• 한국정밀공학회지
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• 제24권4호
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• pp.93-101
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• 2007

Aluminum alloy which is one of the light materials has been tried to apply to light weight vehicle body. In order to do that, welding technology is very important. In case of the aluminum laser welding, the strength of welded part is reduced due to porosity, underfill, and magnesium loss. To overcome these problems, laser welding of aluminum with filler wire was suggested. In this study, experiment about laser welding of AA5182 aluminum alloy with AA5356 filler wire was performed according to process parameters such as laser power, welding speed and wire feed rate. The tensile strength was measured to find the weldability of laser welding with filler wire. The models to estimate tensile strength were suggested using three regression models and one neural network model. For regression models, one was the multiple linear regression model, another was the second order polynomial regression model, and the other was the multiple nonlinear regression model. Neural network model with 2 hidden layers which had 5 and 3 nodes respectively was investigated to find the most suitable model for the system. Estimation performance was evaluated for each model using the average error rate. Among the three regression models, the second order polynomial regression model had the best estimation performance. For all models, neural network model has the best estimation performance.

• 한국해양공학회지
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• 제29권6호
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• pp.481-487
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• 2015

The effects of the heat input and preheat/interpass temperatures on the tensile strength and impact toughness of multipass welded weld metal were investigated and interpreted in terms of the recovery of the alloying elements and microstructure. Increases in both the heat input and preheat/interpass temperatures decreased the tensile strength of the weld metal. A lower recovery of alloying elements, especially Mn and Si, and smaller area fraction of acicular ferrite in the weld metal were observed in higher heat input welding, resulting in a lower tensile strength. In contrast, only a microstructure difference was observed at a higher preheat/interpass temperature. The impact toughness of the weld metal gradually increased with an increase in the heat input because of the lower tensile strength. However, it decreased again when the heat input was larger than 45 kJ/cm because of the much smaller area fraction of acicular ferrite. No effect of the preheat/interpass temperature on the impact toughness was observed. The formation of a weld metal heat-affect zone showed little effect on the impact toughness of the weld metal in this experiment.

• 한국산학기술학회논문지
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• 제4권1호
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• pp.42-46
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• 2003

섬유 코팅제로 널리 쓰이고 있는 액상 PVC는 여러 가지 특성 중 무광택 효과가 뛰어나지만 코팅된 섬유 표면의 유연성이 감소된다. 이런 결함을 대체할 수 코팅 물질로 Elastomer계열의 액상 실리콘 고무를 사용했다. 기존 액상 PVC공정과 동일하게 진행했으며, 로울러의 압축력과 공정상의 예비경화를 이용했다. 실험 결과 액상 PVC로 코팅된 직물의 경도는 70E, 인장강도는 10.3 MPa, 신율은 200%로 측정되었다. 액상 실리콘 고무로 코팅된 직물의 경도는 40도, 인장강도는 5.1 MPa, 신율은 460%,였다. 따라서 액상 실리콘 고무 코팅은 3차 가공 없이 액상 PVC 코팅보다 플라스틱 직물 표면의 무광택성과 유연성을 증가시켰다.

• Journal of Chest Surgery
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• 제22권3호
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• pp.373-383
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• 1989

Glutaraldehyde is known as an ideal preservatives for pericardial heterograft, and many laboratories used this chemicals for preparing tissue valves, pericardial patches and MVOP [monocusp ventricular outflow patch] so we tried to find out the appropriate concentration and ingredients of the Glutaraldehyde for the preparing bovine pericardium. We selected 50 calves, aged about 2 years, and procured their pericardia. These were divided 6 groups such as fresh group, treated with only antibiotics, treated with Glutaraldehyde 0,5%, 0.625 %, 0.75 %, and 0.875 %, and our experiments included microbial culture test, tensile strength measurement and microscopic examination. On microbial culture, there were no growth on 1 week and 4 weeks after preparation with all kind of Glutaraldehyde, but on 4 weeks after only antibiotics treatment [Penicillin, Streptomycin, Kanamycin, Amphotericin -B] E.coli and candida albicans were observed. On tensile strength test, 0.625 % and 0.75 % Glutaraldehyde were revealed as the best preservatives for bovine pericardium and compared to other commercial products they kept more desirable tensile strength. On light and electron microscopic examinations, Glutaraldehyde treated pericardia had much regular and compact collagen fibers and preserved more normal structures, but there were no difference between the different concentration of the Glutaraldehyde. We concluded that 0.625% and 0.75 % Glutaraldehyde were the best concentration for preservation of bovine pericardium in our experiment.

• 열처리공학회지
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• 제4권1호
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• pp.37-41
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• 1991

In this study, the effect of solution treatment temperature on the tensile property in intermediate thermo-mechanical treated Al-Li alloys are investigated. After the intermediate thermo-mechanical treated Al-Li, Al-Li-Mg and Al-Li-Mg-Zr alloys were solution treated at various temperatures (500, 520 and $540^{\circ}C$), these were aged at $190^{\circ}C$, $240^{\circ}C$ and tested tensile properties. The results obtained from the experiment are as follows ; 1) The optimum solution heat-treatment temperature is $540^{\circ}C$ for a Al-Li alloy, and the recrystallized grain size is about $70{\mu}m$. 2) The optimum solution heat-treatment temperature is $500^{\circ}C$ for a Al-Li-Mg alloy, and the recrystallized grain size is the most coarse in all alloys. 3) The tensile property is independent of the solution treatment temperature in a Al-Li-Mg-Zr alloy, and the recrystallized grain size is the finest owing to addition of Zr.

• 대한치과보철학회지
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• 제28권2호
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• pp.53-76
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• 1990

The purpose of this study was to evaluate the tensile bond strength of adhesive resins to successively recast Rexillium III and Degudent-U. Recasting was done 4times successively. Specimen $A_1$, were cast by new metal, and $A_2$ by surpus of $A_1$, $A_3$ by surplus of, $A_2$ $A_4$ by surplus of $A_3$, $A_5$ by surplus of $A_4$ plus 50% new metal. The types of surface treatment for resinbonded restoration in this experiment were electrolytic etching by OXY-ETCH(Oxy dental products, Inc., Hillside, New Jersey, U.S,A.), aluminum oxide blasting, anodic oxidation by EZ-OXISOR( Towagiken Co., Kyoto, Japan), electrotinplating by Kura Ace(Kuralay Co., Kyoto, Japan). Three kinds of cementing resin used in this study were Comspan(K.P. Cauil Co, Milford Delaware, U.S.A.), Super Bond C&B(Sun-Medical Co. Ltd., Kyoto,Japan), Panavia EX(Kuralay Co., Ltd., Osaka, Japan). Tensile bond strength was measured by Instron Universal testing machineModel 1125) and all the specimen were observed with SEM(JEOL, JSM-T2000) and mode of bond failure were recorded. The obtained results were as follows : 1. In electrolytic etched group, tensile bond strength was decreassed when recast alloy was used, and tensile bond strength of Compan and panavia EX were not significantly different(P>0.05). 2. In remaining group treated by aluminum oxide blasting, EZ-OXIOR, Kura Ace, tensile bond strength were not changed when recast alloy were used, and tensile bond strength of SuperBond(C&B and Panavia EX were not significantly different(P>0.05). 3. IN SEM evaluation, electrolytic etched group and electrotinplated group exhibited different image when recast alloy was used, and remaining groups treated by aluminum oxide blasting, EZ-OXISOR exhibited the same. 4. IN observation of bond failure, electrolytic etched group exhibited adhesive failure and remaing groups treated by aluminium oxid blasting, EZ-OXISOR, Kura Ace exhibited adhesive and cohesive failure.

• 대한치과보철학회지
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• 제25권1호
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• pp.303-316
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• 1987

The purpose f this study was to evaluate the effect of resin film thickness on the tensile bond strength and to compare the tensile bond strengths of 4 differently treated metal surfaces. For the experiment, seventy metal specimens were cast with Verabond and divided into I, II, III, groups. The metal specimens in group I were electrolytically etched and cemented with Panavia under finger pressure. Cement film thickness was regulated with metal spacers. The metal specimens in Group II were treated by 4 methods, such as electrolytic etching method, salt-roughened method, EZ-oxisor method , chemical etching method and cemented with Panavia. In group III, electrolytically etched metal specimens were cemented with Hy-Bond. The etched surface of metal specimens and the cement film thickness were examined under the scanning electron microscope. Results were as follows; 1. The tensile bond strength showed no significant difference between $30{\mu}m,\;80{\mu}m,\;130{\mu}m$ film thicknessspecimens. 2. There was no significant difference in the tensile bond strength between the 4 differently treated metal specimens. 3. The tensile bond strength showed significant difference between Panavia and Hy-Bond. 4. Scanning electron microscope photograph revealed that tile interdendritic eutectic was removed in electrolytically etched metal surfaces hilt even dendritic arm was removed in Chemically etched metal surfaces. 5. The metal surfaces which were air-abraded with $50{\mu}m$ aluminum oxide showed roughness and small crack on scanning electron microscope photograph.

• 조명전기설비학회논문지
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• 제13권4호
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• pp.120-126
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• 1999

수명예측을 하기 위한 기초자료로 ACSR의 기계적 시험의 일종인 인장시험이 필요하다. 이 인장시험의 결과들이 경년 변화에 대해 어떤 상관관계가 있는가를 파악하여 통계적으로 처리함으로써 수명예측을 해 볼 수 있다. 통계적 처리기법으로는 회귀분석 방법이 일반적이다. 본 연구에서는 ACSR의 인장시험을 건전 전선과 수거된 경년 변화를 갖는 전선에 대해 실시하였다. 수명예측의 한계는 캐나다 Ontario Hydro Research의 기준인 정격 인장강도의 20[%] 손실점을 택하였다. 본 연구에 이용된 ACSR의 규격은 $95[\textrm{mm}^2]$, $97[\textrm{mm}^2]$, $120[\textrm{mm}^2]$, $240[\textrm{mm}^2]$ 를 대상으로 하여 선형회귀분석과 비선형 회귀분석을 실시하여 예측수명을 제시하였다. 분석프로그램으로는 SPSS와 Matlab의 Statistics Toolbox를 이용하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 춘계학술대회 논문집
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• pp.833-834
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• 2008

• Design & Manufacturing
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• 제15권2호
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• pp.23-29
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• 2021

The specific strength of magnesium alloy is four times that of iron and 1.5 times that of aluminum. For this reason, its use is increasing in the transportation industry which is promoting weight reduction. At room temperature, magnesium alloy has low formability due to Hexagonal closed packed (HCP) structure with relatively little slip plane. However, as the molding temperature increases, the formability of the magnesium alloy is greatly improved due to the activation of other additional slip systems, and the flow stress and elongation vary greatly depending on the temperature. In addition, magnesium alloys exhibit asymmetrical behavior, which is different from tensile and compression behavior. In this study, a jig was developed that can measure the plane deformation behavior on the surface of a material in tensile and compression tests of magnesium alloys in warm temperature. A jig was designed to prevent buckling occurring in the compression test by applying a certain pressure to apply it to the tensile and compression tests. And the tensile and compressive behavior of magnesium at each temperature was investigated with the developed jig and DIC equipment. In each experiment, the strain rate condition was set to a quasi-static strain rate of 0.01/s. The transformation temperature is room temperature, 100℃. 150℃, 200℃, 250℃. As a result of the experiment, the flow stress tended to decrease as the temperature increased. The maximum stress decreased by 60% at 250 degrees compared to room temperature. Particularly, work softening occurred above 150 degrees, which is the recrystallization temperature of the magnesium alloy. The elongation also tended to increase as the deformation temperature increased and increased by 60% at 250 degrees compared to room temperature. In the compression experiment, it was confirmed that the maximum stress decreased as the temperature increased.