• 한국철도학회:학술대회논문집
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• 한국철도학회 1998년도 추계학술대회 논문집
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• pp.595-600
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• 1998

Train wheels tend to wear abrasion due to frequent Starlings and brakings. They are important factors of train safety and noise. However, it is difficult and inaccurate to measure their shape and profile manually. Profile measurement system of train wheel with image processing is proposed. The system consists of CCD cameras, PCI image grabber board, and PC operated on Windows '95. Image processing algorithms such as filtering, histogram equalization, and edge detection are presented, and some processing results are illustrated.

• 대한치과보철학회지
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• 제37권1호
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• pp.51-70
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• 1999

Dental porcelain is one of the materials of choice for restoration where esthetics is of concern, but has a considerable potentials of wear. The wear of enamel is variable when opposed by different porcelain systems and surface conditions, and the exposed dentine and opaque porcelain due to clinical failure is expected to have high potentials of wear. The purpose of this study was to investigate the wear effects of self-glazed, polished incisal porcelain. polished dentine and opaque porcelain against human enamel in the laboratory by use of a pin-on-disk type wear tester. 4 types of dental porcelain($Vita-{\Omega}$, Ceramco-II, Vintage powder $Vita-{\alpha}$ of In-Ceram system) and type IV gold alloy as cotrol group were used for test specimens. Intact buccal cusps of maxillary premolar were used for enamel specimens, and the cusp converged to a point and was devoid of visible abrasion, caries, decalcification. The upper part was the cusp of a maxillary premolar and the lower part was a porcelain specimen. The enamel wear was deter-mined by weighing the cusp before and after each test. Surface profilometer was used to quantitate wear of the porcelain specimens. Vicker's hardness tester was used to evaluate the surface hardness of test specimens. The SEM was used to evaluate the wear surfaces. The results were as follows : 1 Self-glazed porcelain produced more enamel wear than polished porcelain, especially the enamel wear of $Vita-{\alpha}$ self-glazed porcelain was 3.2 times more than that of other groups. 2. Opaque porcelain produced least porcelain wear, $Vita-{\alpha}$ self-glazed porcelain produce greatest porcelain wear, but there was no statistically significant difference between the groups(p>0.05). 3. The enamel wear of dentine porcelain was 3.8 times more than that of polished inisal porcelain(p<0.05), and the enamel wear of opaque porcelain was 1.9 times more than that of polished inisal porcelain, but there was no statistically significant difference between the groups(p>0.05) 4. Overglazed porcelain produced less enamel wear than self-glazed porcelain, and more enamel wear than polished porcelain, but there was no statistically significant difference between the groups(P>0.05). 5. The hardness number of $Vita-{\Omega}$ dentine and Ceramco-II opaque porcelain was larger, but that of Vintage dentine and $Vita-{\alpha}$ self-glazed porcelain was similar to other groups. 6. Examination of SEM photographs revealed that overglazed porcelain had smoother surface than self-glazed porcelain, and self-glazed porcelain had smoother surface than polished porcelain. Much polishing scratches and larger porosities were observed on the opaque porcelain specimen, and much polishing scratchess and small porosities were observed on the dentine porcelain specimen.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1998년도 제27회 춘계학술대회
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• pp.91-96
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• 1998

In recent years, the tribological behavior of coated ceramic material has been the topic of much interest. Particularly, the understanding of the tribological performance of thin film under light load is important for potential applications in MEMS. In this work under light load and low speed, the tribological behavior of coated silicon was investigated. The results show that both adhesive and abrasive wear occur depending on the sliding condition. Also the effect of humidity on friction was influenced by the apparent ares of contact between the two surfaces. Finally, undulations on the silicon wafer were found to be effective in trapping wear particles.

• 반도체디스플레이기술학회지
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• 제6권2호
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• pp.25-28
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• 2007

Electroless Ni-P coating is widely used for chemical, electronic, and semiconductor equipment parts because of its corrosion resistance. The incorporation of chemically-inert PTFE particles into the Ni-P films improves properties such as, non-stick, anti-adhesive and better corrosion resistance. However, soft PTFE particles degrade the hardness, wear and abrasion resistance. In this study, effects of PTFE and W addition to the Ni-P-coatings were compared by the XRD, SEM, sheet resistance, contact angle, and microhardness measurements. The change in sheet resistance was negligible, but contact angle was doubled by the addition of PTFE and W. The microhardness was lower for Ni-P-PTFE, but higher for Ni-P-PTFE-W coatings, compared to that of Ni-P coatings.

• International Journal of Precision Engineering and Manufacturing
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• 제5권3호
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• pp.35-42
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• 2004

This research describes that the cutting characteristics and tool wear behavior in the micro cutting of three kinds of wear resistant cemented carbides (WC-Co; V40, V50 and V60) using PCD (Poly Crystalline Diamond) and PCBN (Poly crystalline Cubic Boron Nitride) cutting tools by use of the SEM (Scanning Electron Microscope) direct observation method. The purpose of this research is to present reasonable cutting conditions from the viewpoint of high efficient cutting refer to a precise finished surface and tool wear. Summary of the results is as follows: (1) The cutting forces tend to increase as the increase of the weight percentage of WC particles, and the thrust forces was larger than the principal forces in the cutting of WC-Co. These phenomena were different from the ordinary cutting such as cutting of steel or cast iron. (2) The cutting speed hardly influenced the thrust force, because of the frictional force between the cutting tool edge and small WC particles at low cutting speed region such as 2$\mu\textrm{m}$/s. It seemed that the thrust cutting force occurred by the contact between the flank face and work material near the cutting edge. (3) The wear mechanism for PCD tools is abrasion by hard WC particles of the work materials, which leads diamond grain to be detached from the bond. (4) From the SEM direct observation in cutting the WC-Co, it seems that WC particles are broken and come into contact with the tool edge directly. This causes tool wear, resulting in severe tool damage. (5) In the orthogonal micro cutting of WC-Co, the tool wear in the flank face was formed bigger than that in the rake face on orthogonal micro cutting. And the machining surface integrity on the side of the cutting tool with a negative rake angle was better than that with a positive one, as well as burr in the case of using the cutting tool with a negative rake angle was formed very little compared to the that with a positive one.

• 한국추진공학회지
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• 제17권5호
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• pp.113-120
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• 2013

마모 마찰기구로 널리 사용되는 그라파이트에 대하여, 고온가스 조절 밸브 내에서 가스 유입 방지용 씰링 그라파이트 소재(HK-6)의 고온 마모 거동에 대하여 연구하였다. 구동축과 라이너 사이에 위치하여 지속적인 마모의 발생을 모사하기 위해 왕복동 마모 시험을 수행하였다. 마모 거동 변화의 영향 인자로 접촉 하중, 미끄럼 속도, 온도를 설정하고 민감도를 확인하였다. 마모 발생이 가장 적고 씰링 그라파이트 소재(HK-6)의 효율이 증대되는 최적조건에 대해 논의하였다.

• 한국생산제조학회지
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• 제21권2호
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• pp.191-195
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• 2012

Heavy flint optical glass(SF57HHT) is new material that has extremely high transmittance. Due to brittleness and high hardness, optical glass is one of the most difficult to materials for ultra-precision turning. According to the hypothesis of ductile machining, all materials, regardless of their hardness and brittleness, will undergo transition from brittle to ductile machining region below critical undefromed chip thickness. In this study, cutting test was carried out to evaluate cutting performance of heavy flint glass using ultra-precision machine with single crystal diamond bite. The machined workpiece surface topography, tool wear and surface roughness were examined using AFM and SEM. The experimental results indicate that the machining mode become the brittle mode to ductile mode, when the maximum undeformed chip thinkness is large than critical value. Tool wear mainly occurs on the flank face and its wear mechanism is dominated by abrasion. This study demonstrates the feasibility of SF57HHT by diamond turning.

• Tribology and Lubricants
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• 제34권4호
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• pp.132-137
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• 2018

Ultrasonic waves are used in various applications in multiple devices, sensors, and high-power machinery, such as processing machines, welders, and cleaners, because the acoustic vibration frequencies are above the human audible frequency range. In ultrasonic machining, electrical energy at a high frequency of 20 kHz or more is converted into mechanical vibration by a vibrator and an amplifier. This technique allows instantaneous separation between a tool and a workpiece during machining, machining by pulse impulse force at the time of re-contact and minimizes the minute elastic deformations of the workpiece and machine tools due to the cutting effect. The Al7075 alloy used in this study is a typical aluminum alloy with superior strength that is mainly used in aircrafts, automobiles, and sporting goods. To investigate the optimal conditions for machining aluminum alloy using ultrasonic vibration, the present experiment utilized the Taguchi orthogonal array method, and the coefficient of friction was analyzed using the characteristics of the Taguchi technique. In ultrasonic friction and abrasion tests, the changes in the friction coefficient were measured in the absence of ultrasonic vibrations and at 28 kHz and 40 kHz. As a result, the most considerable influence on the friction coefficient was found to be the normal load, and the frequency of ultrasonic vibrations increases, the coefficient of friction increases. It was thus confirmed that the amount of wear increases when ultrasonic vibration is applied.

• Design & Manufacturing
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• 제8권2호
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• pp.37-40
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• 2014

A discharge electrode plays a role of shaving off workpiece with spark generated by current in discharge machining. Accordingly, for the discharge electrode, an electrode with excellent wear resistance is necessary. Generally, Graphite and Cu are used as the materials of the electrode, and recently Cu-W is mainly used as an electrode with excellent wear resistance. However, the form of the electrode generally used is produced mostly using cutting work, so a lot of costs incur if several similar forms are needed. Thus, this study developed a Cu-W electrode using Metal Injection Molding (MIM) process to produce similar forms with excellent productivity and a great quantity of electrodes in a similar form in discharge machining and carried out a discharge machining test. In developing an electrode applying MIM, predicting contraction of a product in a sintering process, a mold expansion ratio of 1.29486 was given, but the actual product showed a percentage of contraction 24% to 32%, which showed a difference of 3% to 5%. In addition, to verify wear resistance of the discharge electrode, abrasion loss was measured after the discharge.

• 한국주조공학회지
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• 제8권3호
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• pp.296-309
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• 1988

In this study the mechanical properties of ferritic ductile cast iron in as-cast are discussed by metallographic considering the effect of phosphorus content(about 0 - 0.8wt.%). In ferritic S.G. cast iron containing about 4.2wt.% Si, 0.5wt.% Ni, 0.02wt.%B, these samples are investigated for castability, microstructure, machinability, wear resistance, mechanical and thermal properties. The main results are summarized as follows. 1) The chill depth increased greatly with P addition up to about 0.6wt.% but the tensile strength and the elongation are decreased smoothly. 2) The size of S.G. and the amount of steadite increase with increasing P content. This means the tendency of increasing the number of S.G. 3) The maximum value of wear by mechanical fracture was appeared at the abrasion speed of 1.14m/sec and the plastic Flow layers are stretched longly on the wear surface with decreasing P content. 4) Although the coefficient of thermal expansion increased with P addition, the cast iron growth was slowing down extremely at 0.6w.% P or more.