analytical solution for a two-dimensional charged interface and linear solution for a wedge shaped geometry, which shows fairly good agreement. The method is applied to the analysis of electrostatic influence on the contact angle on a charged substrate. The excess free energy found to increase drastically as the contact angle approaches to zero. This excess free energy Plays an opposite role to the Primary electrocapillary effect, as the contact angle gets smaller. This enables an alternative explanation for the contact-angle saturation phenomenon occurring in electrical control of surface tension and contact angle.