• Title, Summary, Keyword: 마멸손실

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Tribology of Si3N4 Ceramics Depending on Amount of Added SiO2 Nanocolloid (SiO2 나노 콜로이드 첨가량에 따른 질화규소의 트라이볼러지)

  • Nam, Ki-Woo;Chung, Young-Kyu;Hwang, Seok-Hwan;Kim, Jong-Soon;Moon, Chang-Kwon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.3
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    • pp.267-272
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    • 2011
  • We analyzed the wear characterization of $Si_3N_4$ ceramics according to the amount of added $SiO_2$ nanocolloid. The test specimen was prepared by hot-press sintering at 35 MPa and 2123 K in an $N_2$ gas atmosphere for 1 h. A wear test was performed with a block-on-ring tester, and the test conditions were as follows: (1) the ring with a diameter of 35 mm had a rotational speed of 50 rpm; (2) the load was 9.8 N; and (3) the temperature was $25^{\circ}C$. The test results show that $Si_3N_4$ ceramics have a friction coefficient of about 1.0 and a wear loss of about 0.02 mm. Of the specimens used this study, the test specimen with 1.3 wt% of added $SiO_2$ nanocolloid has the best wear resistance because it has the lowest friction coefficient and the smallest wear loss. This specimen also has the highest Vickers hardness and bending strength. In this study, the friction coefficient is inversely proportional to the hardness and bending strength.

치차의 윤활과 마찰손실

  • 편집실
    • Journal of the KSME
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    • v.25 no.2
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    • pp.153-157
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    • 1985
  • 치차의 마찰손실은 일반적으로 낮으나, 치면의 온도상승을 초래하여 마멸을 증대시키거나 치면의 강도를 저하시킨다. 이것은 결과적으로 치차의 강도(부하특성)에 직접적인 관계를 갖고 있기 때문에 마찰손실을 가능한 한 낮게 유지하여야 한다. 치차의 맞물림은 치면의 미끄름속도 미 끄름율, 곡율반경 및 하중이 맞물림중에 순간적으로 변하므로 해석이 간단하지 않다.

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Optimum Design of Journal Bearings considering the Wear Rate (마멸율에 관한 저널베어링의 최적설계)

  • 임오강;이왕진
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.15 no.1
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    • pp.155-164
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    • 2002
  • The journal bearings use in machine parts which move relative to each other and those reduce friction and wear of journals. The journal bearings are designed to operate in the hydyodynamic lubrication regime, but elastohydrodynamic lubrication nay occur if the pressures are too high or the running speeds are too low at machine elements. It is the phenomenon that the lubricant film is broken and some parts of surfaces are in rolling contact, so that wear will increase in mixed lubrication regime. The purpose of this study is to minimize the wear rate of journal bearings for extending machine life. The wear mate in mixed lubricated regime is selected as objective function because most of wear of the journal bearings develops in elastohydrodynamic lubrication. The journal bearings we represented by a bearing radius, shaft radius, and bearing width, but the bearing radius only is selected as design variables due to a bearing radius has an influence on friction loss, stability limit velocity, and film parameter, which are used as constraints. For numerical calculation, PLBA, that is a class of the RQP algorithm, is used.

Fiber-Optic Directional Coupler Using HF Wet-Etching (플루오린화 수소산의 습식식각법을 이용한 광섬유형 방향성 결합기)

  • Son, Gyeongho;Jung, Youngho;Yu, Kyoungsik
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.28 no.1
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    • pp.25-32
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    • 2017
  • In this paper, a fabrication method of low-loss tapered optical fibers coupler using hydrofluoric acid with surface tension driven is proposed. The proposed fabrication method is very simple compared to flame-based method, and shows low excess insertion losses compared to polishing method. The adiabatic-tapered structure along the coupling region of the coupler shows wavelength independent characteristic over the C-band in optical communication system, and will enable promising applications.

AN EVALUATION OF WEAR CHARACTERISTICS OF LIGHT-CURED RESTORATIVE COMPOSITES ON ENAMEL SURFACE (광중합형 복합레진과 법랑질간의 마모특성 평가)

  • Baik, Byeong-Ju;Lee, Seung-Young;Lee, Doo-Cheol;Kim, Jae-Gon
    • THE JOURNAL OF THE KOREAN ACADEMY OF PEDTATRIC DENTISTRY
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    • v.28 no.2
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    • pp.261-270
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    • 2001
  • This study was performed to evaluate wear characteristics of light-cured composites when opposed by human enamel. Seven light-cured restorative composites were selected and enamel cusps sectioned from premolars. All samples were stored in distilled water at $37^{\circ}C$ for 10 days. 68.6 N of weight was loaded during the test. The measurements of vertical loss of enamel cusps, weight loss and volume loss of composites, and SEM observations of the polished and abraded surfaces were made after 30,000 cycles. The results obtained were summarized as follows; 1. The highest hardness value of 70.4 was observed in the Spectrum group and the lowest value of 19.8 was observed in the Heliomolar group. Results of Tukey test showed that an overall significant difference was indicated except the Spectrum, Z100 and Clearfil AP-X groups(p<0.05). 2. Enamel showed the good abrasion resistance against the Heliomolar group of microfilled composite and the Palpique Toughwell group containing the submicron hybrid type spherical fillers. 3. The abrasive wear resistance of hybrid composites was improved with the decrease of mean particle size and hybrid of submicron particle fillers. 4. SEM observation of worn surfaces revealed the protrusion, attrition and missing of fillers, cracks developing and delamination in the matrix.

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