• The Korean Journal of Rheology
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• v.11 no.2
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• pp.82-90
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• 1999

Electrorheological(ER) fluid is a material that shows the dramatic change of rheological properties under an electric field and responds reversibly in a few milliseconds. ER fluid's response to an electric field along with its fast switching capability allows ER devices to be precisely controlled. The real application with ER fluid, however, has many limitations to be overcome; temperature fluctuation, moisture, dust, aggregation, precipitation, and low yield stress, for example. The magnitude and the characteristics of yield stress of ER fluid plays an important role in practical applications. In this research, a dynamic simulation on the squeezing flow of the ER fluid was carried out. Numerical simulation on isolated chains was performed to find out the effect of hydrodynamic and electrostatic force depending on the chain location, the squeezing rate, and the chain structure. Suspension model that is composed of a large number of particles was also investigated. The increase of normal stresses as well as the existence of a yield stress at an earlier stage could be observed, and the effective control of the normal stresses could be achieved at an optimal condition of the hydrodynamic force and the electrostatic force.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.968-971
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• 2002

Two decisive mechanisms of the electrorhological polishing for a small part(for example, a aspherical surface in a micro lens) are explained. Firstly, non-uniform electric field generated in the polishing structure increases a shear stress of ER fluids which is maximized dramatically near the tool, therefore, substrate adjacent to the tool can be removed effectively by mixed abrasives in the ER fluid. Secondly, abrasives in a non-uniform electric field are governed by the dielectrophoretic phenomena. Abrasives move toward the tool because the field gradient is highest near the tool and then abrasives are actively holded in that area. This phenomena is observed and evaluated by the optical measurement.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.6
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• pp.164-174
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• 1996

This paper presents control and response characteristics of a continuously variable ER(electrorheological) damper for small-sized vehicles. The ER damper is devised and its governing equation of motion is derived from the bond graph model. The field-dependent yield shear stresses are distilled from experimental investigation on the Bingham property of the ER fluid. The distilled data are incorporated into the governing system model and, on the basis of this model, an appropriate size of the ER damper is manufactured. After evaluating the field-dependent damping performance of the proposed ER damper, the skyhook control algorithm is formulated to achieve desired level of the damping force. The controller is then experimentally implemented and control characteristics of the ER damper are presented in order to demonstrate superior controllability of the damping force. In addition, response characteristics of the damping force with respect to the electric field with fast on-off frequency are provided to show the feasibility of practical application.

• The Korean Journal of Rheology
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• v.11 no.2
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• pp.73-81
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• 1999

The intention of this research is to give criteria of designing devices using ER fluids and MR fluids. The Properties of commercial ER fluids and MR fluids are compared using a rotational viscometer. The yield strength is compared upon changes of shear rate, temperature and applied fields. MR fluids seem less sensitive to temperature change than ER fluids. In cases of MR and ER fluid dampers, the time delay and damping force are measured in tension and compression mode when the applied field changes.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.12
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• pp.1199-1205
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• 2011

In the present work, a seat suspension system adopting semi-active damper is evaluated for driver's ride quality. A cylindrical type of ER(electrorheological) damper is designed and manufactured for the seat suspension of heavy vehicles. The governing equation is derived under consideration of human vibration. A sliding mode controller is then synthesized and experimentally realized on the manufactured ER seat suspension while a driver is sitting on the controlled seat. Ride quality is evaluated by fatigue decreased proficiency boundary, vibration dose value and crest factor utilizing weighted-acceleration according to ISO2631.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1994.06b
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• pp.3-15
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• 1994

80년대 후반들어 갑자기 새로운 가치와 가능성에 대한 조명을 다시금 받게된 ER 유체는 유선 국내에서는 물론 일본에서조차 번역에서의 정확한 명칭이 분분할 정도로 아직 국내에서는 생소한 분야이다. 이웃 일본에서는 ER 유체, 전기점성 유체, 전기레올로지 유체, 일렉트로레올로지 유체, Winslow 유체라고 불려지고 있고 우리나라에서는 전기유변성유체라고도 불리운다. ER 유체는 전장을 가함으로써 점도를 변화시킬 수 있는 콜로이드 용액의 총징으로, 절연성 유체 중에, 이러한 성질을 갖는 미분말을 분산시킨 것이다. 이 유체의 특징으로는 전장으로 점도의 변화를 제어할 수 있고, 점도를 변화 시킬 수 있는 범위가 넓고, 또한 응답성이 좋은 것에 있다. 80년대에 들어 서면서, 전자기술의 급속한 발전으로 이 ER 유체의 장점에 ER 유체의 단점을 보완할 수 있는 응답성이 빠른 전자 제어 기술의 출현은 바로 이 ER 유체의 최대 난점들을 해결할 수 있는 가능성을 제시하면서 급속한 인기를 더해 가고 있다. 이러한 배경에서 국내에서도 이분야에 대한 연구의 필요성이 대두됨에 따라 본 해설에서는 국외 논문, 국제 학술회의 논문집, 해설등을 통하여 발표된 ER 유체에 대하여 알아 보고 이를 적용한 기전요소에의 응용에 대하여 살펴보기로 한다.

• Korean Chemical Engineering Research
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• v.62 no.3
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• pp.269-273
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• 2024

The normal stress of TiO₂ ER fluid under an electric field showed negative values due to the electrostatic attraction force in the normal direction between particles and the absolute value increased dramatically with electric field strengths. The normal yield stress exhibited E² dependence similar to the dynamic yield stress, indicating that normal stress can be utilized for evaluating the ER effect. Numerical simulation demonstrated good qualitative agreement with the experimental data and suggested that the decrease in the absolute value of normal stress with increasing shear rates was attributed to the rearrangement of particle configurations under shear.

• 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.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.11
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• pp.171-178
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• 2004

This paper presents vibration characteristics of a wire cut discharge machine in which an electro-rheological brake actuator is used to control the wire tension. The ER brake actuator has several advantages including design simplicity, fast response time and real-time controllability. On the basis of the tension level required in the machine an appropriate size of the ER brake actuator is devised. The ER brake actuator is then incorporated with the machine and the field-dependent wire tension is experimentally evaluated. The straightness of the workpiece is also empirically investigated by changing the intensity of the electric field.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1298-1302
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• 2000

Electrorheological(HER) and magnetorheologica(MR) fluids have a unique ability to increase the dynamic yield stress of the fluid substantially when electric or magnetic field is applied. ER and MR fluid-based dampers are typically analyzed using Bingham-plastic shear flow analysis under Quasi-steady fully developed flow conditions. An alternative perspective, supported by measurements reported in the literature, is to allow for post-yield shear thinning and shear thickening. To model these, the constant post-yield plastic viscosity in Bingham model can be replaced with a power-law model dependent on shear strain rate that is known as the Herschel-Bulkley fluid model. The objective of this paper is to predict the damping forces analytically in a typical ER bypass damper for variable electric field, or yield stress using Herschel-Bulkley analysis.