• 한국세라믹학회지
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• 제49권6호
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• pp.542-548
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• 2012

The viscosity of a ceramic slurry depends on the slurry concentration, particle shape and size, hydrodynamic interactions, temperature, shear rate, pre-treatment condition and the method of measurement with the selected equipment. Representative ceramic slurries with low to high viscosity levels are selected from colloidal silica, barium titanate slurry and glass frit paste. Rotational rheometers and vibrational viscometers are used to compare the measured viscosity for various ceramic slurries. The rotational rheometer measured the viscosity according to the change of the shear rate or the rotational speed. On the other hand, the vibrational viscometer measured one point of the viscosity in a fixed vibrational mode. The rotational rheometer allows the measurement of the viscosity of a ceramic paste with a viscosity higher than 100,000 cP, while the vibrational viscometer provides an easy and quick method to measure the viscosity without deformation of the ceramic slurry due to the measurement method. It is necessary to select suitable equipment with which to measure the viscosity depending on the purpose of the measurement.

• Tribology and Lubricants
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• 제14권2호
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• pp.42-48
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• 1998

Electro-Rheological (ER) fluid is a class of functional fluid whose apparent viscosity can be varied by the applied electric field strength. The ER fluid is classified into two types; one is a dispersive fluid and the other is a homogeneous. Dispersive ER fluid is a colloidal suspension of fine semiconducting particles in a dielectric liquid and liquid crystal (LC) is classed as homogeneous type ER fluid. LC has been originally developed for some electronic display devices. Various mechanical components applying ER fluid have been developed, and the their performance typically depends on the characteristics of ER fluid which have generally been evaluated by a rotational viscometer. However, the ER fluid introduced into various mechanical components undergoes not only simple shear flow but press flow or oscillating flow. For the evaluation of ER fluid, the authors developed an reciprocating type viscometer. The amplitude is controlled on 5 mm at the frequency from 50 to 1000 Hz. In the present paper, the performance of several types of ER fluid is evaluated by the reciprocating type viscometer and compared with those evaluated by a rotational viscometer.

• 한국식품영양과학회지
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• 제28권3호
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• pp.554-558
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• 1999

Flow properties of traditional kochujang at various fermentation times(0~12 weeks) were determined with rotational cylindrical(RC) and serrated plate plate(PP) viscometer. Magnitudes of consistency index(K) of power law model and Cassson parameters(yield stress and viscosity) measured by PP viscometer were higher than those using RC viscometer. All kochujang samples during fermentation were much shear thinning with values of flow behavior index(n) as low as 0.2~0.34. K value and Casson yield stress measured by PP viscometer had good correlations(r=0.94; r=0.91) with fermentation time. No significant changes in flow model parameters measured by RC viscometer were observed for kochu jang during fermentation. Magnitudes of flow model parameters measured by PP viscometer more closely correlated with fermantation times of kochujang than did RC viscometer.

• 유변학
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• 제11권2호
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• pp.73-81
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• 1999

회전식 점도 측정기를 이용하여 상용화된 전기유변(electrorheological, ER)유체와 자기유변(magnetorheological, MR)유체의 특성을 비교하여 이를 이용한 장치 설계시 두 유체 중에 유리한 것을 선택하는데 도움이 되고자 하는 것이 본 논문의 의도이며, 이러한 유체의 특성에서 전단변형률의 변화에 따른 전단응력의 변화, 온도변화에 따른 전단응력의 변화, 작용하는 장의 세기에 따른 전단응력의 변화 등을 비교하였다. 온도의 변화에 따른 유체의 특성 변화는 MR유체가 ER유체보다 적게 받는 경향이 있었다. 두 유체의 응용 예로서 제작된 댐퍼의 경우에 유압 시험기를 이용하여 인장과 압축될 때 장의 On/Off에 따른 시간지연과 감쇄력을 비교하였다.

• 한국산학기술학회논문지
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• 제14권8호
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• pp.4028-4032
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• 2013

폐타이어 재활용을 위한 열분해 공법으로 발생하는 열분해 카본블랙의 재활용 방안이 필요하다. 아스팔트 바인더의 소성변형 특성을 개선하기 위하여 페타이어 열분해 공법의 부산물인 카본블랙을 이용하였다. 원아스팔트에 열분해 카본블랙 0%, 5%, 10%, 15% 및 20%를 혼합하였고, 연화점, 침입도시험, 회전점도계 및 동적전단유동기시험을 시행하였다. 열분해 카본블랙을 혼합한 아스팔트 바인더의 연화점은 증가하였고, 인화점은 기준값을 만족하였다. 135도에서의 회전점도값은 증가하였고, 소성변형에 대한 저항성이 개선되는 것으로 나타났다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.576-579
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• 2005

MR (Magneto Rheological) fluids are well known as a smart fluid and their application researches to control vibration have been conducted by many researchers. However, their dynamic properties have not been identified clearly yet. Therefore, the MR effect is investigated by using a rotational viscometer and a single degree of freedom system with an MR damper. The results obtained from the experimental study show that stiffness and viscous damping coefficients of the system with an MR damper are changed according to the variation of the applied current.

• Bulletin of the Korean Chemical Society
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• 제3권3호
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• pp.83-88
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• 1982

Viscosity and zeta-potential of 11.0 wt. % aqueous bentonite suspension containing various electrolytes and hydrogen-ion concentration were measured by using a Couette type automatic rotational viscometer and Zeta Meter, respectively. The effects of pH and elcctrolytes on the rheological properties of the suspension were investigated. A system, which has a large zeta-potcntial, has a small intrinsic relaxation time ${\beta}$ and a small intrinsic shear modulus $1/{\alpha}$ in the Ree-Eyring generalized viscosity equation, i.e., such a system has a small viscosity value, since ${\eta}={\beta}/{\alpha}$. In general, a stable suspension system has large zeta-potential. The stability condition of clay-water suspension can be estimated by viscometric method since stable suspension generally has small viscosity. The correlation between the stability, viscosity and zeta-potential has been explained by the Ree-Eyring theory of viscous flow.

• Bulletin of the Korean Chemical Society
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• 제4권5호
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• pp.212-217
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• 1983

Depending on the range of shear rates, temperatures and concentrations, the potato starch suspension in water behaves as a typical dilatant system. The flow curves of the suspension at various concentrations and temperatures were obtained by using a Couette type rotational viscometer. The flow mechanism of the suspension is explained by a structure model of starch granules in the suspension. Based on the experimental results, a general flow equation for the dilatant system is proposed. By analyzing the temperature dependency of the relaxation time, the activation enthalpy and activation entropy for flow in the starch-water suspension were calculated, the former being about 10 kcal/mol.

• 한국해양학회지:바다
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• 제4권4호
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• pp.390-399
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• 1999

북동태평양 심해저 생물자원 퇴적물에서 서로 다른 두 종류의 측정기 그리고 선상 및 육상 실험실에서 획득한 베인전단강도(vane shear strength) 자료의 비교 연구를 위하여 다중주상시료 채취기(multiple corer)로 규질 및 탄산질 퇴적물 시료를 채취하였다. 전단강도는 $2.0{\times}2.0$ cm의 베인($90^{\circ}$ four blade vane)이 장착된 수동베인측정기(hand-held vane apparatus, 수동베인) 그리고 회전식 점도계 (rotational viscometer)에 $1.0{\times}0.88$ cm의 베인을 장착하여 구성한 전동베인 측정기(motorized shear vane system, 전동베인)로 측정되었다. 수동베인과 전동베인으로 측정된 전단강도 값들은 코어 깊이에 따라 증가하는 동일한 변화 양상을 보이며, 절대 값도 유의한 차이를 보이지 않는다. 그리고 선상에서 측정된 전단강도 값에 비하여 3개훨월후 실험실에서 동일 장비에 의해 측정한 값들 또한 큰 차를 나타내지 않는다. 한편, 실험실에서 전동베인으로 동일한 코어를 2~4회 반복 측정한 결과 동일한 깊이에서도 측정 지점(hole)에 따라 차이가 나타난다. 또한 한 정점 내에서 서로 다른 코어 시료중 전단강도 값은 상당한 차이를 보이는 경우도 있다. 이는 심해저 주상 퇴적물의 물리적 특성이 생물 교란 작용 등의 영향으로 국부적으로 다르기 때문에 나타난 결과로 판단된다. 즉 심해저 퇴적물의 전단강도는 선상에서 또는 3개월이 지난 후 실험실에서, 그리고 두 종류의 기기를 사용하여도 깊이에 따른 유의한 차이를 보이지 않고, 오히려 한 코어시료 내의 국부적 물성차이 또는 한 정점 내 지점별 물성차이에 의한 변화 폭이 더 크게 나타낸다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2003년도 학술대회지
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• pp.229-234
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• 2003

As electrorheological fluid(ER fluid) has a characteristic that apparent viscosity varies when electric field applied, so rheological characteristic(yield stress & viscosity) changes in proportion to the electric field applied and the response time is very short within a few miliseconds . In case of using ER fluid for journal bearing as lubricant, it is estimated that it's possible to realize very effective journal bearing system that is not complicate and has a very quick response time. It is necessary to examine the influence of rheological characteristic that varies with electric field applied on bearing characteristic to apply ER fluid to journal bearing, however there are few studies for about that. As for the journal bearing, it comes under high shear flow mode that has shear rate range of $10^3\~10^4s^{-1}$ because rotational speed is very high and clearance is small. But most of the studies for about ER fluid issued until now is about the range of $10\~10^2s^{-1}$. So, there are a lot of difficulties to understand the characteristic offish shear flow mode and furthermore it is restricted to make an experiment for about the characteristic of ER fluid because of the limitation of experimental equipment. The equipment was prepared to make an experiment lot high shear flow mode that has the range of $10^3\~10^4s^{-1}$ using ER fluid that is composed of silicon oil with dispersed particle of starch. Using the above system, the fluid characteristic of ER fluid was studied.