• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.1
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• pp.69-76
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• 1997

This paper deals with the machinability based on turning and drilling tests. The main conclusions obtained were as follows. (1) Turning : The roughness of Machined surface decreases with the increase of the rake angle of tools, and the tool wear becomes smaller with the decrease of the rake angle. When the feed rate becomes larger, the fracture of work material in the vicinity of the cutting edge occurs on a larger scale, eventually decreasing tool wear. (2) Drilling : Considering both tool life and productivity, it is reasonable to cut with the high cutting speed and feed rate. The tool wear increases with the increase of feed rate, and the tendency of feed rate on tool wear becomes stronger at the cutting speed $\geq$30m/min.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.4
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• pp.119-126
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• 2007

Generally, the machinability of materials that have a good mechanical properties is poor. The material having a high strength, high toughness in high temperature and wear resistance, it is difficult to remove a chip from workpiece. STD11 and NAK80 are kinds of these materials and these materials can be used in many industrial fields. But it is limited in use because of high cost and poor machinability. In this experimental study, the cutting of STD11 and NAK80 were used to decide the machinability and the tool shape of CBN ball end mill. From the results, the CBN ball end mill is verified that the estimated cutting edge shape of rake angle 30 degree has consistent effect on the tool wear and cutting force.

• Journal of the Korean Society for Precision Engineering
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• v.6 no.4
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• pp.94-102
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• 1989

The effect of plastic strain on the surface integrity of mild steel (SS 41) was studied. This paper shows that the recrystallization technique is adequate to evaluate the plastic strain in a machined surface experimentally. The relations between the plastic strain and the machining conditions are quantitatively evaluated by using the recrystallization technique. The obtained results are summarized as follows. 1. The surface integrity of steel is considerably influenced by the amount of surface region deformation produced by changes in cutting conditions. 2. The plastic strain in machined surface produced by changes of the cutting conditions is evaluated by the recyrstallization technique. 3. The plastic strain increases with the increase of depth of cut and the decrease of rake angle. 4. When the cutting force is high and the rake angle is small, the value of maximum true strain reaches to high. 5. The maximum true strain is related to the cutting energy, and the values increase with the increase of the unit shear and total engergy in constant depth with the increase of the energy values.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.270-273
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• 2002

This paper presents an effective cutting force model that enable us to predict the instantaneous cutting force in milling process from a knowledge of the work material properties and cutting conditions. The development of the model is based on the orthogonal machining theory with the effective rake angle which is defined in the plane containing the cutting velocity and chip flow vectors. Face milling tests are performed at different feeds and, a fairly good agreement is shown between the predicted cutting forces and test results.

• Journal of electromagnetic engineering and science
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• v.4 no.4
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• pp.183-189
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• 2004

In this paper, the Eigen-RAKE receiver in wideband direct sequence code-division multiple access(DS-CDMA) systems with downlink smart antenna is analyzed for different spreading bandwidths(1.25 MHz, 5 MHz, 10 MHz) and different channel environments(macro, micro). The realistic spatio-temporal wideband multipath channel is assumed, one of which is standardized multiple-input single-output(MISO) radio channel model for WCDMA link-level simulations proposed by $3^{rd}$ generation partnership project(3GPP) contributions. We assumed spatial scattering phenomenon in which many unresolvable path signals within a limited range of spatial angle simultaneously contribute to the signals received at the receiver. Several multipaths within one chip are distinguished into each one and the first multipath components are selected as the desired signal and the others are considered self-interference. Downlink DS-CDMA system with eigenbeamformer using wider bandwidth present better performance than that using narrow bandwidth system by employing Eigen-RAKE receiver of many number of branches. It is shown that the downlink eigenbeamformer is more effective in typical urban macro cellular environments when using Eigen-RAKE receiver.

• Journal of the Korean Society for Marine Environment & Energy
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• v.14 no.4
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• pp.273-279
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• 2011

Turbulent flow analysis around a wind turbine blade was performed to evaluate the power performance of offshore wind turbine. Fluent package was utilized to solve the Reynolds-averaged Navier-Stokes equations in non-inertial rotating coordinates. The realizable k-$\varepsilon$ model was used for turbulence closure and the grid system combining structured and unstructured grids was generated. In the first, lift and drag forces of 2-D foil section were calculated and compared with existing experimental data for the validation. Then torque and thrust of the wind turbine blade having NACA 4-series sections were calculated with fixed pitch angle and rpm. Tip speed ratio was varied by changing wind speed. In the next, three kinds of end plate were attached at the tip of blade in order to increase the power of the wind turbine. Among them the end plate attached at the suction side of the blade was found to be most effective. Furthermore, performance analysis with tilt angle and rake was also performed.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.9
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• pp.55-62
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• 2003

This paper investigates the micro-cutting of cemented carbides using PCD (polycrystalline diamond) and PCBN (polycrystalline cubic boron nitride) cutting tools are performed with SEM direct observation method. The purpose of this study is to make clear the cutting mechanism of cemented carbides and the fracture of WC particles at the plastic deformation zone in orthogonal micro-cutting. And also to achieve systematic understanding, the effect of machining parameter on chip formation and machined surface was studied, including cutting speed, depth of cut and various tool rake angle. Summary of the results are shown below. (1) Three type of chip formation process have been proposed by the results of the direct observation in orthogonal micro-cutting of cemented carbide materials. (2) From the whole observation of chip formation, primary WC particles are crushed and/or fine grained in the shearing deformation zone. A part of them are observed to collide directly with a cutting edge of tool by following the micro-cutting. (3) Surface finish, surface morphology and surface integrity is good to obtain by cutting with PCD cutting tool compared with PCBN. (4) The machined surface has the best quality near the low cutting speed of 10${\mu}m$/sec with a cutting depth of 10 ${\mu}m$ using 0$^\circ$ rake angle and 3$^\circ$ flank angle in this condition, but it was found that excessively low speed, for example the extent of 1 ${\mu}m$/sec, is not good enough to select for various reason.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.2
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• pp.76-85
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• 1993

Based on the cutting force model, three-dimensional optimal design model was developed and optimal designed tool which is minimized cutting force is developed by computer simulation technique. In this model the objective function which is minimized resultant cutting force was used and the variables are radial rake angle, axial rake angle, lead angle of the tool. The cutting forces using conventional and optimal tools by simulation, are compared and analyzed in time and frequency domains. In time domain the cutting force of optimal tool in feed direction was more reduced and less fluctuated than that of conventional tool. Cutting forces of optimal tool in X-and Z-directions are shown a little increased than those of conventional tool. In frequency domain amplitude of insert frequency components of optimal tool in feed direction was more reduced than that of convent- ional tool. The amplitudes of insert frequency components of optimal tool in X-and Z-direction are a little increased than those of conventional tool. As the reduction of amplitude and fluctuations of the cutting force, Optimal tool is considered that tool life and surface roughness would be improved, and stable cutting would be expected.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.6
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• pp.1-9
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• 2002

This study describes the geometric characteristics and the 5-axis machining method in order to make end mill cutter coming with insert tips. End mill geometry is consisted of flute part and insert tip part. Flute part modeled by using ruled surfaces with constant helix angle, and insert tip part modeled by rectangular planes containing tapped hole of specified direction in its center. In this study, the modeled insert tip part considered both of a radial rake angle and a axial rake angle, because they were important cutting conditions. In order to machining the virtual end mill defined from geometric characteristics, we programmed a special software to machining the end mill considered in this study. This software can generate NC-codes about following processes, end milling or ball end milling of flute part end milling of rectangular plane, centering of hole, drilling of hole, and tapping of hole. Ant sampled end mills were modeled and machined on 5-axis CNC machining center with two index tables. Since machined end mills were very agreeable to designed end mills, we saw that the method proposed in this study can be very useful for manufacturing of end mill body with insert tip.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.259-260
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• 2013