• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.103-106
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• 2004

The new rheology fabrication process has been developed to rheo die casting and rheo forming process. Thixoforming process has disadvantages in terms of induction reheating process, scrap recycling, loss of raw material and cycle time. Therefore, to reduce the number of process, new rheology fabrication process with specially designed the rotational barrel type equipment has been proposed to apply in various part productions. The barrel type equipment, which could continuously fabricate the rheology materil, was specially designed to have a function to control cooling rate, shear rate and temperature. During the continuous rotation of barrel with a constant temperature, the shear rate is controlled with the rotation speed. The barrel surface has both the induction heating system and the cooling system to control the temperature of molten metal. By using this system, the effect of the rotation speed and the rotation time on the microstructure was widely examined. The possibility for the rheoforming process was investigated with microstructural characteristic.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.150-153
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• 2007

Apply electromagnetic stirring system to making rheology slurry of Al7075. This experiment has important element which is the relation between solid fraction percent and melt temperature of Al7075. The rheology slurry of Al7075 eliminated liquid phase to include alloying element of copper and zinc by squeeze casting process. In result the most structure was composed entirely of globular primary $\alpha$. Used this material for this study. This study made a comparison of mechanical property according to heat treatment T6 at each melt temperature ($619^{\circ}C$ and $615^{\circ}C$). The microstructure and component are observed how heat treatment T6 weight with the mechanical property by SEM-EDS.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.43-43
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• 2007

LTCC는 최근의 이동 통신 환경의 급격한 발전 속에 그 응용 및 특성 요구가 증폭되고 있다. 이러한 LTCC 소재는 주로 테이프 캐스팅에 의한 후막 공정으로 제품이 만들어지게 되는데, 캐스팅을 위해 제조되는 슬러리는 일반적으로 유변학적 의사가소성 거동을 하는 것으로 알려져 있다. 그러나, 슬러리 제조 조건에 따라 유변학적 거동이 다르게 나타나는 것이 관찰되었다. 이에, 슬러리 제조 조건을 다양하게 변화시키며, 유변학적 거동을 살며 보고 이렇게 변화된 유변학적 거동과 캐스팅된 시트 특성과의 관계를 검토해 보려 한다. LTCC 재료의 주 구성 요소인 glass와 세라믹 분말의 초기 조건 및 각각의 rheology 특성과 혼합 슬러리에서의 관계성 등을 고찰하려 한다.

• Korea-Australia Rheology Journal
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• v.17 no.4
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• pp.191-198
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• 2005

The static and dynamic rheological behavior of concentrated sodium dodecylsulfate (SDS) stabilized, deformability controllable polydimethylsiloxane (PDMS) emulsions is reported and comparisons made with silica (hard sphere) suspensions. Steady-mode measurements indicate 'hard' (viscoelastic) droplets behave as hard spheres, while 'soft' (viscous) droplets induce structural flexibility of the emulsion against shear. Dynamic-mode measurements reveal that viscoelasticity of droplets provides the great magnitude of elasticity for the 'hard' emulsion, while formation of planar films between droplets is the origin of the elasticity of 'soft' emulsions. Combination of steady and dynamic rheological behavior has enabled depiction of droplet structure evolution in relation to the shear stress applied, especially by taking advantage of the normal force that reflects the transient deformation of droplets.

• Proceedings of the Korean Society of Rheology Conference
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• 2002.11a
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• pp.159-162
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• 2002

No Abstract, See Full Text

• Korea-Australia Rheology Journal
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• v.15 no.2
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• pp.97-105
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• 2003

In the previous paper (Hyun et al.,2002), we have investigated the shape of storage modulus (G') and loss modulus (G") of complex fluids under large amplitude oscillatory shear (LAOS) flow. As the strain amplitude increases, owever, the stress curve becomes distorted and some important information may be smothered during data processing. Thus we need to investigate the stress data more precisely and systematically. In this work, we have obtained the stress data using high performance ADC (analog digital converting) card, and investigated the nonlinear response of complex fluids, 4wt% xanthan gum (XG), 2 wt% PVA/ 1 wt% Borax, and 1 wt% hyaluronic acid (HA) solutions, using Fourier transformation (FT) rheology. Comparing the strain signals in time domain with FT parameters in frequency domain, we could illustrate the sensitivity and importance of FT rheology. Diverse and unique stress patterns were observed depending on the material system as well as flow environment. It was found that they are not the outcome of experimental deficiency like wall slip but characteristics of the material system. When nonlinear response of complex fluids is analyzed, the intensity and phase angle of higher harmonic contributions should be considered together, and the shape of the stress signal was found to be strongly dependent upon phase angle.ngle.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.287-288
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• 2006

• Korea-Australia Rheology Journal
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• v.11 no.4
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• pp.321-328
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• 1999

This paper discusses the rheology of complex interfaces comprised of amphiphilic materials that are susceptible to flow-induced orientation and deformation. The consequence of the coupling of the film micro-structure to flow leads to nonlinear rheology and surface fluid dynamics. Experimental methods designed to determine the mechanical rheological material functions of fluid-fluid interfaces as well as local, molecular and morphological responses are presented. These include a newly developed interfacial stress rheometer, flow ultraviolet dichroism, and Brewster-angle microscopy. These techniques are applied to a number of complex interfaces ranging from low molecular weight amphiphiles to polymer monolayers. Nonlinear flow phenomena ranging from two-dimensional nematic responses to highly elastic surface flows that manifest surface normal stress differences and elongational viscosities are described.

• Archives of Plastic Surgery
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• v.47 no.4
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• pp.301-304
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• 2020

Dermal injectables are the most popular material for facial enhancement, including volumizing and wrinkle correction. However, although hyaluronic acid is the most common component of dermal injectables, the character of hyaluronic acid products is quite variable. These materials can be described in terms of their viscoelastic properties using four parameters. In this article, the author would like to describe these properties in detail. Although many physicians consider this material to be convoluted, thoroughly understanding the characteristics of various injectables enables us to tailor procedures accordingly and to enhance the final results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.463-466
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• 2005

The microstructure and mechanical properties of rheocast A356 aluminum alloy by electromagnetic stirring are studied. In the electromagnetic stirring, main parameters are stirring current and stirring time. Stirring current is ranged from 0 A to 60 A, and stirring time is 20, 40, and 60 sec. In the rheocasting, injection velocity and applied pressure are changed. In this paper, the effect of stirring current and stirring time on the morphology and mechanical properties are investigated and analyzed.