• Restorative Dentistry and Endodontics
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• 제17권1호
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• pp.191-205
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• 1992

The purpose of this study was to evaluate the microleakage of class II composite resin inlays and compare them with the conventional light-cured resin filling restorations. Class II cavities were prepared in 60 extracted human molars with which cervical margins were located below 1.0mm at the cemento-enamel junction using No. 701 tapered fissure carbide bur. All of the prepared cavities were restored as follows and divided into 6 groups. Group I and 2 were restored using direct filling technique and group 3,4,5 and 6 were restored using direct inlay technique that was cemented with dual-cured resin cements. group I: Cavities were restored with light-curing composite resin, Brilliant Lux. group 2. Cavities were restored with light-curing composite resin, Clearfil PhotoPosterior. group 3: Cavities were restored with Clearfil CR Inlay and heat treated at $125^{\circ}C$ for 7 minutes. group 4: Cavities were restored with same material as group 3 and heat treated at $100^{\circ}C$ for 15 minutes. group 5: Cavities were restored with Brilliant (Indirect esthetic system) and heat treated at $125^{\circ}C$ for 7 minutes. group 6: Cavities were restored with same material as group 5 and heat treated at $100^{\circ}C$ for 15 minutes. All specimens were polished with same method and thermocycled between $6^{\circ}C$ and $60^{\circ}C$, then immersed in a bath of 2.0% aqueous solution of basic fuchsin dye for 24 hours. Dyed specimens were sectioned longitudinally and dye penetration degree was read on a scale of 0 to 4 by Tani and Buonocore's method 45). The results were as follows: 1. Microleakage was observed rather at the cervical margins than at the occlusal margins in all groups. 2. Composite resin inlay groups showed significantly less leakage than direct filling groups at the cervical margins (p < 0.001). 3. In composite resin inlay groups, there was no significant difference in microleakage between specimens by heat treating temperature and time (p > 0.05). 4. There was no significant difference in leakage between each groups at the occlusal margins (p > 0.05).

• Journal of Welding and Joining
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• 제28권3호
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• pp.49-58
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• 2010

Various alloy system, such as Cu-Sn-Ti, Cu-Ag-Ti, and Ni-B-Cr-based alloy are used for the brazing of diamond grits. However, the problem of the adhesion strength between the diamond grits and the brazed alloy is presented. The adhesion strength between the diamond grits and the melting filler alloy is predicted by the contact angle, thereby, instead of diamond grit, the study on the wettability between the graphite and the brazing alloy has been indirectly executed. In this study, Cu-13Sn-12Ti filler alloy was manufactured, and the contact angles, the shear strengths and the interfacial area between the graphites (diamond grits) and braze matrix were investigated. The contact angle was decreased on increasing holding time and temperature. The results of shear strength of the graphite joints brazed filler alloys were observed that the joints applied Cu-13Sn-12Ti alloy at brazing temperature $940^{\circ}C$ was very sound condition indicating the shear tensile value of 23.8 MPa because of existing the widest carbide(TiC) reaction layers. The micrograph of wettability of the diamond grit brazed filler alloys were observed that the brazement applied Cu-13Sn-12Ti alloy at brazing temperature $990^{\circ}C$ was very sound condition because of existing a few TiC grains in the vicinity of the TiC layers.

• 한국산업융합학회 논문집
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• 제26권2_2호
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• pp.341-347
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• 2023

The subway is one of the most common and important means of transportation in modern society. In order to use the subway safely, tracks are necessary, but trains are prone to derailment and collisions. In order for the train to run safely on the track, the fishplate that connects the line connection is used. The damaged railway was a fishplate for connecting subway lines used for 11 years, and damage analysis and countermeasures were presented. Beach marks were observed on both fracture surfaces, and striations appeared at the range of crack propagation. The damaged part is Cr carbide, which has a higher hardness than the base metal, and is judged to be embrittled and destroyed by fatigue. The SM50C fishplate was subjected to a cyclic stress of about 59% of the upper limit of tensile-compression fatigue limit, but inclusions were the cause of failure. In order to prevent fatigue failure of the SM50C steel fishplate, the occurrence of inclusions should be minimized and processed to have a homogeneous structure when manufacturing the fishplate. In addition, compressive residual stress is given through surface modification such as peening to control crack generation. It is necessary to minimize the change in shape that can become a stress concentration part along with accurate fastening of the bolt, and to design the stress distribution to be as uniform as possible.

• 한국주조공학회지
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• 제38권5호
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• pp.103-110
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• 2018

코발트기 주조용 초내열합금 X45를 이용하여 다양한 형태의 열처리에 따른 미세조직과 기계적 특성의 변화에 대하여 고찰한 결과를 요약하면 다음과 같다. 1) 합금의 응고 시 결정립계와 수지상간 경계를 따라 Cr이 다량 함유된 조대한 $M_{23}C_6$ 탄화물과 W과 Co의 함량이 높은 $M_6C$ 탄화물이 형성되어 있었고, $1274^{\circ}C$에서 용체화 처리하면 대부분의 탄화물이 용해되었다. $1150^{\circ}C$에서의 용체화 처리 동안 일부 결정립계 탄화물이 용해되지만 공정탄화물 근처에서 새로운 탄화물의 석출이 일어났다. $927^{\circ}C$와 $982^{\circ}C$에서 시효처리만 했을 때 용체화 처리 후 시효처리 한 시편 보다 공정 탄화물 근처에서 석출되는 탄화물의 양이 많았고, 크기가 작았다. 2) $1150^{\circ}C$에서 용체화 처리한 후 시효처리 하면 경도의 증가가 뚜렷하지 않으며, $927^{\circ}C$와 $982^{\circ}C$에서 시효처리만 했을 때 다량의 매우 미세한 탄화물의 석출에 의하여 경도의 증가 폭이 더 컸다. 상온 항복강도는 $927^{\circ}C$에서 시효처리 했을 때 가장 컸지만 인장강도와 연신율은 $982^{\circ}C$에서 12시간 시효처리 했을 때 가장 컸다. 고온 크리프 특성은 $982^{\circ}C$에서 12시간 시효처리 했을 때 가장 우수하였다. 3) 장시간 고온 노출 되는 동안 탄화물의 석출과 성장이 일어났고, 8000시간 고온에서 노출시킨 시편에서는 수지상 중심부에도 탄화물이 석출되어 크리프 파단 수명이 증가하였다.

• 대한치과보철학회지
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• 제53권4호
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• pp.295-300
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• 2015

목적: 레진과 니켈-크롬 합금의 결합력에 미치는 금속 프라이머 및 다용도 접착제의 영향에 대하여 비교 평가하고자 한다. 재료 및 방법: 실험을 위해 120개의 니켈-크롬 합금(Vera Bond 2V) 디스크를 제작하여 아크릴 레진 실린더에 포매하였다. 시편의 표면은 220 grit, 600 grit의 실리콘 카바이드지로 연마한 뒤 $50{\mu}m$의 알루미늄옥사이드 입자를 분사하여 처리하였다. 실험군은 메탈 프라이머의 적용(Metal primer II, Alloy primer, Metal & Zirconia primer, MKZ primer)과 다용도 접착 시스템(Single Bond Universal, All Bond Universal)에 따라 6개 군으로 나뉘었다. 각 시편의 중앙에 높이 2 mm, 직경 3 mm로 복합레진을 충전하였으며, 제작된 모든 시편은 $37^{\circ}C$ 증류수에서 24시간 보관하였다. 만능시험기에 시편을 위치시킨 후 1 mm/min cross head speed로 전단결합강도를 측정하였다. 통계분석은0.05의 유의수준으로 일원분산분석을 시행하였고 Tukey's multiple coMParison test로 사후검정을 하였다. 결과: Single Bond Universal, All Bond Universal, Metal Primer II 3개 군과 Alloy Primer, MKZ Primer, Metal & Zirconia Primer 3개 군 사이에 통계학적으로 유의한 차이를 보였다(P<.001). 결론: 니켈-크롬 합금에 대한 다용도 접착 시스템의 전단결합강도는 Metal Primer II를 제외한 기존의 금속 프라이머를 적용했을 때 보다 높게 나타났다. 본 실험에서 더 나아가 다용도 접착 시스템 내 실란(Silane) 포함 여부에 따른 효과를 평가할 수 있는 연구가 필요할 것이다.