• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2009년도 춘계학술대회 논문집
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• pp.194-195
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• 2009

본 연구에서는 고속전단 강도에 표면 처리의 변화가 미치는 영향에 대해 연구하고자 하였다. 표면 처리를 ENIG, ENEPIG, OSP로 하여 고속전단시험을 수행하였다. 고속전단 결과 SAC105의 전단 강도 값은 ENIG가 가장 작았고, ENEPIG가 가장 높았다. SAC305의 전단 강도 값은 ENIG가 가장 작았고, OSP와 ENEPIG는 비슷한 값을 나타냈다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.192-195
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• 2004

Surface friction welding, SFW, is a newly developed solid state welding technology for joining of thin metal sheets. Workpieces are joined by frictional heat, shear deformation and plastic flow generated by friction between the rotating tool and surface of the workpiece. The SFW is an economical and environmentally conscious technology with high joining speed and excellent properties, and is expected to be used widely in various industries in the near future.

• Journal of Welding and Joining
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• 제19권3호
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• pp.317-324
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• 2001

This study deals with high power Nd:YAG laser welding of thin steels for small pressure vessels. Full penetration welding at the overlap joint was performed so as to assure sufficient weld strength. Results showed that mid-depth weld size reduced drastically with increasing the travel speed. Position of focus had little effect on the bead formation even though short focal system was used. However, the shape factor and the bead width had closely related with the position of focus. Based on the microstructural inspection, acceptable weld was obtained when the overlap clearance was controlled up to 20% of the base metal thickness. In the case that the joint contained more clearance than the critical value, both the tensile shear strength and the tear strength were reduced. Results also demonstrated that shielding gases were proved to play a key role as far as the bead formation characteristics was taken into consideration. Blowing dry air through 5mm in diameter nozzle produced narrower bead cross-section than that of argon or nitrogen shielding.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2977-2983
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• 2008

The combustion characteristics of a partially premixed flame in a dump combustor were studied to determine the effects of hydrogen enrichment in propane. Bluff-body was used for flame stabilization. Fuel mixtures containing a hydrogen mole fraction ranging from 0.1 to 0.5 were burnt at ambient pressure within a quartz chamber. Tests were carried out keeping the total reactant flow rate by adjusting the fuel and air flow rates. The fluctuations of pressure were measured by piezoelectric pressure sensor. The instantaneous flame structure and OH chemiluminescence images were described by High-speed Intensified Charged Coupled Device (HICCD) camera and Intensified Charged Coupled Device (ICCD) camera. The present results show that hydrogen enrichment in fuel changed the location of primary reaction zone from inner recirculation zone to turbulent shear layer and pressure signal. The reason is that chemical aspects take precedence over flow aspects in the hydrogen-enriched flame.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.193-196
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• 2006

Unlike external bonded plate or carbon fiber, the external unbonded strengthening has some advantages in speed and simplicity of installation. It is not required surface preparations and not affected by environmental conditions. A set of six laboratory tests on RC beams strengthened using the technique are reported, results compared with non-strengthened specimens. The main test parameters are the cross-sectional area of the high-tension bar and the distance of stirrups. Test result show that the beams reinforced are superior to reference specimens, especially for the strength and deformation capacity. Also, it is shown that good efficiencies can be achived in shear strength of the beam.

• Steel and Composite Structures
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• 제47권2호
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• pp.203-216
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• 2023

The composite beam connections often encountered fracture failure in the welded bottom flange joint, and a bottom flange bolted connection has been proposed to increase the deformation ability of the bottom flange joint. The seismic performance of the bottom flange bolted composite beam connection was suffered from both the composite action of concrete slab and the asymmetric load transfer mechanisms between top and bottom beam flange joints. Thus, this paper presents a comprehensive numerical study on the working mechanism of the bottom flange bolted composite beam connections. Three available modelling methods and a new modelling method on the flange-stud-slab interactions were compared. The efficient numerical modeling method was selected and then applied to the parametric study. The influence of the composite slab, the bottom flange bolts, the shear composite ratio and the web hole shape on the seismic performance of the bottom flange bolted composite beam connections were investigated. A hogging strength calculation method was then proposed based on numerical results.

• 구강회복응용과학지
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• 제23권3호
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• pp.249-257
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• 2007

State of problem : The use of zirconium oxide all-ceramic material provides several advantages, including a high flexural strength(>1000MPa) and desirable optical properties, such as shading adaptation to the basic shades and a reduction in the layer thickness. Along with the strength of the materials, the cementation technique is also important to the clinical success of a restoration. Nevertheless, little information is available on the effect of different surface treatments on the bonding of zirconium high-crystalline ceramics and resin luting agents. Purpose : The aim of this study was to test the effects of surface treatments of zirconium on shear bond strengths between bovine teeth and a zirconia ceramic and evaluate differences among cements Material and methods : 54 sound bovine teeth extracted within a 1 months, were used. They were frozen in distilled water. These were rinsed by tap water to confirm that no granulation tissues have left. These were kept refrigerated at $4^{\circ}C$ until tested. Each tooth was placed horizontally at a plastic cylinder (diameter 20mm), and embedded in epoxy resin. Teeth were sectioned with diamond burs to expose dentin and grinded with #600 silicon carbide paper. To make sure there was no enamel left, each was observed under an optical microscope. 54 prefabricated zirconium oxide ceramic copings(Lava, 3M ESPE, USA) were assigned into 3 groups ; control, airborne-abraded with $110{\mu}m$ $Al_2O_3$ and scratched with diamond burs at 4 directions. They were cemented with a seating force of 10 ㎏ per tooth, using resin luting cement(Panavia $F^{(R)}$), resin cement(Superbond $C&B^{(R)}$), and resin modified GI cement(Rely X $Luting^{(R)}$). Those were thermocycled at $5^{\circ}C$ and $55^{\circ}C$ for 5000 cycles with a 30 second dwell time, and then shear bond strength was determined in a universal test machine(Model 4200, Instron Co., Canton, USA). The crosshead speed was 1 mm/min. The result was analyzed with one-way analysis of variance(ANOVA) and the Tukey test at a significance level of P<0.05. Results : Superbond $C&B^{(R)}$ at scratching with diamond burs showed the highest shear bond strength than others (p<.05). For Panavia $F^{(R)}$, groups of scratching and sandblasting showed significantly higher shear bond strength than control group(p<.05). For Rely X $Luting^{(R)}$, only between scratching & control group, significantly different shear bond strength was observed(p<.05). Conclusion : Within the limitation of this study, Superbond $C&B^{(R)}$ showed clinically acceptable shear bond between bovine teeth & zirconia ceramics regardless of surface treatments. For the surface treatment, scratching increased shear bond strength. Increase of shear bond strength by sandblasting with $110{\mu}m$ $Al_2O_3$ was not statistically different.

• 마이크로전자및패키징학회지
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• 제21권4호
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• pp.97-103
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• 2014

다양한 무연솔더합금 가운데 Sn-58Bi solder는 저융점이며 상대적으로 높은 인장강도를 갖고 있지만 취성적이라는 단점을 갖고 있다. 이러한 Sn-58Bi 솔더의 기계적 강도를 보완하기 위해 epoxy를 함유한 Sn-58Bi 솔더가 연구되어져왔다. 본 연구는 Sn-58Bi 솔더와 Sn-58Bi 에폭시 복합솔더를 이용하여 PCB 기판에 접합한 후, 시효처리에 따른 솔더/기판 계면 미세구조와 기계적 특성변화를 연구하였다. OSP 표면처리된 PCB 기판에 솔더볼을 형성 한 후 85, 95, 105, $115^{\circ}C$에서 100~1000 시간동안 시효처리하였으며, 기계적 특성평가로 저속전단시험을 진행하였다. 시효 처리 시간 및 온도의 증가에 따라 Cu6Sn5 금속간화합물층은 성장하였으며 Sn-58Bi 솔더 금속간화합물층이 Sn-58Bi 에폭시 복합솔더보다 두꺼웠다. 전단시험 결과, Sn-58Bi 에폭시 복합솔더가 Sn-58Bi 솔더보다 약 2배 높은 전단강도 값을 나타냈으며 시효시간이 증가할수록 전단강도 값은 감소하였다.

• 치위생과학회지
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• 제13권3호
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• pp.290-295
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• 2013

본 연구는 심미 치과보철물에 사용되는 지르코니아, lithium disilicate 코어와 전장도재 사이의 전단결합강도를 측정하고, 금속도재관을 대조군으로 설정하여 비교하였다. 직사각기둥 모양의 시편을 각각 10개씩 제작하여 코어와 전장도재 사이의 전단결합강도를 측정한 후 파절면의 양상을 실체현미경을 통해 관찰하였다. 제한된 조건하에 시행된 실험을 통하여 심미보철 분야에 널리 적용되고 있는 치과용세라믹 코어의 전단결합강도를 확인하였으며, 측정 후 비교분석된 결과는 다음과 같다. 2종의 치과용 세라믹 코어와 전장도재 간에 전단결합강도는 금속도재관의 전단결합강도와 유의한 차이가 있었다 (p<0.05). 본 실험 결과를 토대로 ZB군은 임상적으로 받아들여지는 전단결합강도 범위 내 분포를 보이지만, LB군은 임상허용 범위에 못 미치는 결과값을 보였다. 금속도재관과 달리 지르코니아, lithium disilicate 전부도재관은 모두 혼합형 파절양상을 보였다. 결론적으로 전단결합강도 실험에 사용된 시편이 임상적인 치과보철물의 형태와는 달리 실험을 위한 시편의 형태로 제작되어 임상적 결과를 반영하지 못했으며 구강 내의 상황과도 다르다는 한계점을 가지고 있다. 추후에는 이를 보완하여 치과보철물과 유사한 형태의 시편을 이용한 전단결합 강도의 측정과 구강 내 조건을 고려한 추가 실험이 필요하다고 생각된다.

• 한국구조물진단유지관리공학회 논문집
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• 제26권3호
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• pp.11-20
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• 2022

이 연구의 주요 목적은 고속철도 콘크리트 궤도 슬래브의 콘크리트 슬래브(track concrete layer, TCL)와 도상안정층(hydraulically stabilized based course, HSB) 사이 층분리를 평가하기 위한 비파괴검사법으로 전단파 토모그래피 기술의 활용가능성을 실험적으로 확인하는 것이다. 이를 위하여 다채널 전단파 측정 장치(MIRA)를 활용하여 실물 크기로 제작된 고속철도 콘크리트 궤도 슬래브 실험체 내부의 층분리 결함을 평가하였다. 실물실험체는 Rheda 2000 시스템에 따라 설계 및 시공되었으며, 노반 위에 HSB를 타설하고, 그 위에 TCL이 타설된 2층 슬래브 구조를 갖는다. 실물실험체는 일부구간의 HSB상부에 스티로폼으로 제작된 인공결함(가로 및 세로가 각각 400mm이고 두께가 각각 5mm, 15mm인 압출폴리스티렌폼(XPS)보드 2개)을 삽입하여, TCL과 HSB 사이에 층분리 결함이 생기도록 시공하였다. 시험체의 층분리 구간에서 얻은 콘크리트 단층이미지는 층분리에 따른 균열 및 HSB와 지반사이의 계면에서 반사되는 신호를 효과적으로 보여 주었다. 한편 초음파 토모그래피 이미지에서 TCL 콘크리트의 매입물(철근, 트러스, 인서트 등)에서 반사된 신호와 층분리 결함 신호를 구분하기 위한 노이즈 제거를 위한 이미지 처리방법을 적용하여 층분리 결함을 효과적으로 분리하였다. 토모그래피 이미지에서 추출된 층분리 결함의 크기정보와 공간정보를 통합하여 층분리 지도로 재구성하였으며, 층분리 결함의 위치 및 크기를 시각화하는데 효과적인 것을 확인하였다.