• Journal of the Korean Ceramic Society
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• v.34 no.12
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• pp.1254-1260
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• 1997

Influence of applied electric field on the low temperature degradation of 3 mol% YaO3 stabilized tetragonal zirconia polycrystals(3Y-TZP) was investigated using X-ray diffractometry of specimens aged under the dc field of 1.1 kV/mm in silicone oil both of 12$0^{\circ}C$-21$0^{\circ}C$. After the aging, the tetragonal to monoclinic phase transformation was observed only on the specimen surface of 3Y-TZP faced to the anode. This indicated that the surface was overcrowded with oxygen ions as a result of diffusion of oxygen vacancies toward the cathode-sided surface. To elucidate an influence of the applying time of the electric field on the extent of the degradation of 3Y-TZP in air, specimens were aged fore 0-2 hours under the electric field in the oil bath of 12$0^{\circ}C$ and then subsequently aged for 3h at 22$0^{\circ}C$ in air. The longer the specimens were aged under the field, the more extensive the transformation to the monoclinic phase was on the specimen surface faced to the cathode, probably originated from a high diffusion rate of oxygen ions due to a steep oxygen vacancy concentration gradient.

• Journal of the Korea Institute of Military Science and Technology
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• v.6 no.4
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• pp.124-131
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• 2003

When a secondary gaseous flow is injected vertically into a supersonic flow through circular nozzle, a complicated structure of flow field is produced around the injection area. The interaction between the two streams produces a strong bow shock wane on the upstream side of the side-jet. The results show that bow shock wave and turbulent boundary layer interaction induces the boundary layer separation in front of the side-jet. This study is to analyze the structure of flow fields and distribution of surface pressure on the flat plate according to total pressure ratio using a supersonic cold-flow system and also to study the control force of affected side-jet. The nozzle of main flow was designed to have Mach 2.88 at the exit. The injector has a sonic nozzle with 4mm diameter at the exit of the side-jet. In experiments, The oil flow visualization using a silicone oil and ink was conducted in order to analyze the structure of flow fields around the side-jet. The flow fields are visualized using the schlieren method. In this study, a computational fluid dynamic solution is also compared with experimental results.

• Journal of the Korean Society of Clothing and Textiles
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• v.10 no.1
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• pp.105-111
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• 1986

본 연구에서는 연신정도가 다른 완전배향사(FDY)와 부분배향사(POY)를 열처리시켜 내부구조변화를 유도한 후 염색성을 연구하였고, 염색성과의 관련성을 위해 결정화도 및 복굴절룰을 조사하였다. 열처리는 silicone oil속에서 정장상태로 실시하였으며, 시료의 염색은 Disperse Yellow 42를 이용해 무한염욕상태에서 실시하였다. 그리고, DMF를 이용해 염료를 추출시킨후 spectrophotometer 로 염료흡착량을 측정하였다. 결정화도는 밀도-결정화도 관계식으로 구하였으며, 복굴전률은 편광현미경으로 시료의 두께와 retardation을 측정한 후 계산하였다. FDY와 POY 필라멘트사의 염색성은 열처리시 감소하였으며 POY의 염색성이 FDY보다 우수했다. 결정화도는 열처리시 증가하였으며 열처리되지 않은 POY가 열처리되지 않은 FDY에 비해 낮은 값을 나타냈다. 복굴절률은 열처리시 증가하였으며 열처리되지 않은 POY가 열처리되지 않은 FDY에 비해 낮은 값을 나타냈다. 열처리후에도 POY가 FDY보다 낮은 복굴절률을 나타낸 반면 결정화도는 열처리된 POY가 열처리된 FDY와 비슷한 값을 나타냈다. 염색성은 결정화도와 배향도에 부적인 상관관계 즉 결정화도와 배향도가 증가함에 따라 염색성은 감소하는 관계를 시사했다.

• Tribology and Lubricants
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• v.14 no.2
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• pp.1-9
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• 1998

The electrorheological (ER) behavior of suspensions in silicone oil of phosphated cellulose particles (average particle size 17.77 ${\mu}{\textrm}{m}$) was investigated at room temperature with electric fields up to 2.5 KV/mm. In this paper, for development of anhydrous ER suspensions using at wide temperature range, we would like to know fundamental understandings on the ER activity. As a first step, the anhydrous ER suspensions dispersed the phosphated cellulose particles were measured, and not only the electrical characteristics such as dielectric constant, current density and electrical conductivity but also the rheological properties on strength of electric field and quantity of dispersed phase were studied. From the experimental results, the anhydrous ER suspensions dispersed phosphated cellulose particles showed a stable current density and very high performance of ER effect $(\tau/\tau_0=1030)$ on the 2.5 KV/mm and the dynamic yield stress $(\tau_y)$ was in exponential proportion to the strength of electric fields.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.345-346
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• 2002

The electrical and rheological properties of a chitosan malonate suspension in silicone oil was investigated by varying the electric fields, volume fractions of particles, and shear rates, respectively. The chitosan malonate susepnsion showed a typical electrorheological (ER) response caused by the polarizability of an amide polar group and shear yield stress due to the formation of multiple chains upon application of an electric field. The shear stress for the suspension exhibited a linear dependence on the volume fraction and an electric field power of 1.88. On the basis of the results, the newly synthesized chitosan malonate suspension was found to be an anhydrous ER fluid.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.207-212
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• 2001

Electro-Rheological(ER) fluid are suspensions which show an abrupt increase in rheological properties under electric fields. ER effects arise from electrostatic forces between the starch particles dispersed in the electrically insulating silicone oil, induced when an electric field is applied. Yield stress of the fluids were measured on the couette cell type rheometer as a function of electric fields. This paper presents performance analyses of four types of the two parallel-plate. Which have different electrode length and width but same electrode area. On the basis of the pressure drop and flow rate analysis. Four types of the two parallel-plate are designed and manufactured. Using ER fluid, it is possible to directly interface between electric signals and fluid power without moving parts.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.6
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• pp.52-64
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• 1996

This paper presents an active position control of a single-rod cylinder system featuring an electrorheological(ER) fluid-based valve. The ER fluid consisting of silicone oil and chemically treated particles is firstly composed and its Bingham property is tested as a function of imposed electric field. A multi-channel plate type of ER valve is then designed and manufactured on the basis of the field-dependent Bingham model. Performance test of the ER valve is undertaken by evaluating pressure drop with respect to the number of electrode as well as the intensity of the electric field. Subsequently, the ER valve-cylinder system is constructed and its governing equation of motion is derived. A neural control scheme for position control of the cylinder is formulated by incorporating proportional-plus-derivative(PD) controller and implemented. Experimental results of both regulating and tracking control responses are presented in order to demonstrate the efficacy of the proposed ER valve-cylinder control system.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.6
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• pp.1-11
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• 1998

This paper presents performance analyses of three types of the cylindrical-type ER(electro-rheo-logical) valves, which have different electrode length and width but same electrode area. Following the composition of silicone oil-based ER fluid, the field-dependent yield stresses are obtained from experimental investigation on the Bingham property of the ER fluid. The ER valve which is dependent on the applied electric field is devised and its theoretical model is derived. On the basis of the pressure-drop analysis, three types of the ER valves are designed and manufactured. After experimentally evaluation field-dependent pressure drops, PI controller is formulated to achieve tracking control on desired pressure drop. The controller is then experimentally implemented and tracking control performance is presented in order to demonstrate superior controllability of the ER valve. In addition, the response characteristic of the ER valve with respect to the excitation frequency of the electric fiedls is provided to show the feasibility of practical application.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2000.11a
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• pp.77-80
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• 2000

In order to determine what influences the interfacial charge in EPDM/XLPE laminates, We used PEA (pulsed electroacoustic) method. Interfacial properties such as space charge accumulation and breakdown strength in crosslinked polyethylene (XLPE)/ethylene-propylene-diene monomer (EPDM) laminates were investigated. Interfacial charge develops when the EPDM is laminated with XLPE. It showed the positive polarity same as the simulation in case on intercase of EPDM/XLPE. In case of coupling agent added silicone oil, as increasing the content of coupling agent, the interfacial charge decreased. Details of the results are given and their origins discussed.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.323-329
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• 2004

The electrical and rheological properties pertaining to the electrorheological (ER) behavior of chitosan derivatives, chitosan, chitosan ammonium salt and chitosan phosphate suspensions in silicone oil were investigated. Chitosan derivative suspensions showed a typical ER response (Bingham flow behavior) upon application of an electric field. However, chitosan phosphate suspension exhibited an excellent shear yield stress compared with chitosan and chitosan ammonium salt suspensions. The difference in behavior results from the difference in the conductivity of the disperse phases due to the difference of their polarizability. The shear stress for the chitosan, chitosan ammonium salt and chitosan phosphate suspensions exhibited a linear dependence on the volume fraction of particles and 1.18 ,1.41 and 1.67 powers of the electric field. On the basis of the experimental results, the newly synthesized chitosan derivative suspensions found to be an ER fluid.