• 한국정밀공학회지
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• 제31권9호
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• pp.783-790
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• 2014

Railway wheels and axles are the most critical parts of the railway rolling stock. The wheel carry axle loads and guide the vehicles on the track. Therefore, the contact surface of wheel are subjected to wear and fatigue process. The wheel damage can be divided into three types; wear, contact fatigue failure and thermal crack due to braking. Therefore, in the contact surface between the wheel and the rail, the materials are heat treated to have a specific hardness. The manufacturing quality of the wheel have a considerable influence on the formation of tread wear and damage. Also, the residual stress on wheel is formed during the manufacturing process is one of the main sources of the damage. In this paper, the mechanical characteristic and the residual stress according to wheel material have been evaluated by applying finite element analysis and conducting mechanical tests.

• 한국표면공학회지
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• 제44권6호
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• pp.277-283
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• 2011

In this study, the cavitation test and electrochemical experiments were conducted for ALBC3(Cu-Al) alloy that has an excellent corrosion resistance and cavitation characteristic in sea water. Based on the ASTMG32 regulation, the cavitation test was performed with the cavitation and cavitation erosion tester using piezoelectric effect. The electrochemical characteristics are evaluated with potentiostatic experiments in activation polarization potential range. As a result, cavitation damage is increased proportionally to temperature and time at $30{\mu}m$ amplitude. It is appeared that acceleration period in weight loss presented over 6 hours under the cavitation environment in sea water. In addition, corrosion damages were observed at the potential range of -3.2~-1.4 V as the result of potensiostatic experiments during 12 hours in activation polarization potential range.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.292-292
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• 2000

Since high-power CO$_2$ Laser can be make a high densed energy to Local processing area, manufacturing processes using the laser can be processed for very Localized areas at a very fast rate with minimal or no distortion. Accordingly, the laser has been widely used in the fields of thermal manufacturing processes such as welding, fusion cutting, grooving, and heat treatment of metals. In particular, interest in the laser heat treatment process has grown tremendously in the past few years. In this process, maintaining the uniform hardening depth is important problem to obtain good quality products and to reduce heat induced distortion and residual stress. For achieving this objective, we introduced a new design technique of a fuzzy logic controller that greatly simplified the design procedure by defining several simplified design parameters. In the design procedure, the major design parameters of the controller are characterized by identifying several common aspects. From a series of simulation results, we found that the proposed design technique can be effectively used to design of a fuzzy logic controller for the LASER surface hardening process.

• 동력기계공학회지
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• 제9권1호
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• pp.76-81
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• 2005

The effect of micro-pulse plasma nitriding temperature and time on the case thickness, hardness and nitride formation in the surface of Fe-12Cr-22Mn-X alloy with 3% Co and 1% Ti alloys elements investigated. External compound layer and internal diffusion layer was constituted in plasma nitride case of Fe-12Cr-22Mn-X alloys and formed nitride phase such as ${\gamma}'-Fe4N\;and\;{\varepsilon}-Fe2-3N$. Case depth increased with increasing the plasma nitriding temperature and time. Surface hardness of nitrided Fe-12Cr-22Mn-X alloys obtained the above value of Hv 1,600 and case depth obtained the above value of $45{\mu}m$ in Fe-12Cr-22Mn-3Co alloy and $60{\mu}m$ in Fe-12Cr-22Mn-1Ti alloy. Wear-resistance increased with increasing plasma nitriding time and showing the higher value in Fe-12Cr-22Mn-1Ti alloy than Fe-12Cr-22Mn-3Co alloy.

• 열처리공학회지
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• 제19권3호
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• pp.163-169
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• 2006

Fretting is a kind of surface degradation mechanism observed in mechanical components and structures. The fretting damage decreases into 50-70% of the plain fatigue strength. The connecting rod for automobile has been used in special environments and various loading conditions. Failure of connecting rod in automotive engine may cause catastrophic situation. In this study, we investigated the fatigue characteristic of connecting rod material for an automobile. Fatigue life is defined as the number of cyclic stress to failure by regular cyclic stress. Fatigue life of C70S6 specimen was obtained from 134,000 to 147,000 cycles. Fatigue limit showed 432MPa by normal fatigue test. The other hands, it was 96MPa in the case of fretting fatigue test. It was extremely lower than that of a normal fatigue test. From observation of fracture surface, it was confirmed that the fatigue crack was initiated at the boundary of a specimen and bridge pad.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.136-136
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• 2016

Commonly used oil-based polymer resin has environmental and safety issues. Many researches for replacing the harmful solvent-borne resins to water-borne resins have been investigated to purify harmful environmental resources and follow the export and import of hazardous materials regulations. In this research, ultrasonic spray coatings of aqueous polymer resin were studied to fabricate thin insulating layer (${\sim}{\mu}m$) on the rectangular copper wire. It needs to have appropriate wettability between resin and substrate during the ultrasonic spray coating process to coat aqueous polymer uniformly. Furthermore, stabilities of coating solution and fabricating process are required to form thin insulating layer on the substrate. In here, physical characteristics such as viscosity of 6 types of commercial polymer dispersions and emersions were analyzed to confirm compatibility for ultrasonic spray coating process. These resins were dissolved in isopropyl alcohol, used for true solvent, and were diluted with ethanol, utilized for diluent. Also, solubilities, dispersion characteristics, and viscosities of these diluted polymer resin solutions were confirmed. Dispersion characteristic and viscosity of coating solution affects jetting of ultrasonic spray coating and these jetting characteristics influence morphologies of insulating layer. In conclusion, we have known that aqueous polymer solution should have outstanding dispersion characteristic and certain range of viscosity to fabricate thin polymer insulating layer uniformly with ultrasonic spray coating.

• 산업공학
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• 제9권1호
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• pp.13-24
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• 1996

Quality of injection molded parts is dependent on both mold design and processing conditions. From the mold design point of view, an optimal shrinkage should be used to compensate the shrinkage of molded parts. From the processing point of view, it is important to analyze the priority of processing conditions because a number processing conditions affect the quality of molded parts. Processing analysis employing the design of experiment was performed, and the shrinkage of molded part was considered as a characteristic parameter to improve the quality. As the result of the analysis of variance on SN ratio of a characteristic value, injection speed and bolding pressure were selected as two effective process parameters. Regression analysis on shrinkage and processing conditions was carried out, and an optimal processing condition was obtained by the response surface analysis. Shrinkage at the optimal condition could be used to reduce the number of try-cut at the step of mold making. The ranges of indirect control parameter, such as maximum cavity pressure or weight, measured at the optimal processing condition were used for monitoring the quality of molded parts in process.

• 한국추진공학회지
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• 제11권5호
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• pp.14-22
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• 2007

측면 표면 기울기가 변화하는 역 사다리꼴 핀이 2차원 해석적 방법을 사용하여 최적화된다. 핀 바닥 경계조건을 위해서, 내부유체로부터 내벽까지의 대류와 내벽부터 핀 바닥까지의 전도가 고려된다. 핀 끝 면으로부터의 열손실은 무시되지 않는다. 실제적인 핀 길이에서의 최대 열손실, 그 최대 열손실이 발생할 때의 최적의 효율, 핀 길이 그리고 핀 바닥 높이가 핀 내 외부의 대류특성계수의 함수로 나타내어진다. 결과 중 하나는 핀 바닥 높이에 대한 핀 끝 높이의 비가 커질수록 최적의 핀 형상은 두껍고 짧아지는 형상이 됨을 보여준다.

• 한국산학기술학회논문지
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• 제10권3호
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• pp.521-528
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• 2009

본 연구는 일체형 곡물 건조/저장 시스템에 채용되고 있는 Straight Type Sweeping Auger에 대한 성능과 적합성 검사를 실험을 통하여 검증하였다. 일체형 곡물 건조/저장 시스템의 핵심 기술은 선입선출을 가능토록 하는 Sweeping Auger의 설계기술에 있다. 바람직한 Sweeping Auger의 설계방향을 제시하기 위하여 Straight Type Sweeping Auger가 곡물 속에서 회전할 때 원주면에서 유동하는 곡물의 거동을 알아보기 위한 실험을 실시하고 결과 분석을 통하여 원인규명을 하였다.

• 마이크로전자및패키징학회지
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• 제19권2호
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• pp.67-72
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• 2012

최근에 전자 산업 분야에서 장치의 고용량을 구현 하기 위해 구동 drive IC의 선폭은 좁아지고 집적도는 증가하고 있다. 이러한 반도체, 전자 산업 분야의 초소형화, 고밀도화에 따라 FCCL(Flexible Copper Clad Laminate)의 표면 품질이 더욱 중요해 지고 있다. FCCL의 표면 결함으로는 돌기, 스크레치, 덴트 등이 있다. 특히 돌기가 표면에 존재할 경우 후속 공정에서 쇼트와 같은 불량을 유발할 수 있으며, 제품의 품질 저하를 야기 시킬 수 있다. 하지만 표면에 돌기가 존재한다 하더라도, 전해액의 레벨링 특성이 우수하다면 돌기의 성장을 막을 수 있다.평탄하고, 결함이 없는 도금표면을 얻기 위해서는 첨가제의 역할이 필수적이다. 평탄한 구리 표면을 형성하기 위해서 stock solution에 가속제, 억제제, 레벨러를 첨가하였다. 레벨러를 첨가하는 이유는 평탄한 표면을 얻고, 돌기의 형성을 억제하기 위함이다. 구리도금 표면 형상을 향상시키기 위한 레벨러로는 SO(Safranin O), MV(Methylene Violet), AB(Alcian Blue), JGB(Janus Green B), DB(Diazine Black) and PVP(Polyvinyl Pyrrolidone)가 사용되었다. 도금 첨가제와 도금 조건의 변화를 통해 도금시레벨링 특성을 향상시키고, 레벨링 특성 측정을 위해 니켈 인공돌기를 제작 한 후 레벨링 특성을 측정하였다.