• Tribology and Lubricants
• /
• 제30권2호
• /
• pp.99-107
• /
• 2014

Fretting corrosion tests are conducted with a constant displacement amplitude using silver-plated brass coupons to investigate the effect of contact pressure on fretting corrosion. Three behaviors are identified based on the change in electric resistance and friction coefficient during the fretting test period, and the identified behaviors are dependent on the magnitude of the applied load. The failure cycle ($N_f$) with an electric resistance of 0.1 D cannot be achieved due to the adhesion behavior of the metal and metal contact under the higher applied load of 0.45 N. This suggests that an average contact pressure higher than 159 MPa for the silver-coated connector is desirable to gain an almost infinite lifetime. The relationship between the electric contact resistance (R) and the average contact pressure (p) can be written as $p=106.2{\times}{\Omega}^{-1.5}$.

• 한국정밀공학회지
• /
• 제13권12호
• /
• pp.151-157
• /
• 1996

The tool condition monitoring is one of the most important aspects to improve productivity and quality of workpiece. In this study, the wear of ceramic tool (A1$_{2}$0$_{3}$-TiC Series) cutting the hardened die material(SKD11) was investigated. Flank wear was more dominant than crater wear. Therefore the modeling of cutting force related to flank wear has been performed. The cutting force model was construct- ed by an assumption that the stress distribution on the tool face is affected by tool wear. The relationship between characteristics as cutting force and tool wear can be suggested by machining parameters depending on cutting conditions. Experiments were performed under the various cutting conditions to ensure the validity of force models. The theoretical predictions on the flank wear are approximately in good agreement with experimental results.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1993년도 추계학술대회 논문집
• /
• pp.155-160
• /
• 1993

연삭가공은 숫돌의 입자가 마멸,파쇄,탈락,생성의 과정을 반복하면서 가공하는 것으로 연삭과정은 사용하는 연삭숫돌의 종류, 드레싱조건,연삭조건 등의 인자에 영행을 받는다. 더욱이 연삭숫돌의 연삭성능은 연삭가공시간의 경과에 따라 변화한다. 이때 요구되는 가공능률과 가공정밀도를 일정하게 유지하기 위해서는 연삭과정을 자동감시하고 이상상태를 진단하는 기술의 확립이 필수적이다. 본 연구에서는 AE를 이용하여 평면연삭에 있어서 연삭숫돌의 종류별(WA계 비트리파이드 및 레지노이드결하ㅂ제연삭숫돌 36종류) 및 연삭조건을 변화시켰을때의 연삭저항 및 AE 신호의 변화등을 In-process 검출하여 연삭가공상태의 자동감시 및 자동이상진단시스템을 위한 AE의 적용 가능성을 검토하였다.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1993년도 추계학술대회 논문집
• /
• pp.126-130
• /
• 1993

소경드릴가공은 많은 기계가가공중에서도 가장 곤란한 가공의 하나이다.그것은 가공구멍단면 이하의 공간속에서 공구강성이나 칩처리들이 고려되어야 한다는 엄격한 제한이 소경이란 형태에서 한층 어려워지기 때문이다.소경의 구멍가공은 최근 전자제품,우주항공기 부품,소형정밀부품, 섬유산업의 광섬유관련품 등에 까지 수요가 증가함에 따라 레이져가공,전자빔가공,전해가공과 같은 전기물리적가공법이 많이 사용되고 있지만 생산성 및 가공정밀도의 관점에서 만족스러운 결과를 얻을 수 없는 실정이다, 이에반해 기계가공인 소경드릴가공은 공구강성저하로 인해 쉽게 파손된다는 점은 있지만 가공정도가 양호하고 종횡비가 높은 가공이 가능하여 실용화가 가장 좋은 분야라고 할수 있다. 이로 인해 최근에는 여기에 관한 많은 연구가 지행되고 있다. 또한 기계가공의 자동화가 진전됨에 따라서 단일공국의 대표적 공구인 바이트의 결함을 검출하는것 못지않게 드릴의 마멸이나 절손의 검출 또는 예측이 중요한 문제로 부각됨에 따라 절삭저항의 이용이 증가할 것으로 생각된다. 따라서 본 연구에서는 ADI에 포함된 Si량이 드릴가공시 ADI의 피삭성에 미치는 영향을 절삭조건을 변화시켜 고찰함과 동시에 공구수명에 대하여 고찰하였다.

• 한국기계가공학회지
• /
• 제7권4호
• /
• pp.3-9
• /
• 2008

The ion implantation technology is generally used in order to improve surface mechanical properties, especially tribological properties, of engineering metals. In this study, experimental works were carried out to investigate the surface properties, such as hardness, wear quantity, wear rate and friction force, of a nitrogen ion implanted tool steel STD11 under dry condition. Specimens for the wear test were made to investigate the influences of the initial ion implantation temperature and the total ion radiation. Wear properties, such as the wear quantity and the wear rate, of the nitrogen ion implanted tool steel were considerably improved, especially under the low sliding speed and the low applied load.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 1999년도 추계학술대회 논문집 - 한국공작기계학회
• /
• 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.

• 한국기계가공학회지
• /
• 제16권4호
• /
• pp.104-112
• /
• 2017

In the sand casting process, the flow of liquid metal affects the quality of casting products and their die life. To determine the optimal bush part design process, this study performed various analyses using commercial finite element analysis S/W. The simulation focused on the molten metal behaviors during the mold filling and solidification stages of sand casting. This study aims to develop methods to reduce the cost and increase the tool life of the continuous hot zinc plating roll.

• 한국생산제조학회지
• /
• 제4권4호
• /
• 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.

• 한국정밀공학회지
• /
• 제20권10호
• /
• pp.74-81
• /
• 2003

This paper describes that the micro-cutting of WC-Co using PCD (Polycrystalline Diamond) and PcBN (Polycrystalline Cubic Boron Nitride) cutting tools are performed with SEM(Scanning Electron Microscope) direct observation method. The purpose of this study is to present reasonable cutting conditions to obtain precise finished surface and machining efficiency. Summary of the results are shown below: (1) The thrust cutting forces tend to increase more than the principal forces as the depth of cut and the cuttlllg speed are increased preferably on orthogonal microcutting. (2) The tool wear in the flank face was formed larger than that in the rake face on orthogonal micro cutting. (3) The wear appearance for PCD tools is abraded by hard WC particles of the work materials, which lead diamond grain to be detached from the bond.

• 한국생산제조학회지
• /
• 제22권1호
• /
• pp.85-91
• /
• 2013

The machinability of wear-resistible tungsten carbides and the tool wear behavior in machining of V30 and V50 tungsten carbides using PCD (Poly Crystalline Diamond) cutting tool was investigated to understand machining characteristics. This material is one of the difficult-to-cut materials in present, but their usage has been already broadened to every commercial applications such as mining tools, and impact resistant tools etc. Summary of the results are as follows. (1) Tool wear progression of PCD tools in turning of wear-resistible tungsten carbides were observed specially fast in primary cutting distance within 10m. (2) Three components of cutting resistance in this research were different in balance from the ordinary cutting such as that cutting of steel or cast iron. Those were expressed large value by order of thrust force, principal force, feed force. (3) If presume from viewpoint of high efficient cutting within this research, a proper cutting speed was 15m/min and a proper feed rate was 0.1mm/rev. In this case, it was found that the tool life of PCD tool was cutting distance until 230m approximately. (4) In cutting of wear-resistible tungsten carbides such as V30 and V50, it was recognized that the tool wear rate of V30 was very fast as compared with V50. (5) When the depth of cut was 0.1mm, there was no influence of the feed rate on the feed force. And the feed force tended to decrease as the cutting distance was long, because the tool was worn and the tool edge retreated. (6) It was observed that the tungsten carbides were adhered to the flank.