• 제목/요약/키워드: Diamond saw

검색결과 126건 처리시간 0.042초

Pe-Co-Ni 분말 소결 금속과 탄소강의 이종재료간 레이저 용접부의 결함형성기구 연구 (A Study on the Formation Mechanism of Discontinuities in $CO_2$ Laser Fusion Zone of Fe-Co-Ni Sintered Segment and Carbon Steel)

  • 신민효;김태웅;박희동;이창희
    • Journal of Welding and Joining
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    • 제21권3호
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    • pp.58-67
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    • 2003
  • In this study, the formation mechanism of discontinuities in the laser fusion zone of diamond saw blade was investigated. $CO_2$ laser weldings were conducted along the butt between Fe base sintered tip and carbon steel shank with sets of variable welding parameters. The effect of heat input on irregular humps, outer cavity, inner cavity and bond strengh was evaluated. The optimum heat input to have a proper humps was in the range of 10.4~$17.6kJm_{-1}$. With increasing heat input, both outer and inner cavities were reduced. The outer cavity was caused by insufficient refill of keyhole, while inner cavity was caused by trapping of bubble in molten metal. The bubble came from sintered tip and intensive vaporization at bottom tip of the keyhole. A gas formation and low melting point element vaporization were not occurred during welding. We could not find any relationship between bond strength and amount of discontinuities. Because the fracture were occurred in not only sintered tip but also carbon steel shank due to hardness distributions.

소결체와 저탄소강의 레이저용접 특성에 미치는 입열량 및 용접부 성분변화의 영향 (Influence of Heat Input and Weld Bead Composition on Welding Property in the Laser Welding between Sintered Segment and Mild Steel Shank)

  • 정우광;조남준;김성욱;이창희;김승대;이주형;박화수
    • 한국재료학회지
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    • 제14권6호
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    • pp.425-431
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    • 2004
  • A laser welding was applied between sintered tip of Fe-Co-W and low carbon steel shank for the diamond saw blade. The welding characteristics and formation of defects were investigated carefully for the weld fusion zone in different welding condition. Dendrite arm spacing in weld bead decreased with decrease of heat input. Co and W increased and Fe decreased in the weld fusion zone with increase of the heat input. The corresponding change of composition was observed with the change of beam position. The maximum and total length of crack decreased with increase of the heat input. The crack in weld bead was propagated along the dendrite boundary and was caused mainly by the segregation of constituent during the solidification.

상아질에 대한 광중합형 글라스 아이오노머 시멘트의 접합도 (ADAPTATION OF RESIN-MODIFIED GLASS IONOMER CEMENT TO DENTIN)

  • 조영곤
    • Restorative Dentistry and Endodontics
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    • 제22권2호
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    • pp.792-800
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    • 1997
  • The purpose of this study was to evaluate the adaptation of self-cured glass ionomer cement and resin-modified glass ionomer cement and polyacid-modified resin composite, which are light-cured giass ionomer cements, to dentin surface. Twelve extracted human maxillary and mandibular molar teeth were used in this study. The entire occlusal dentin surfaces of teeth were exposed with Diamond Wheel Saw and smoothed with sand papers (300, 600, 1200grits). They were randomly assigned into 3 groups according to glass ionomer cements used; Control group- Fuji II, Expeimental group 1 - Fuji II LC, Expeimental group 2 - Dyract. According to the manufacturer's directions, three glass ionomer cements were bonded to exposed dentin surfaces of the tooth crown and cured. Crowns and glass ionomers were trimmed after 24hrs and sectioned horizontally and vertically with diamond saw. The interface of glass ionomer cements and dentin was examined under SEM. The results were as follows : 1. Good adatation between glass ionomer cement and dentin on the horizontal section was showed in control and experimental group 1, but the gap of $20{\mu}m$, which was observed distinct separation between glass ionomer cement and dentin, was showed in experimental group 2. 2. Good adatation between glass ionomer cements and dentin on the vertical section was showed in control and experimental group 1, but the gap of 80-$100{\mu}m$ was showed in experimental group 2. 3. Cohesive fracture within glass ionomer cements in control and experimental group 1 was showed, but no cohesive fracture was showed in experimental group 2.

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인공절리를 이용한 심발 발파에서의 지반진동 비교 (A Comparison of Ground Vibration in Center Cut Blasting using Artificial Joints)

  • 박훈;석철기;노유송
    • 화약ㆍ발파
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    • 제36권4호
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    • pp.16-25
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    • 2018
  • 터널 굴착시 지반진동을 감소시키기 위해 굴착면에 부분적인 자유면을 형성하고 제어발파를 수행하는 자유면 발파공법이 적용되어 왔다. 본 연구에서는 다이어몬드 와이어 쏘를 이용하여 인공절리를 심발부에 형성하고, 심발부 발파 시 발생되는 지반진동을 비교함으로써 인공절리에 의한 지반진동 감소를 평가하였다. 해석 결과, 일반 심발발파보다 인공절리 심발발파에서 지반진동이 감소하였으며, 수직 인공절리 심발발파보다 수평 인공절리 심발발파에서의 지반진동 감소 효과가 더 크게 평가되었다.

소결밀도에 따른 분말 소결금속과 탄소강의 이종금속 레이저 용접성 고찰 (The Study of Laser Weldability of two different Metal, Carbon Steel and Sintered Materials, Depends on the Sintered Density)

  • 김용;양현석;박기영;이경돈
    • 한국레이저가공학회지
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    • 제11권2호
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    • pp.8-14
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    • 2008
  • Sintered specimen which used for a blade of diamond tool was manufactured in order to verify $CO_2$ laser weldability depend on sintered temperature. Five kind of specimen were prepared and the range of temperature is from $600^{\circ}C$ to $1000^{\circ}C$ at intervals of $100^{\circ}C$. As a result of the sintered density test, the porosity rate appeared in the range of $2.1%{\sim}21.4%$. After welding, the most segments had exceeds the minimum fracture stress (600MPa, The Standard Safety of Europe) at the welding strength test except on the sintered at $600^{\circ}C$. In case of the sintered at $700^{\circ}C$, even satisfied the safety allowable stress but cannot get the good quality for bead appearance because of humping defect. In the conclusion, we could know that it showed not only relatively soundness bead but also enough welding strength when the sintered blade of diamond tool is included less than 4% of porosity rate.

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Effect of dentin surface roughness on the shear bond strength of resin bonded restorations

  • Koodaryan, Roodabeh;Hafezeqoran, Ali;Poursoltan, Sajjad
    • The Journal of Advanced Prosthodontics
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    • 제8권3호
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    • pp.224-228
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    • 2016
  • PURPOSE. This study aimed to investigate whether dentin surface preparation with diamond rotary instruments of different grit sizes affects the shear bond strength of resin-bonded restorations. MATERIALS AND METHODS. The buccal enamel of 60 maxillary central incisors was removed with a low speed diamond saw and wet ground with silicon carbide papers. The polished surfaces of the teeth were prepared with four groups of rotary diamond burs with super-coarse (SC), coarse (C), medium (M), and fine (F) grit sizes. Following surface preparation, 60 restorations were casted with nickel-chromium alloy and bonded with Panavia cement. To assess the shear bond strength, the samples were mounted on a universal testing machine and an axial load was applied along the cement-restoration interface at the crosshead speed of 0.5 mm/min. The acquired data was analyzed with one way ANOVA and Tukey post hoc test (${\alpha}=.05$). RESULTS. The $mean{\pm}SD$ shear bond strengths (in MPa) of the study groups were $17.75{\pm}1.41$ for SC, $13.82{\pm}1.13$ for C, $10.40{\pm}1.45$ for M, and $7.13{\pm}1.18$ for F. Statistical analysis revealed the significant difference among the study groups such that the value for group SC was significantly higher than that for group F (P<.001). CONCLUSION. Dentin surface roughness created by diamond burs of different grit sizes considerably influences the shear bond strength of resin bonded restorations.