• 한국세라믹학회지
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• 제27권3호
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• pp.369-382
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• 1990

ZrO2-Toughened Alumina-Ceramics(ZTA) with Cr2O3 and HfO2 as addition were synthesized by assintering method for solid solution of Al2O3/Cr2O3 and ZrO2/HfO2, and were prepared by pressureless sintering at 1$600^{\circ}C$. The effects of Cr2O3 and HfO2 on the thermal and mechanical properties, the sintering mechanism, and the wearness between theory and experiment were investigated. Among three kinds of mechanisms such as stress-induced transformation, microcracking, and crack deflection it contributed to the ZTA system with a few exceptons according to composite. We show that wearness can be estimated sufficiently by HV and KIC through theory and experiment.

• 대한소아치과학회지
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• 제28권4호
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• pp.654-660
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• 2001

상아질형성부전증은 유전적인 상아질의 결함으로 치아 발육과정 중 조직분화기에 발생되며 유치와 영구치 모두에서 나타난다. Shields등은 상아질형성부전증을 type I, II, III로 분류하였으며, Witkop에 따르면 1/8000명의 빈도로 이러한 유전적 소인을 갖게 되며, 남녀간의 차이는 뚜렷하지 않다고 한다. 이환받은 치아는 적갈색의 변색과 함께 심한 마모현상으로 인해 구치부 교합면과 전치의 절단면의 법랑질이 파괴되고 그후 급속도로 상아질의 파괴가 뒤따른다. 방사선학적으로 가느다란 치근과 구근상치관, 치경부 협착, 작거나 결손된 치수강이 관찰되고, 유치열에서 치근단병소나 다발성 치근파절이 관찰되기도 한다. 본 증례의 4세 남자환아는 치아색이 이상하다는 것을 주소로 연세대학교 치과병원 소아치과에 내원하였다. 치아는 전반적으로 황갈색의 변색과 중등도의 마모도를 보였으며, 방사선 검사 소견에서 치아의 치수강 폐쇄, 구근상치관, 짧은 치근들이 관찰되었다. 가족력상 각 세대마다 환아와 같은 치아변색과 마모의 유전양상이 관찰되었으며, 10세된 환아의누나는 영구치열에 전체적으로 회갈색의 변색과 경도의 마모도를 보였다. 임상 및, 방사선학적 검사소견상 상아질형성부전증으로 판단되어 환아의 손상된 치아에 대해 구치부는 기성금관 수복을, open-faced stainless steel crown으로 치근파절로 인해 발거된 상악 좌측 유중절치를 포함한 손상된 전치부를 수복해 기능적, 심미적으로 만족할 만한 결과를 얻어 이에 보고를 하는 바이다.

• Journal of Periodontal and Implant Science
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• 제21권1호
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• pp.178-178
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• 1991

• Journal of Biosystems Engineering
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• 제18권1호
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• pp.15-20
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• 1993

Wearness has been a major failure criterion in Korean-made rotary blade. However, few studies have been conducted to improve it. In this study, the fundamental data obtained from the measurement of wearness and failure of rotary blade were analyzed to provide a guideline for the design of rotary blades. For the straight part(about 20-23 em from bolt hole) from the bolt hole to bending point of rotary blade, modifications were proposed for improvements, however, for the portion from bending point to tip was made no design recommendations because the failure behavior of that portion was difficult to analyze with the experimental data. The results are summarized as follows. 1. The current V-shape section has to be moved about 5 em toward the bending point of rotary blade. 2. The section modulus at the portion about 5-7 em distant from bolt hole has to be increased about 15-20 %. 3. The V-shape section has to be changed into U-shape to reduce the on account of recieving initial stress in blades. 4. The radius of curvature of the neck(the portion about 5-7 cm apart from bolt hole) has to be made larger to decrease the stress concentration.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2001년도 추계학술대회 학술발표 논문집
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• pp.74-77
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• 2001

One of the most important technology in PA(Factory Automation) is to construct the diagnostic system for manufacturing process. To improve the productibility in the factory, the state of tools such as bite, drill, endmill should be monitored continuously. In this study, fuzzy logic was used to check the wear of drill in drilling process. The input variables to construct the fuzzy rules are cutting force and the rate of cutting force's change. The experiment was done with the fixed spindle speed and feed rate in cutting condition.

• 한국공작기계학회논문집
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• 제14권5호
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• pp.21-26
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• 2005

It is important to measure the rotational accuracy of NC lathe spindle as it affects to the qualities of all machines machined by the NC lathe using in industries. The bad rotational accuracy of NC lathe spindle are caused mainly by wearness of the spindle in using and quality of spindle when machining and using low level bearings. It occurs especially in case of NC lathes because the cutting force acting to work-piece act on one side to the spindle not to both sides symmetrically. Therefore in this study, constructing experimental appratus for measuring of rotational accuracy by using eddy current type gap sensors, converters, screw terminal, data acquisition board inserted in computer and software f3r data acquisition, DT VEE ver. 5.0 and then error data acquired in the rotational accuracy test of NC lathe spindle are analysed in plots and statistical treatments.

• 한국공작기계학회논문집
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• 제16권6호
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• pp.43-48
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• 2007

It is important to measure the rotational accuracy of lathe spindle as it affects to the qualities of all machines machined by the lathe using in industries. The bad rotational accuracy of lathe spindle are caused mainly by wearness of the spindle in using and quality of spindle when machining and using low level bearings. It occurs especially in case of lathes because the cutting force acting to work-piece act on one side to the spindle not to both sides symmetrically. Therefore in this study, constructing experimental apparatus for measuring of rotational accuracy by using eddy current type gap sensors AEC5706PS and sensors, s-06LN, data acquisition board DT9834(USB type) and software for data acquisition, DT Measure Foundry ver. 4.0.7 etc., error data acquired in the rotational accuracy test of lathe spindle are analysed in plots and statistical treatments.

• Journal of Welding and Joining
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• 제11권2호
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• pp.74-85
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• 1993

Effect of Si metal powders addition with the plasma transferred arc(PTA) overlaying process on characteristics of the alloyed layer in aluminum alloy(A5083) has been investigated. The overlaying conditions were 175-250A in plasma arc current, 500mm/min in travel speed, the 5-20g/min in powder feeding rate. Main results obtained are summarized as follows. 1)Sufficient size of molten pool on surface of base metal was required for forming an alloyed layer; in a fixed travel, the formation of alloyed layer with clear and beautiful surface depend upon the plasma arc current and powder feeding rate; the greater plasma arc current and the smaller powder feeding rate were, the better bead was formed. Optimum alloyed conditions by which an excellent alloyed bead obtained was 225A in plasma arc current. PTA process made it possible to form an alloyed layer with up to 67wt% Si. 2)Microstructure in the alloyed layer was in accord with prediction from the Al-Si phase diagram 3)The hardness of the alloyed layer increased in proportion to Si content. 4)As volume fraction of primary Si increased, the specific wearness of the alloyed layer was significantly improved. However, no further improvement was found when the volume fraction was greater than about 30%. 5)Utilizing the PTA process, a crack free alloyed layer with maximum hardness of about Hv 310 could be obtained.