• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.3
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• pp.243-249
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• 2016

The present work is for an evaluation of resistance to corrosion in steel coated with cementitious repair material, so that 3 cases of steel plate(Normal, Welding, Welding & coating case) are subjected to ICM(Impressed Current Method) for acceleration of corrosion for 7days. Tested and estimated corrosion ratio through Faraday's Law are compared, and the related flexural strength are evaluated. In Normal and Welding cases, similar level of corrosion ratio(70%) is evaluated, however only 17% level of corrosion ratio is evaluated in the Welding & coating case, which indicates that cementitious repair material is effective to anti-corrosion due to a block of chloride penetration. The flexural test results are consistent with those in accelerated corrosion test, which shows a significant flexural strength in Welding & coating case by 3.4times greater than the others. The cementitious material repair coating is evaluated to be effective to anti-corrosion in welding of steel plate.

• The Journal of Korean Academy of Prosthodontics
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• v.25 no.1
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• pp.363-378
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• 1987

도재소부전장관에서 금속이 노출되지 않고 도재만이 파절시, 구강내에서 직접 행할 수 있는 심미적 수복 방법으로서 복합성 수지를 이용한 수복 방법이 널리 이용되고 있는데 본실험의 목적은 도재와 광중합성 수지간의 접합강도를 비교 측정코저 함에 있다. 본 실험에서는 주사전자 현미경을 사용하여 도재의 부식액 (5% 불화수소산용액, Excelco's porcelain etching gel) 및 부식 시간(2.5분, 5분, 10분, 20분)에 따른 부식양상을 먼저 관찰하였다. 그다음 각기 다른 시간에서 부식 처리된 도재와 대조군으로서 미부식 처리된 도재에 광중합성 수지를 부착시킬시, 첫째 Silane coupling agent(Scotch-Prime)도포후 광중합성 수지를 결합 시켰고 둘째 bonding agent(Scotch bond)도포후 광중합성 수지를 결합시켰으며 셋째 Silane coupling agent(Scotch-Prime)에 bonding agent(Scotch bond)를 도포후 광중합성 수지로 결합 시킨후, 인장강도 측정기 (Shimadzu universal testing machine)를 사용하여 결합력을 측정한 결과 다음과 같은 결론을 얻었다. 1. 부식처리된 도재가 미부식 처리된 도재 보다 결합력이 높았다. (p<0.05, P<0.001) 2. 부식 처리된 도재나 미부식 처리된 도재에 있어서 silane coupling agent 도포후 bonding agent로 처치한 경우 가장 결합력이 높았으며 그다음 silane coupling agent로 처치한 경우, bonding agent로 처치한 경우의 순이었다. 3. 도재부식 시간의 증가에 따른 결합력의 차이는 5% HF용액으로 부식 처리된 도재와 Excelco로 부식 처리된 도재에 있어서 5분 정도 까지는 결합력의 증가를 보였으나 그 후에는 결합력에 있어서 거의 증가하지 않는 양상을 보였다. 4. Excelco로 부식 처리된 도재와 5% HF 용액으로 부식처리된 도재간의 결합력 차이에 있어서 bonding agent만으로 처치한 경우에는 두결합력 사이에 서로 유의한 차이를 보이지 않았으나 (P>0.5) silane coupling agent만으로 처치한 경우와 silane coupling agent 도포후 bonding agent로 처치한 경우에는 두결합력 사이에 서로 유의한 차이를 보였다. (P<0.05, P<0.001) 5. Excelco로 부식처리된 도재가 5% HF 용액으로 부식처리된 도재보다 부식정도가 더 현저하였다.

• Journal of the Korean Society for Railway
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• v.12 no.5
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• pp.725-731
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• 2009

For structural design and diagnosis, quantitative relationship between corrosive degradation and variation of mechanical properties such as tensile strength and fatigue strength is needed. But it is difficult to find experimental data associated with corrosive degradation of structural structures in the literature. In this study, first of all I established the atmospheric corrosion test procedure. And using specimens of SM490A and SS400 on the atmospheric corrosion test bed, I carried out tensile and fatigue tests at regular intervals. And we studied the effect of post-weld heat treatment on the tensile and fatigue behaviour. It is found fatigue strength decreases as the atmospheric corrosion period increases.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.1
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• pp.105-112
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• 2008

The purpose of this study was to evaluate the contact angle made by 3 kinds of self etching primers (Clearfil SE Bond, AdheSE, and Tyrian) on dentin and to measure the microtensile bond strength of resin composite to dentin using these self-etching primers. Contact angle between each of 3 self etching primers and polished dentin surface was measured (n=30) by contact angle analyzer and the result was analyzed by One-way ANOVA. For the measurement of microtensile bond strength, polished dentin surface was treated with each of 3 self etching primers and dentin adhesives. Z-250 composite resin was built-up with a height of 5 mm on the adhesive-treated surface and light cured for 40s with a halogen light curing unit. Thereafter, each tooth was sectioned into slabs perpendicular to the bonded interface and trimmed (n=45). The microtensile bond strength was measured with universal testing machine and the result was analyzed with Kruskal-Wallis test. AdheSE group showed the highest contact angle followed by Clearfil SE group and Tyrian group (p<0.05). AdheSE group and Clearfil SE group showed significantly higher microtensile bond strength than Tyrian group (P<0.05).

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.8
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• pp.1503-1512
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• 1992

The strength evaluation and life prediction on the corrosion part of structure is one of the most important subjects, as a viewpoint of reducing economic loss by regular inspection, maintenance, repair and replace. For this purpose, it has been difficult to obtain the available data on growth of pit depth or growth rate of each pit which depends on time. In this paper, the life prediction and strength evaluation method was suggested for the structure with irregular stress concentration part by surface corrosion. The statistical distribution pattern of corrosion depth and the degree of fatigue strength decline were confirmed according to corrosion period by artificial corrosion of SS41 steel. The life prediction and the fatigue strength evaluation of materials with consideration of the corrosion period on the extreme value statistic analysis by the data of maximum depth of corrosion and on random variable was studied.

• The korean journal of orthodontics
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• v.25 no.3 s.50
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• pp.341-353
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• 1995

Previous study had shown the diversities in the propriety for optimal bond strength on the concentration of the etchant. The aim of present study in vitro was to evaluate and compare the shear bond strength of orthodontic brackets to enamel and to measure the depth of etch on the phosphoric acid concentrations. A hundred and seventy six extracted bovine lower centrals were ground to yield flat surfaces and etched by the concentration $0%,\;5%,\;10%,\;20%,\;30%,\;40%,\;50%,\;60%,\;70%,\;80%\;and\;85\%$ of phosphoric acid respectively during 60 seconds. The shear bond strength of orthodontic brackets, the depth of etch and surface roughness of the enamel were measured, and scanning electron microscopic observations on the etched enamel surfaces were carried out. The data obtained from the very experiments were processed and statistically analyzed and evaluated. The gradual increase in the depth of etch to enamel as the accretion of the concentration of the phosphoric acid upto $40-50\%$ and decline henceforth were manifested. The surface roughness showed no correlation with the depth of etch, yet moderate correlation with the shear bond strength of brackets. Scanning electron microscopic investigation revealed that morphological patterns of the etched enamel surfaces for $5\%\;to\;40\%$ of concentrations were even and homogenous, and those for $50\%$ as well as $60\%$ exhibited the overetched and unhomogenous. The shear bond strengths kom $10\%\;to\;60\%$ of concentration showed no statistically significant differences. It was suggested that the shear bond strengths at $5\%\;and\;70\%$ were sufficient to tolerate the force levels of the ordinary orthodontic treatment notwithstanding to be significantly lower than those from $10\%\;to\;60\%$ phosphoric acid solution.

• Magazine of the Korea Concrete Institute
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• v.4 no.2
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• pp.75-81
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• 1992

염분을 함유한 철근콘크리트중의 철근부식에 관한 2년 촉진시험으로부터 콘크리트표면에서 측정한 자연전위값과 실제의 철근 부식상황과를 비교한 결과 철근의 수식상황을 자연전위법을 이용하여 비파괴적으로 진단하는 방법이 유효함을 알았다. 포화칼로멜전극을 사용했을 경우 -300mV이하이면 부식이 발생하였으며 -200mV이상이면 부식이 발생하지 않았다. 또한 부시공시체에 대한 휨강도시험도 행하였으며 중성화에 대한 검토로 행하였다.

• The korean journal of orthodontics
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• v.26 no.5 s.58
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• pp.497-507
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• 1996

The aim of present study in vitro was to evaluate and compare the effects of different washing times of enamels etched with low phosphoric acid solution which makes unsoluble salts and etched but contaminated with saliva on shear bond strength of an orthodontic adhesive to enamel, and to observe the washing effect on the etched enamel surface by scanning electron microscope. All brackets were bonded with Mono-$Lok2^{TM)}$) on the labial surface of extracted human bicuspids after etching with $20w/w\%\;and\;37w/w$ and phosphoric acid solution for 60seconds and then washing for 0,5,10 and 20seconds respectedly. After etching with $37w/w\%$ phosphoric acid solution and contaminating with saliva for 30seconds and then washing for 0,5,20 and 30seconds and re-etching for 10seconds. After 24hours passed in the $37^{\circ}C$ water bath, the shear bond strengths were measured on Universal Test Machine. The data were evaluated and tested by ANOVA and Duncan's multiple range test, and those results were as follows. 1. There was no significant differences between (p>0.05) shear bond strength of bonded brackets with 5, 10, 20seconds washing etched enamel using $37{\%}w/w{\%}$ phosphoric acid solution. 2. The shear bond strength of bonded brackets with $20w/w\%$ phosphoric acid and then washing for 5seconds showed bonded strength durable to occlusal force but its coefficiency score was high and etched surface was not cleaned completely and therefore it was assumed that its clinical application is not applicable. 3. There was no significant differences between (p>0.05) shear bond strengths of bonded brckets with washing for 5seconds etched enamel using $37w/w\%$ phosphoric acid solution and 10,20 seconds washing etched enamel using $20w/w\%$ phosphoric acid solution. 4. The shear bond strength of washing for 5seconds etched enamel which was contaminated with saliva showed sufficient bonded strength durable to occlusal force but its coefficiency score was high and therefore its clinical application was not applicable. 5. After etching, the sample contaminated with saliva showed the sufficient shear bond strength even washing 20seconds without re-etching.

• The korean journal of orthodontics
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• v.40 no.2
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• pp.87-94
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• 2010

Objective: Many studies have carried out research on comparisons between laser etching and conventional etching systems to investigate methods of reinforcing shear bond strength. The purposes of this study were to assess the efficiency of bonding with erbium, chromium doped: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser etching combined with the conventional etching technique. Methods: Sixty-four sound premolars, extracted for orthodontic purposes, were randomly divided into 4 groups and treated in the following manner. First group, conventional etching of 37% phosphoric acid for 15 seconds (control); second group, 1.5 W laser etching for 10 seconds followed by conventional etching; third group, conventional etching followed by 1.5 W laser etching; fourth group, 1.5 W laser etching for 15 seconds only. We assessed the shear bond strength, the surface characteristics, and the adhesive remnant index scores between all groups. Results: Experimental groups showed higher shear bond strength than the control group. But no statistically significant differences were found between the second and third groups. Adhesive remnant scores were compared with the Kruskal-Wallis test, and no statistically significant differences were found between all groups. Conclusions: To obtain maximum shear bonding strength, a combined technique of Er,Cr:YSGG and 37% phosphoric acid is useful even though it may be inconvenient.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1029_1030
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• 2009

본 논문에서는 빔 에너지를 이용하여 내 마모 및 내 부식성을 갖는 철망을 가공하여, 빔 에너지 조사 전과 후의 SEM 사진과 인장강도를 측정하여 비교, 분석 하였다. 전자빔으로 표면을 개질하기 전보다 후의 표면이 더 치밀해짐을 SEM사진을 통하여 볼 수 있었고, 인장강도를 측정 하여 개질 전과 후를 비교 하였는데, 인장강도와 관련된 탄성계수가 더 크게 나타나 전자빔 조사에 의한 샘플이 긴 수명을 갖는 요인이 분석되었다.