• Journal of the Korean Society for Precision Engineering
• /
• v.15 no.11
• /
• pp.32-38
• /
• 1998

For the purpose of monitoring the abnormal state in proportion to cutting in automatic production process, the 3 kinds of specimens different from mechanical properties by austempering through temperature variation were manufactured, and the effects of tool wear on thrust and AE RMS was analyzed with sequential drilling in in-process. When the ADI specimens were drilled, the relationship of thrust and AE RMS with flank wear was studied through experiments, and it is confirmed that the reliable wear state is able to be monitored by using these signals. It was shown that thrust and AE RMS increased slowly till flank wear reached to V$_{B}$ = 0.25mm, and they increased steeply over the value. The effective tool exchange time was able to be pre-estimated by using this fact. It was validated that the tool breakage was able to be detected on the real time by monitoring in in-process.s.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 1996.10a
• /
• pp.163-167
• /
• 1996

The life of rolling elements depends on various factors such as operating conditions and material properties. In this work, the effect of microstructure on the rolling behavior is investigated. Specially, the deformations in the substrate regions before and after rolling are compared. It is found that rolling action causes severe flow of material in the direction opposite to the rolling direction in the case of dry rolling direction. With lubrication, the deformation is more severe at the subsurface region rather than at the surface.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.11 no.5
• /
• pp.88-92
• /
• 2002

This research is about slurry wear of SM45C and SUS304, which using standard sand and KUM river sand. The results are as follows ; 1. Mass loss rates of both standard sand and KUM river sand were linearly increased as increasement of time and velocity. 2. The average diameter of sand from relatively, less wear rate and portion of larger particles. 3. Wear resistance was linear with time and velocity of liquid jet regardless of type of sand. Also, it was able to evaluate with the formula, $HV^2$/E calibrated with n, the velocity index. 4. The wear surface in liquid jet experiment was smooth. The maximum wear depth was observed at the location 2~4mm apart from the center in the condition of $90^{\circ}$ of collision angle 6mm of nozzle diameter, and 20mm of collision distance. The sectional shape in radial appeared as 'W'shape.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2001.04a
• /
• pp.798-801
• /
• 2001

This research is about slurry wear of SM45C and SUS304, which using standard sand and KUM river sand. The results are as follows ; 1. Mass loss rates of both standard sand and KUM river sand were linearly increased as increasement of time and velocity. 2. The average diameter of sand from relatively, less wear rate and portion of larger particles. 3. Wear resistance was linear with time and velocity of liquid jet regardless of type of sand. Also it was able to evaluate with the formula, HV2/E calibrated with n, the velocity index. 4. The wear surface in liquid jet experiment was smooth. The maximum wear depth was observed at the location, 2~4mm apart from the center in the condition of 90$^{\circ}$of collision angle 6mm of nozzle diameter, and 20mm of collision distance. The sectional shape in radial appeared as 'W' shape.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1999.10a
• /
• pp.332-338
• /
• 1999

Surface hardening of plain carbon steel (SM$%C) by Laser are usually much finer and stronger than those of the base metals. The present study was undertaken to investigate the wear resistance and a processing parameters such as, power density, pulse width, defocusing distance, and molten depth for surface modification of plain carbon steel. The wear test was carried out under experimental condition using the wear test device, and in which the annular surfaces of wear test specimens as well as mating specimen of alumina ceramics(Al2O3) was rubbed in dry sliding condition. It is shown that molten depth and width depend on defocusing distance. The wear loss on variation of sliding speed was much in lower speed range below 0.2m/sec and in higher speed range above 0.7m/sec, but wear loss was little in intermediate speed range. It depends on oxidation speed and wear speed.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.4 no.4
• /
• pp.61-68
• /
• 1995

TiC-Al2O3 composite ceramics has high hardness, high strength, high wear and corrosion resistance. Therefore, composite ceramics have been concerned significantly with some excellent properties and many functions as new industrial materials to the industry at large. In present research, experiments are carried out to obtain the machinability and machining properties by EDM. As a result, the most suitable machining conditions of TiC-Al2O3 composite ceramics was that the pulse duration is 10-60$mutextrm{s}$, the peak current is 10-16A. The machining speed and the wear of the tool electrode increased with the increase in peak current.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.8 no.3
• /
• pp.257-263
• /
• 1984

저항 점 용접시 발생하는 어려운 문제점의 하나는 아무리 동일한 용접조건 하에서 용접을 한다하 더라도 균일한 용접품질을 얻을 수 없다는 점이다. 이는 주로 용접중의 전원에서의 변화로 인한 용접전류 및 전압변동, 용접모재의 표면상태 및 두께의 불균일, 두 전극의 마멸 및 맞춤상태 등의 인자 때문에 기인한다고 볼 수 있다. 이러한 문제점을 해결하기 위해서는 용접하는 도중에 수시 로 인자 때문에 기인한다고 볼 수 있다. 이러한 문제점을 해결하기 위해서는 용접하는 도중에 수 시로 용접 상태를 점검하여 용접조건을 그때 그때에 적합하게 변화시켜 주는 것이 바람직한데 우 선 용접상태를 판별하기 위해서는 용접품질(weld quality)을 잘 대변할 수 있는 용접법 변수를 찾 아내는 것이 중요한 일이다. 따라서 본 논문에서는 용접품질에 관련되는 변수중, 전기동저항과 전 극분리현상을 측정해서 마이크로 컴퓨터를 사용하여 관련되는 특정값들을 구했고 이들과 인장실 험에서 얻은 용접강도와의 상관관계를 얻음으로써 과연 어떠한 공정변수가 용접품질을 잘 대변해 줄 수 있는가를 실험적으로 조사하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2001.10a
• /
• pp.159-163
• /
• 2001

마찰구동은 다른 구동방식에 비하여 구조가 간단하고, 기계적인 정도를 얻기 쉬우며, 백래쉬 등에 기인하는 비선형 요소인 로스트모션이 없고 관성이 작아 구동력이 작은 이점이 있다. 그 반면에 접촉부에서 미끄럼이 발생하여 큰 구동력을 얻기 어렵고 마찰저항에 의하여 마멸이 생기는 결점이 지적되고 있다. 본 연구에서는 초정밀가공기용 위치결정기구로 마찰구동기구를 사용하기 위하여 위치 결정도에 관한 설계, 구동력의 설계 및 재료의 선택에 관하 여 분석하고 시작품을 제작하여 특성을 연구하였다.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 1995.06a
• /
• pp.25-30
• /
• 1995

본 연구에서는 건식 구름접촉시 발생하는 tribological한 현상들을 plate on ball tester를 이용하여 실험적으로 고찰하였다. 실험의 주된 관심은 각 열처리 방법으로 제작한 시편에 대하여 건식 구름접촉시 cycle수에 따른 plate의 표면 거칠기, 트랙의 형상, 졍도 및 구름저항의 변화이며 이런 자료를 토대로 열처리공정의 차이에서 오는 정도수명 및 피로수명에 대한 상대평가를 통해 마찰, 마멸의 저감에 적합한 열처리방법을 제시하고자 한다.

• Journal of the Korean Electrochemical Society
• /
• v.3 no.4
• /
• pp.211-218
• /
• 2000

The effects of alloying elements, Cr, Mo, and N on repassivation characteristics of stainless steels were investigated by using the abrading electrode technique and a.c impedance spectroscopy. The role of alloying elements on the stability of passive film and their repassivation characteristics were examined using alloy steels such as Fe-Cr, Fe-Cr-Mo, 304, 304LN, 316, and 316LN. The electrochemical characteristics of the passive film were investigated by in-situ d.c. and a.c. electrochemical methods. Localized corrosion resistance is believed to have much to do with the stability and repassivation characteristics of the passive film. The effects of alloying elements on the current transients and repassivation kinetics were systematically examined by using the abrading electrode technique and a.c. impedance spectroscopy. The experimental results were analyzed in order to elucidate the relationship between passive film stability, repassivation characteristics, and alloying elements.