• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1135-1138
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• 2003

ERFs(Electrorheological Fluids) arc a complex system consisting of polarizable particles and insulation liquid. When an external electric field is applied to ERFs, its apparent viscosity increases dramatically. This phenomenon is called the ER effect. Generally, the behavior of ERFs has been modeled on those of Bingham fluids. But the behavior of ERFs differs from those of Bingham fluids in many respects. In the paper, ER effect concerning flow mode of ERFs is analyzed experimentally. According to several flow conditions, the change of ER effect is presented and visualized. A new modeling methodology of ER effect to reduce the modeling error is presented.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.503-506
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• 2002

Electrorheological fluids(ERFs) show a rapid and reversible increase in viscosity by applied electric field. It is called the electrorheological effect (ER effect). The reason for ER effect is the induction of an electric dipole in each particle, leading to the formation of clusters in the direction of the field, which resist fluid flow. Generally, the behavior of ER fluids has been modeled on those of Bingham fluids. But there are some differences between Bingham fluids and ER fluids. The visualization of ER fliuds are presented and ER effects by the forming, growing and breaking of clusters are discussed. In the low shear rate area, the pressure drop is measured by a pressure sensor and the formation of ER particles is visualized by video camera. The reason for the nonlinear behavior of ER fluids at low shear rate is explained through results of visualization.

• Tribology and Lubricants
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• v.18 no.1
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• pp.16-23
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• 2002

For increasing the yield stress of ER fluids, the compressing ER electrode was developed and the compressing electrorheological (ER) behavior of anhydrous ER fluids in silicone oil of phosphorous ester cellulose powder was investigated. Under constant electric field, not only the current density but also the yield stress of anhydrous ER fluids were studied as varying the compressing length of ER electrode distance. From the experimental results the compressing of ER electrode had a large influence to the ER properties of anhydrous ER fluids. The current density was proportional to the compressing length of ER electrode under constant electric field and volume fraction also tile compressing yield stress was proportional to the volume fraction of dispersed particles under constant electric field and compressing length. When the ER electrode was compressed with 150mm after charging the electric field, 4 kV, tile yield stress of phosphoric ester cellulose ER fluids increased to thirteen times comparing with the yield stress measured at normal electrode.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.138-145
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• 2001

For increasing the yield stress of ER fluids, the compressing ER electrode was developed and the compressing electrorheological (ER) behavior of anhydrous ER fluids in silicone oil of phosphorous ester cellulose powder was investigated. Under constant electric field, not only the current density but also the yield stress of anhydrous ER fluids were studied as varying the compressing length of compressing ER electrode. From the experimental results, the compressing of ER electrode had a large influence to the ER properties of anhydrous ER fluids. The current density was proportional to the compressing length of ER electrode under constant electric field and volume fraction also the compressing yield stress was proportional to the volume fraction of dispersed particles under constant electric field and compressing length. When the ER electrode was compressed with 150mm after charging the electric field, 4 kV, the yield stress of phosphoric ester cellulose ER fluids increased to thirteen times comparing with the yield stress measured at normal electrode.

• Tribology and Lubricants
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• v.14 no.3
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• pp.7-16
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• 1998

The electrorheological (ER) behavior of suspensions in silicone oil of phosphoric ester cellulose powder (average particle size: 17.77 $\mu$m) was investigated at room temperature with electric fields up to 2.5 KV/mm. For development of anhydrous ER suspensions using at wide temperature range, we aimed to know the effect of activation of phosphoric ester cellulose particles on the ER activities. As a first step, the anhydrous ER suspensions mixing with the phosphoric ester cellulose particles which were treated with 2M phosporic acid and 4M urea were measured. After activating the anhydrous ER suspensions at 12$0^{\circ}C$, not only the analysis of dispersing cellulose particles which were reacted by phosphoric ester but also the electrorheological characteristics of ER suspensions such as dielectric constant, current density, electrical conductivity and rheological properties were studied. From the experimental results, the activation of phosphoric ester cellulose particles had an influence on the ER properties of anhydrous ER suspensions. As the activation time went by, the size and number of dispersing particles, the electrical properties and the initial apparent viscosity $(η_0)$ of ER suspensions were increased till the activation time passed 5 hours. Also, it was possible, the electrorheological effect $($\tau$/$\tau$_0)$ of ER fluids was grown by the activation of phosphoric ester cellulose particles.

• Tribology and Lubricants
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• v.15 no.3
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• pp.240-247
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• 1999

The electrorheological (ER) behavior of suspensions in silicone oil of phosphoric ester cellulose particles (average particle size : 18$\pm$1${\mu}{\textrm}{m}$) coated with octadecylamine ( $C_{18}$ $H_{37}$ N $H_2$) as surfactant was investigated at room temperature. For development of anhydrous ER suspension using at real application, it should be researched how can reduce deposition of ER particles in ER suspension. Anhydrous ER suspensions mixing with phosphoric ester cellulose particles coated with octadecylamine were measured. As increasing the coating concentration of octadecylamine, not only analysis of electrical properties such as dielectric constant, current density and electrical conductivity but also rheological properties of ER suspensions were studied. From the experimental results, coating concentration of surfactant had large influence to ER properties of anhydrous ER suspension. Current density, conductivity and electrorheological effect ($\tau$/$\tau$$_{0}$) of ER suspension were linearly reduced with increasing the coating concentration of octadecylamine. But ER suspensions dispersed the phosphoric ester cellulose particles coated with octadecylamine showed reducing deposition of ER particles and could be redispersed easily.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.157-162
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• 2003

This Paper presents a robust design of an Electrorheological(ER) damper using Taguchi method. Taguchi method is a robust design method that determines control parameters in the presence of noise effect. Electrode length, electrode gap, base oil viscosity and the weight ratio of ER particles are chosen for the control parameters and the temperature is considered to be a noise factor. The sensitivity of each factor with signal-to-noise(S/N) ratio and analysis of variance are investigated. The analysis results show that the electrode length and base oil viscosity of the ER fluid mostly affect the damping force in the absence of electric field. On the other hand, when the voltage is applied to the ER damper, the electrode length and the weight ratio of ER fluid exhibit significant effect. Based on the Taguchi method, an optimal configuration was designed and the robustness of the designed ER damper was validated by comparing the analysis and experimental results.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.12
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• pp.1684-1691
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• 2001

Electrorheological fluids(ERFs) show a rapid and reversible increase in apparent viscosity by applied electric field. It is called the electrorheological effect (ER effect). The reason for ER effect is the induction of an electric dipole in each particle, leading to the formation of clusters in the direction of the field, which resist fluid flow. Generally, the behavior of ER fluids has been modeled on those of Bingham fluids. But there are some differences between Bingham fluids and ER fluids. The visualization of ER fliuds are presented and ER effects by the forming, growing and breaking of clusters are discussed. In the low shear rate area, the pressure drop is measured by a pressure sensor and the formation of ER particles is visualized by video camera. The reason for the nonlinear behavior of ER fluids at low shear rate is explained through results of visualization. As result, the behavior of ER fluids is nonlinear at low shear rate with overshoot area because it is different to from the clusters according to the strength of electric field. The gap of electrodes becomes narrow because of the cluster layer occurrence near to electrodes in any conditions.

• The Korean Journal of Rheology
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• v.10 no.3
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• pp.143-151
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• 1998

실리콘 오일에 인산처리 셀룰로오스 분말을 분산시킨 비수계 전기유변성(ER) 유체 의 전기유변 거동을 상온에서 최대 2.5KV/mm의 전기장하에서 실험하였다. 넓은 온도 영역 에서 사용이 가증한 비수계 ER 유체를 개발하기 위해 셀룰로오스의 인산 에스테르 반응이 ER 유체의 전기유변효과에 미치는 영향을 조사하였다. 먼저 여러 가지의 인산처리 농도로 처리된 인산처리 셀룰로오스 미립자를 분산시킨 ER 유체를 제조한 후 ER 유체의 유전상수, 전류밀도 및 전기전도도 등과 같은 전기적 특성을 측정하였으며 ER 유체의 전기유변 특성 또한 측정하였다. 인산처리 셀룰로오스가 분산된 비수계 ER 유체의 전류밀도는 셀룰로오스 의 인산 에스테르 반응에서의 인산처리 농도에 의해 조절할수 있음을 알수있었으며 셀룰로 오스의 인산처리 농도가 2.5 M과 3.0 M 사이일 때 인산처리 셀룰로오스가 첨가된 비수계 ER 유체의 전기유변효과 ($\tau$/$\tau$0)가 가장 높게 측정되었다.

• Tribology and Lubricants
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• v.15 no.1
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• pp.8-16
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• 1999

The electrorheological (ER) behavior of suspensions in silicone oil of phosphoric ester cellulose powder (average particle size : 18$\pm$1 ${\mu}{\textrm}{m}$) was investigated on the elevated temperature up to 10$0^{\circ}C$. For development of anhydrous ER fluids using at wide temperature range, it should be researched to how the effect of temperature on the ER activities. As a first step, the anhydrous ER suspensions mixing with the phosphoric ester cellulose particles which were made from the phosphoric ester reaction of cellulose were measured. As increasing the temperature, not only the analysis of electrical properties such as dielectric constant current density and electrical conductivity but also the rheological properties of ER fluids were studied. From the experimental results, the temperature had a large influence to the ER properties of anhydrous ER fluids. The current density, conductivity and elecoorheological effect ($\tau$$_{A}$$\tau$$_{0}$) of phosphoric ester cellulose ER fluids were proportional to the temperature with power law. And the shear stress of them was closely related with the square of dielectric constant mismatch parameter ($\beta$$^2$) under constant shear rate and electric field.d.