• 한국정밀공학회지
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• 제17권10호
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• pp.132-140
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• 2000

In conventional drilling, burr geometry can be changed according to the variation of drill geometry like point angle, rake angle. Step drilling is proposed to minimize the burr formation in drilling operation. The burr formed in first cutting can be removed in second cutting by the edge in step. The burr formed in second cutting by the edge in step can be minimized according to the change of geometry like, step angle and depth. The mechanism in step drilling is analyzed. Some step drills are applied to drilling the input shaft which is used for vehicle steering. To measure the burr formed in drilling, laser and height gage are used.

• 대한기계학회논문집
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• 제17권8호
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• pp.1910-1920
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• 1993

An experimental study to investigate the unconventional chip formation called triangulation of chip in cutting with a SPRT (self-propelled rotary tool) is performed using acoustic emission (AE) signal analysis. In doing that, a quantitative model of the AE RMS signal in triangulation with a SPRT is first developed. The predicted results from this model show good correlation between the AE RMS signal and the general characteristics of triangular chip formation. Then, effects of various process parameters such as cutting conditions (cutting speed, depth of cut, oblique angle and normal rake angle) and the work material properties on the chip formation in cutting with a SPRT are explored. Special attention is paid to the work material properties which are found to have significant effects on triangulation.

• 한국생산제조학회지
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• 제6권2호
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• pp.102-111
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• 1997

This paper deals with the machinability based on turning of WC-Co allows with the coated and the sintered diamond tools. The main conclusions obtained are as follows. (1) When machining WC-10%Co alloy, the flank wear of sintered diamond tool increases more largely with the increase of cutting speed in comparison with coated diamond tool. The tool wear decreases with the increase of the grain size and nose radius of sintered diamond tool. (2) When machining WC-20%Co alloy, the tool wear and cutting force decrease with the decrease of rake angle. Their exists a certain cutting speed range to exhibit the smallest tool wear in machining the WC-20%Co alloy, and this critical cutting speed becomes higher by 2 times in the case of coated diamond tool compared with sintered diamond tool. (3) The machinability becomes better with the increase of Co content. The effects of cutting speed and feed rate on the roughness of machined surface become smaller with the increase of Co content.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1991년도 추계학술대회 논문집
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• pp.54-58
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• 1991

It is well known that metal cutting leaves a plastically deformed layer in the machined surface. This residual phenomenon affects in various forms the physical properties of machined components such as the fatigue strength, the dimensional instability, microcracks, and the stress corrosion cracking. These physical properties, so called surface integrity, are very important for designing highly stressed and critically loaded components. Typical plastic strains in the machined surface are very difficult to measure, since they are located within a very short distance from the surface and they change very rapidly. There is an alternative way to determine the residual strain in plastically deformed materials by measuring the grain size after a subsequent recrystallization process. Although, this technique has been successfully applied by several researchers to find the plastic zone around notches and cracks in various materials and welding beads, few works have been reported using the recrystallization method to determine the residual strains in machined surface. Therefore, the purpose of this investigation Is to explore the effectiveness of the recrystallization technique in machining applications, and in particular, to find the effect of cutting parameters, i.e., depth of cut and rake angle on the plastic strains.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1998년도 학술발표대회 논문집 제17권 1호
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• pp.357-360
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• 1998

DS/CDMA system rejected narrow-band interference and additional White Gaussian noise which are occured at multipath, intentional jammer and multiuser to share same bandwidth in mobile communication systems. Because of having not sufficiently obtained processing gain which is related to system performance, they were not effectively suppressed. In this paper, an matched filter channel model using backpropagation neural network based on complex multilayer perceptron is presented for suppressing interference of narrow-band of direct sequence spread spectrum receiver in DS/CDMA mobile communication systems. Recursive least square backpropagation algorithm with backpropagation error is used for fast convergence and better performance in matched filter receiver scheme. According to signal noise ratio and transmission power ratio, computer simulation results show that bit error ratio of matched filter using backpropagation neural network improved than that of RAKE receiver of direct sequence spread spectrum considering of con-channel and narrow-band interference.

• 한국음향학회:학술대회논문집
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• 한국음향학회 2004년도 추계학술발표대회논문집 제23권 2호
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• pp.239-242
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• 2004

터보팬엔진등에서 발생하는 음장의 특징은 지배적인 음향모드 구조를 가진다는 점이다. 이러한 구조를 파악 해내는 것은 소음원을 찾아내고 그 소음원의 전파를 규명하여 소음을 저감하는데 중요한 기여를 할 수 있다. 음향모드의 검출을 위해서 많은 연구가 이루어져 왔으며 센서의 이용방식에 따라 원음장에서의 측정법, 회전형 갈퀴 (rotating rake)를 이용한 측정법, 덕트내 벽면에 센서를 분포시키는 측정법으로 나눌 수 있다. 이중 벽면에 센서를 위치시키는 방법은 다른 방법에 비해 빠르게 측정결과를 얻을 수 있으며 측정장치가 간단하다는 장점이 있다. 본 연구에서는 기존에 이 방법의 단점으로 여겨져 왔던 많은 수의 센서를 줄이는 새로운 센서 배치에 대해 기술하였으며 측정하고자 하는 주파수에 존재하는 전체 모드의 개수와 비교하여 최소한의 센서 개수를 설명하였다.

• 한국생산제조학회지
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• 제20권4호
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• pp.419-426
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• 2011

In this study, an experimental and theoretical program were carried out to determine the cutting forces and chip formation at different cutting speeds using a 0.4mm nose radius ceramic insert and -7 rake angle for non heat-treated AISI 4140 (27HRc) and heat-treated AISI 4140 (45 HRc) steel. The results obtained were compared to show the hardness differences between the materials. The secondary deformation zone thicknesses when comparing the two materials show different physical structure but similar size. These results were also discussed in light of the heat treatment and the effects it had on the machining characteristics of the material. In addition, the Oxley Machining Theory was used to predict the cutting forces for these materials and a comparison made. The predicted cutting performances were verified experimentally and showed good agreement with experimental data.

• International Journal of Precision Engineering and Manufacturing
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• 제1권1호
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• pp.15-21
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• 2000

This study presents a procedure for analyzing chip-tool friction and shear processes in 3-D cutting with a single point tool. The edge of a single point tool including a circular nose is modified to an equivalent straight edge, thereby reducing the 3-D cutting with a single point tool to the equivalent of oblique cutting. Then, by transforming the conventional coordinate systems and using the measurements of three cutting force components, the force components on the rake face and shear plane of the equivalent oblique cutting system can be obtained. As a result, the chip-tool friction and shear characteristics of 3-D cutting with a single point tool can be assessed.

• 한국정밀공학회지
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• 제14권3호
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• pp.122-129
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• 1997

Machining technology has emerged to the point of performing atomic-scale fabrication. In tail paper atomic-scale machining characteristics are investigated by using Molecular Statics simulation method. The cutting model used in this work simulates machining with tools such as an AFM. It is shown that built-up edge formation and cutting forces depend on tool tip geometry. Also, the material flow during cutting is shown for various cutting conditions such as depth of cut, rake angle, and edge radius of tool.

• International Journal of Automotive Technology
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• 제5권3호
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• pp.173-180
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• 2004

An intensive study was conducted for the crash worthy structural design of the recently developed Korean High Speed Train (KHST). Two main design concepts were set up to protect both crews and passengers from serious injury in heavy collision accidents, and to reduce damage to the train itself in light collision accidents. A collision against a movable 15-ton rigid obstacle at 110 kph was selected from train accident investigations as the accident scenario for the heavy collisions. A train-to-train collision at the relative velocity of 16 kph was used for the light collision. The crashworthiness behaviors of KHST were numerically evaluated using FEM. Analysis results using 1-D collision dynamics model of the full rake consist and 3-D shell element model of the front end structure showed good crashworthy responses in a viewpoint of structural design. Occupant analyses and sled tests demonstrated that KHST performed well enough to protect occupants under the considered accident scenarios. Finally our numerical approaches were evaluated by a real scale collision test.