• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1997.10a
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• pp.94-100
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• 1997

The purpose of this study is to investigate the effects of operation factors of a typical main spindle system on its efficiency. Among important factors, material type of ball-bearing, bearing-lubricant type and main spindle bearing preload are taken into considered.

• Korean Journal of Metals and Materials
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• v.48 no.6
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• pp.533-542
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• 2010

The specific motivation for joining an Al alloy and Zn-coated steel arises from the need to save fuel consumption by weight reduction and to enhance the durability of vehicle structures in the automobile industry. In this study, the lap joining A6K31 Al alloy (top) and SGARC340 Zn-coated steel (bottom) sheets with a thickness of 1.0 mm and 0.8 mm, respectively, was carried out using the friction stir weld (FSW) technique. The probe of a tool did not contact the surface of the lower Zn-coated steel sheet. The friction stir welding was carried out at rotation speeds of 1500 rpm and travel speeds of 80~200 mm/min. The effects of tool geometry and welding speed on the mechanical properties and the structure of a joint were investigated. The tensile properties for the joints welded with a larger tool were better than those for the joints done with a smaller tool. A good correlation between the tensile load and area of the welded region were observed. The bond strength using a larger tool (M4 and M3) decreased with an increase in welding speed. Most fractures occurred along the interface between the Zn-coated steel and the Al alloy. However, in certain conditions with a lower welding speed, fractures occurred at the A6K31 Al alloy.

• Transactions on Electrical and Electronic Materials
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• v.7 no.5
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• pp.235-239
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• 2006

Charge dynamics in polymeric materials after aged under ac electric field using the pulsed electroacoustic (PEA) technique is reported. The emphasis is placed on charge decay. The charge dynamics of the ac aged additive free low density polyethylene (LDPE) samples under dc bias differ from the sample without ac ageing, indicating changes brought in by ac ageing. It is believed that a slow decay rate of charge in the ac aged sample is related to the formation of deep traps in the material. However, chemical analysis by infrared spectroscope (FTIR) and Raman microscope reveals no significant chemical changes taken place in the bulk of the material after ac ageing. Further experiments on irradiated LDPE have revealed a similar behaviour, i.e. the charge decay is slower in irradiated samples than that of fresh sample. The findings presented clearly indicate that space charge measurement can be used as a diagnostic tool to monitor ageing in polymeric materials.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.2
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• pp.1-8
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• 2003

Conventionally used linear or circular interpolator is undesirable for the precision machining of 3D free-form surface as the following reason: the transmission errors due to the huge number of data, discontinuity of segmentation, unsmooth motion speed. To this regard, modern CNC machine tools are designed with the function of machining arbitrary parametric curves. However, these systems don't consider the adaptive federate, which dominates the quality of the machining process. This paper proposes a NURBS interpolator for the constant material removal rate. That is accomplished by the variable federate using curvature of curve. The curvature-compensated feederate system has important Potential applications in ensuring part accuracy and protecting cutting tool. The simulated result show it can be applicable to the real machining.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.988-992
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• 2002

Ultrasonic machining technology has been developed over recent years for the manufacture of and quality-assured precision parts for several industrial application such as optics, semiconductors, aerospace, and automobile application. The past decade has seen a tremendous in the use of ceramics in structural application. The excellent thermal, chemical and wear resistance of these material can be realized because of recent improvements in the overall strength and uniformity of advanced ceramics. Ultrasonic machining, in which abrasive particles in slurry with water are presented to the work surface in the presence of an ultrasonic-vibrating tool, is process which should be of considerable interest, as its potential is not limited by the electrical or chemical characteristics of the work material, making it suitable for application to ceramics. This paper intends to further the understanding of the basic mechanism of ultrasonic machining for brittle material and ultrasonic machining of ceramics based in the fracture-mechanic concept has been analyzed.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.2
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• pp.104-111
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• 2004

Ultrasonic machining is a non-thermal, non-chemical, md non-electorial material removal process, and thus results in minimum modifications in mechanical properties of the brittle material during the process. Also, ultrasonic machining is a non-contact process that utilize ultrasonic vibration to impact a brittle material. In this research characteristics of micro-hole machining for brittle materials by ultrasonic machining(USM) process have been investigated. And the effect of ultrasonic vibration on the machining conditions is analyzed when machining fir non-conductive brittle materials using tungsten carbide tools with a view to improve form and machining accuracy.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.2
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• pp.112-119
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• 2004

This paper discussed on the effect of an internal damping on the stability of an elastic material subjected to dry friction force. Dry friction forces act tangentially at the contact surface between a moving belt and elastic material. The elastic material on a belt moving is modeled for simplicity into a cantilevered beam subjected to distributed follower force. In the analysis, the discretized equations derived according to finite element method are used. The impulse response of the beam are studied by the mode superposition method to observe the growth rate of the motion. It is found that the internal damping in cantilevered beam subjected to distributed follower force may act destabilizing.

• Nuclear Engineering and Technology
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• v.45 no.5
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• pp.665-674
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• 2013

This paper presents the development and validation methods of the FUTURE (FUel cycle analysis Tool for nUcleaR Energy) code, which was developed for a dynamic material flow evaluation and economic analysis of the nuclear fuel cycle. This code enables an evaluation of a nuclear material flow and its economy for diverse nuclear fuel cycles based on a predictable scenario. The most notable virtue of this FUTURE code, which was developed using C# and MICROSOFT SQL DBMS, is that a program user can design a nuclear fuel cycle process easily using a standard process on the canvas screen through a drag-and-drop method. From the user's point of view, this code is very easy to use thanks to its high flexibility. In addition, the new code also enables the maintenance of data integrity by constructing a database environment of the results of the nuclear fuel cycle analyses.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.135-138
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• 2009

In this study we investigate the machining characteristics of tool material for cold forging by using the machining center. The test was in the SKD62 cold forging material by 2-edge endmill with cutting fluid. The coating conditions are depth of cut 1,2,3mm. WC-endmill, federate 20mm/min, cutting velocity 20m/min. The surface roughness increase as the depth of cut increase. Also cutting force increase whiles the depth of cut increase.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.861-862
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• 2006

The suitable tools for CGI material has not been developed yet because of high hardness, high toughness and very low machininability compared to the grey cast iron. And the tool life has been decreased as the contents of Ti in CGI material. From this research, we were able to do the high speed machining by using high toughness silicon nitride ceramic tools. The silicon nitride ceramic tool grade was specially designed and prepared with microstructure of elongated grains with higher aspect ratio (c/a) than conventional one.