• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.3
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• pp.545-553
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• 1998

Recently a new process known as the magnetic fluid grinding has been developed, which can remove material from the surface of ceramic balls by fifty to one hundred times more rapidly than the conventional lapping process. In this study, the ceramic balls with various compositions are made and ground by using the magnetic fluid grinding technique with various machining parameters. In order to make well-round shaped balls by using the magnetic fluid grinding technique, the fundamental research to find out the machining factors has been carried out. Developing an equipment with higher efficiency and reliability in the machining could certainly lead to the higher productivity with excellent quality of ceramic balls.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1289-1293
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• 2005

We will improve tools performance without the change of a tools' physical shape, if we process mirror like finishing on the surface of cutting tools. Because cutting tools' shapes are very complex, the general method of polishing can't be polished. So we will apply new method of polishing which is magnetic fluid grinding technique. Magnetic fluid grinding technique can polish complex shape's workpiece by pressing the surface of workpiece with magnetic and abrasive grains in magnetic field. Therefore we developed the polishing equipment to improve the performance of cutting tools and experimented on various polishing conditions to determine the polishing conditions of cutting tools.

• Proceedings of the Korean Magnestics Society Conference
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• 1998.10a
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• pp.110-111
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• 1998

• Proceedings of the Korean Magnestics Society Conference
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• 1995.05a
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• pp.38-39
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• 1995

• Journal of the Korean Ceramic Society
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• v.33 no.3
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• pp.269-276
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• 1996

The effect of sintering aids on the sinterability for silcion nitride has been studied by hundreds workers. However the effect of sintering aids on the machinability as the own trobles which is the major barrier for the field applications of the ceramic components has not been fully studied. in this study the contents of Al2O3 and Y2O3 in silicon nitride were varied from 0 to 8 wt% respectively. The physical and mechanical properties of the silcion nitride were measured. The optimal microstructure of silicon nitride balls with the excellent machinability by adding with various contents of sintering aids was studied by MGF(magnetic-fluid grinding)technique. An attempt to figure out how the mechanical properties influence the machinability of silicon-nitride ball was made.

• Tribology and Lubricants
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• v.31 no.2
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• pp.62-68
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• 2015

A magnetorheological (MR) fluid is a smart material whose rheological behavior can be controlled by varying the parameters of the applied magnetic field. Because the damping force and shear force of an MR fluid can be controlled using a magnetic field, it is widely employed in many industrial applications, such as in vehicle vibration control, powertrains, high-precision grinding processes, valves, and seals. However, the characteristics of friction caused by iron particles inside the MR fluid need to be understood and improved so that it can be used in practical applications. Surface process technologies such as polytetrafluoroethylene (PTFE) coatings and diamond-like carbon (DLC) coatings are widely used to improve the surface friction properties. This study examines the friction characteristics of an MR fluid with different surface process technologies such as PTFE coatings and DLC coatings, by using a reciprocating friction tester. The coefficients of friction are in the following descending order: MR fluid without any coating, MR fluid with a DLC coating, and MR fluid with a PTFE coating. Scanning electron microscopy is used to observe the worn surfaces before and after the experiment. In addition, energy dispersive X-ray spectroscopy is used to analyze the chemical composition of the worn surface. Through a comparison of the results, the friction characteristics of the MR fluid based on the different coating technologies are analyzed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.354-361
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• 2005

In high speed cutting process, due to the friction between the tool and workpiece, a temperature rise of contacting part is serious. It need to develop cutting tool for overcoming such a poor condition. So now, some studies, the optimization of tool shapes, the fine grains of tool material, multi-layer coating of tools are processing. If mirror finishing on the tool is processed, there is advantage of relation between chip and tool, because of less friction, and also tool's lift would be increased. As a result mirror like finishing is expected efficient enhancement of tool. Generally, it is too difficult to process by a general way for tools of complex shapes, it is required a new method to process such complex shape tools. The magnetic fluid polishing technique can polish the workpiece of complex shape, because the polishing method which polishes as compress the workpiece by the magnetism abrasives to arrange to the linear according to the line of magnetic force. In this paper, We polished the surface of the high speed cutting tool using the magnetic fluid polishing technique, to enhance the performance of the high speed cutting tool.

• Journal of the Korean Ceramic Society
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• v.35 no.2
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• pp.115-122
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• 1998

The effect of sintering conditions on the sinterability for silicon nitride has been studied by many in-vestigators. However the effect of sintering conditions on the machinability which is the major barrier to the field applications of the ceramic components has not been fully studied. In this study the sintering con-ditions such as temperature gas pressure and time in silicon nitride were varied. The physical and mechan-ical properties of the gas pressure sintered (GPS) silicon nitride were measured. The optimum mi-crostructure of silicon nitride with the excellent machinability was investigated by MFG(magnetic-fluid grinding) technique. An attempt was made to figure out how the mechanical properties influence upon the machinability of silicon nitride ball.

• The Korean Journal of Ceramics
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• v.6 no.4
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• pp.364-369
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• 2000

Silicon nitride with adding La$_2$O$_3$ was sintered by gas pressure sintering (GPS) technique at $1950^{\circ}C$, in $N_2$ gas at 3 MPa, for 2h. Mechanical properties such as hardness, flexural strength, and fracture toughness were determined as a function of the GPS holding time and the contents of La$_2$O$_3$ in silicon nitride. Also machinability of silicon nitride ball with various GPS holding time and amount of La$_2$O$_3$ was evaluated by magnetic fluid grinding (MFG) method. In this study it was found that machinability was influenced significantly with La$_2$O$_3$ contents. However, the different GPS holding time did not affect the machinability very much.