• The Korean Journal of Rheology
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• v.10 no.1
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• pp.31-37
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• 1998

전기장이 인가되고 있는 유로를 유동하는 전기유변유체의 기본성질을 파악하기 위 한 실험 및 해석적 연구를 수행하여 빙햄유체로서의 유효성에 대해 알아보고 전기장과 유로 면 형상 및 진동유동으로 인한 영향에 대해 조사함으로써 ER밸브 및 ER대퍼로의 응용과 관련한 감쇄력 제어에 대해 검토하였다. 첫 번째 실험은 ER밸브의 높이가 2mm인 적극면이 평탄한것과 요철로 된 것을 사용하여 압력손실을 압력변환기로 측정함으로써 전기장 및 유 로형상에 대한 영향을 알아보았다. 압력손실 및 전단응력이 전기자세기와 함수관계를 가짐 을 알수 있었고 전기장세기와 유속의 변화시 손실계수에 의한 ER효과의 상이함이 확인되었 으며 레이놀즈수가 커지면 항복전단응력의 영향은 나타나지 않았다. 두 번째 실험은 실린더 를 정현파로 진동시켜 ER밸브에서 감쇠력제어가 가능한가를 알아보고 빙햄유체모델로 설계 된 ER댐퍼의 모델과 비교하였다. ER배르와 ER댐퍼의 수학적 모델을 시뮬레이션한 결과는 약간 벗어남이 보이기는 하나 실험결과와 일치하요 있다. 이것은 ER유체를 단순히 빙행유 체로 취급할수없으나 거시적으로는 빙햄유체로 취급할수 있음을 시사한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.2 no.2
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• pp.107-113
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• 2001

This work presents field-dependent Bingham and response characteristics of MR fluids under shear and flow modes. Two different types of magneto-viscometers are designed and manufactured for the shear and flow modes. respectively. For the MR fluid to be tested, MRF-132LD of Lord co. is employed. The field-dependent yield stress is experimentally distilled at various temperatures using the magneto-viscometers. Time responses of the MR fluids to step electric fields are also evaluated under two operating modes.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.6 s.165
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• pp.1055-1064
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• 1999

In this wort ER(electro-rheological) clutch and MR(magneto-rheological) clutch are devised and their performance characteristics such as response time and controllability are compared. As a first step, field-dependent yield stresses of ER and MR fluids are distilled in shear mode. For reasonable comparison between two clutches, a nondimensional design model is established by choosing same design parameters of gap size and number. Following the manufacturing of two clutches, field-dependent torque level, response time to step input, mechanical Power generation to electric power consumption are experimentally measured and compared. In addition, in order to investigate torque controllability of the clutches a sliding mode controller is formulated and experimentally realized. Control bandwidths of two clutches are identified and tracking control responses for desired torque trajectories are presented.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.3
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• pp.62-74
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• 1994

This paper addresses on the model synthesis and performance analysis of an engine mount featuring electro-rheological(ER) fluids which undergo a phase change when subjected to electric fields. A novel type of ER fluid-filled engine mount is devised and its hydraulic model is constructed. An equivalent mechanical model is subsequently obtained from the governing equation of the hydraulic model. The model parameters associated with the ER fluids are distilled from experimental investigations on the Bingham properties of the fluids. The distilled data are then incorporated into the governing model to undertake feasible work through computer simulations,. It is shown that the proposed engine mount has an inherent capability of controlling both the damping force and the resonance frequency. Other superior performance characteristics accrued from the proposed methodology are also evaluated.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.382-387
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• 2003

Many type of smart materials and control laws are available to actively adjust the structure from various external disturbances. Usually, a certain type of control law to activate a specific smart material is tell established, but the effectiveness of the control scheme is limited by the choice of the smart materials and the responses of the structure. ER fluid is adequate to provide small but arbitrary control forces at any point along the structure. It was found that active vibration control of the structure embedded with ER fluids fluidly to suppress the vibration excited with broad band frequency due to the limited change of the structure characteristics. To compensate this limited effect of the control scheme with ER fluid alone, PPF control using PZT as an actuator is added to construct a hybrid controller.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.12
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• pp.3991-4002
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• 1996

Thermally fully developed and thermally developing laminar flows of a Bingham plastic in a circular pipe have been studied analytically. For thermally fully developed flow, the Nusselt numbers and temperature profiles are presented in terms of the yield stress and Peclet number, proposing a correlation formula between the Nusselt number and the Peclet number. The solution to the Graetz problem has been obtained by using the method of separation of variables, where the resulting eigenvalue problem is solved approximately by using the method of weighted residuals. The effects of the yield stress, Peclet and Brinkman numbers on the Nusselt number are discussed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.7
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• pp.801-810
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• 1999

The purpose of present research was to get characteristics and basic knowledges of electrorheological(ER) suspension. To observe behaviors of the ER suspensions. transparent conductive plates were used to visualize the flow of ER suspensions between two parallel plate electrodes. The influence of flowing speed and intensity of electric field on the ER fluid were examined in circle-shaped electric field, and it takes several hundred milliseconds that suspensions in flow cluster. The present study also conducts a numerical analysis adopting the Bingham model. It is found that simple Bingham model can not property describe the flow behavior in the parallel plates.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.4
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• pp.148-157
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• 1994

A multi-cylindrical hydraulic valve incorporating with an electro-rheological(ER) fluid is developed in this study. Field-dependent Bingham properties of the ER fluid are exploited to devise the valve system which features fast system response as well as simple mechanism. The fast response is accrued from almost instant response characteristics of the ER fluid itself, and the mechanism configuration is simplified since no nechanically moving parts are required. The material properties of the ER fluids to be utilized for modeling of the proposed valve system are firstly tested with a couette-type electroviscometer. The design and manufacturing processes are then undertaken on the basis of model parameters. The performance characteristics of the valve system are evaluated in terms of pressure variations with respect to the intensity of employed electric fields and flow rates.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.12
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• pp.4003-4012
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• 1996

Hydro dynamically developing and simultaneously (hydro dynamically and thermally) developing laminar flows of a Bingham plastic in a circular pipe have been investigated numerically. Solutions have been obtained by using a four-step fractional method combined with an equal order bilinear finite element method. For the hydro dynamically developing flow, shorter entrance length is required to reach fully developed velocity field for larger yield stress and non-monotonic pressure drop along the pipe centerline is observed when the yield stress exceeds a certain critical value. For the simultaneously developing flow, the heat transfer characteristics show the same trends as those predicted for the thermally developing flow (Graetz problem).

• Applied Biological Chemistry
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• v.29 no.4
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• pp.339-345
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• 1986

Rheological characteristics of starch isolated from germinated corn were investigated and compared with those of nongerminated corn starch. Flow behavior of both starches were Bingham psudoplastic. Consistency index and yield stress of germinated starch solution were lower than those of nongerminated starch solution, while flow behavior index was nearly similar. Concentration dependency of both starch solutions were similar to each other but lower temperature dependency of germinated starch solution was observed. Time dependent characteristics of both starches showed thixotropic behavior, but due to germination, germinated starch showed higher structural decay under shear than nongerminated starch and its elastic properties was weaker.