• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.525-526
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• 2006

The products designed by human sensibility and ergonomics are given good impression. Especially the touch feeling on the human skin is very useful sensibility for quality of products. Elasticity and viscosity of human skin is very important element in product design based on ergonomics. In this paper, we describe a sophisticated method for measurement of dynamic viscoelasticity characteristics of human skin. For this measurement, we developed a measurement system assembled with load cell, actuator, amplifier and data acquisition system. The $MATLAB^{TM}$ is used to analyze the data and fit a approximation curves.

• Journal of Welding and Joining
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• 제24권2호
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• pp.57-63
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• 2006

In this study, the curing kinetics and thermal degradation of underfill were investigated using differential scanning calorimetry (DSC) and thermo gravimetry analysis (TGA). The mechanical and thermal properties of underfill were characterized using dynamic mechanical analysis (DMA) and thermo-mechanical analysis (TMA). Also, we presented on underfill dispensing process using Prostar tool. The non-isothermal DSC scans at various heating rates, the exothermic reaction peak became narrower with increasing the heating rate. The thermal degradation of underfill was composed of two processes, which involved chemical reactions between the degrading polymer and oxygen from the air atmosphere. The results of fluidity phenomena were simulated using Star CD program, the fluidity of the underfills with lower viscosity was faster.

• Elastomers and Composites
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• 제50권1호
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• pp.49-54
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• 2015

Dynamically vulcanized PMMA/ACM (80 wt%/20 wt%) blend using DCP as a curing agent was prepared using internal mixer. The morphology, mechanical properties, optical properties, melt viscosity and die swell were characterized by using FE-SEM, tensile test, Izod impact test, dynamic mechanical analysis, ARES and capillary rheometer, respectively. The blends show a phase-separated morphology in which ACM are dispersed in PMMA matrix. Dynamically vulcanized blend exhibits higher mechanical properties, higher melt viscosity, and die swell as compared to simple blend. And, the dynamically vulcanized blend showed total transmittance of more than 75% and haze of higher than 90%, which enable it to find potential applications to fabricate an optical diffuser by extrusion process.

• 한국분무공학회지
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• 제15권4호
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• pp.163-169
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• 2010

Jetting stability is the most important factors in inkjet printing because printing quality is totally determined by shape of the droplets on the substrate. In order to acquire stable jet, viscosity and dynamic behavior of the ink must be considered. In addition, waveform to drive the inkjet printhead is also to be controlled. In this study, the driving waveform composed of rising time, dwell time and falling time is optimized to obtain a stable jetting using drop watcher system. Also, effect of ink viscosity on jetting is experimentally investigated by changing the temperature of ink cartridge. As a result, jetted drop having uniform velocity is acquired.

• Tribology and Lubricants
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• 제24권5호
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• pp.241-249
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• 2008

This paper describes the tribological effects on the nonlinear behavior of a spur gear pair with one-way clutch according to the direct contact elastic deformation model over a wide range of speeds, considering the hydrodynamic effects. The effects of various lubrication parameters, such as viscosity, film width, and friction, on the nonlinear dynamic behavior were analyzed. Forces due to the entraining velocity and the hydrodynamic friction were about two orders smaller than normal forces over the whole speed range. While the viscosity has a strong effect on the behavior of gear pair systems, friction has very little effect on torsional behavior. The inclusion of the hydrodynamic effect facilitates nonlinearity by increasing the overlap and damping, as well as decreasing elastic deformation and tooth reaction forces.

• Bulletin of the Korean Chemical Society
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• 제6권1호
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• pp.45-50
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• 1985

The glass transition temperature, dynamic shear moduli, and bulk viscosities of PVC, filled with nickel particles, were investigated. The glass temperature of the composite increased with increasing filler concentration. The data were interpreted by assuming that the interaction between filler particles and the polymer matrix reduces molecular mobility and flexibility of the polymer chains in the vicinity of the interfaces. The relative modulus for the PVC/Ni composite system followed the Kerner equation. The relative viscosities were strongly temperature dependent and did not agree with the conventional viscosity predictions for suspensions. It is suggested that the filler has a twofold effect on the viscosity of the composite materials; one is due to its mechanical presence and the other is due to modification of part of the polymer matrix caused by interaction. This phenomenon is approximately bounded by Kerner's predictions for suspensions.

• 한국분무공학회지
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• 제24권2호
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• pp.66-72
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• 2019

Diesel vehicles suffer from poor starting and running problems at cold temperatures. Diesel vehicles have the characteristic that CO and PM are reduced or similarly discharged when going from low temperature to high temperature. In this study, a bypass type piezo injector for electronic control based common rail injection system was used. Numerical analysis using injector drive analysis model was performed to analyze injector drive and internal fuel flow characteristics according to fuel temperature change. The results show that the rate of density change due to the fuel temperature is proportional, and that the effect of the kinematic viscosity is relatively large between $-20^{\circ}C$ and $0^{\circ}C$. Comparing the results of temperature condition at $0^{\circ}C$ and $20^{\circ}C$, it is considered that the viscosity is more correlated with the needle displacement than the pressure chamber of the delivery chamber.

• Food Science and Biotechnology
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• 제16권1호
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• pp.146-149
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• 2007

Dynamic rheological properties of hot pepper-soybean paste (HPSP) mixed with xanthan gum were evaluated at different gum concentrations (0.3, 0.6, and 0.9%) and fermentation times (12 and 24 week). Magnitudes of storage (G') and loss moduli (G") in the HPSP-xanthan gum mixture systems increased with an increase in frequency ($\omega$), while complex viscosity (${\eta}^*$) decreased. G' values were higher than the G" values over most of the frequency range (0.63-63 rad/sec), and were frequency-dependent. The dynamic moduli (G', G", and ${\eta}^*$) of the HPSP-xathan mixtures were lower than those of the control (0% gum). The differences between the dynamic moduli values at 12-week and 24-week fermentation decreased with increasing gum concentration, showing that xanthan gum can be used to stabilize and improve the viscoelastic rheological properties of HPSP. The G' value of the HPSP-xathan mixtures increased with an increase in gum concentration from 0.3 to 0.9%, whereas the G" decreased. The ability of xanthan gum to increase the elastic properties in the HPSP-xanthan mixture systems seemed to be the result of the incompatibility phenomena existing between xanthan gum and glutinous rice starch.

• Journal of Mechanical Science and Technology
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• 제17권6호
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• pp.844-853
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• 2003

In this paper, a dynamic analysis of the reciprocating compression mechanism of a small refrigeration compressor is performed. In the problem formulation of the mechanism dynamics, the viscous frictional force between the piston and the cylinder wall is considered in order to determine the coupled dynamic behaviors of the piston and the crankshaft. Simultaneous solutions are obtained for the equations of motion of the reciprocating mechanism and the time-dependent Reynolds equations for the lubricating film between the piston and the cylinder wall and for the oil films on the journal bearings. The hydrodynamic forces of the journal bearings are calculated by using a finite bearing model along with the Gumbel boundary condition. A Newton-Raphson procedure is employed in solving the nonlinear equations for the piston and crankshaft. The developed computer program can be used to calculate the complete trajectories of the piston and the crankshaft as functions of the crank angle under compressor-running conditions. The results explored the effects of the radial clearance of the piston, oil viscosity, and mass and mass moment of inertia of the piston and connecting rod on the stability of the compression mechanism.

• 대한기계학회논문집
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• 제14권6호
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• pp.1509-1514
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• 1990

본 연구에서는 비압축성 유체가 온도의 영향을 받아 변화하는 경우에 대한 시 일링 간극내에서의 압력분포를 유한차분법을 이용하여 해석하였다. 여러기서 얻어진 결과를 이용하여 시일의 축력과 모멘트를 해석함으로써 시일의 동적 불안정성에 대하 여 논하였다. 이 때 기계평면시일의 형상은 코닝이 있고, 시일의 중심축이 경사진 경우를 고려하였다.