• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.109-109
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• 2018

Cr-Mo 합금강은 고온 환경 하에서 높은 크리이프 강도와 우수한 내식성 때문에 발전설비, 석유 화학, 그리고 해양산업과 같은 여러 산업분야에서 널리 사용되고 있다. 특히, Cr-Mo 강의 내식성은 합금 내 Cr 함량에 크게 의존한다. 이는 고온에서 Cr과 O가 화학적 반응을 일으킴에 따라 보호성의 Cr 산화스케일을 형성하기 때문이다. 그러나 화석연료를 사용하는 발전설비의 경우, $SO_2$가 포함된 강한 부식성의 연소 가스가 배출되며, 이에 노출된 금속의 표면에서는 산화와 황화가 동시에 발생한다. 황화스케일은 산화스케일에 비해 매우 빠르게 성장하며, 그 특성이 매우 취약하기 때문에 황화 환경에서 금속의 내식성 및 기계적 물성치는 보다 크게 저하된다. 따라서 본 연구에서는 화력 발전소의 증기발생용 튜브 재료인 9Cr-1MoVNb 강을 선정하였으며, $SO_2$ 가스 환경 하에서의 부식 및 기계적 물성치 저하 특성을 평가하고자 하였다. 본 연구에서 사용된 9Cr-1MoVNb강의 화학 성분 조성은 0.1 C, 0.38 Si, 0.46 Mn, 0.25 Ni, 8.38 Cr, 0.93 Mo, 0.18 V, 0.09 Nb, 그리고 나머지는 Fe이다. 부식시험은 가공된 미소시험편과 인장시험편을 전기열처리로에 장입한 후, $650^{\circ}C$에서 $N_2+O_2+O_2+SO_2$ 조성의 가스를 분당 50 CC로 흘려주었다. 제작된 시험편에 대한 부식거동은 무게 증가량, optical microscope, scanning electron microsope, 그리고 energy dispersive x-ray spectrum을 통해 평가하였다. 그리고 기계적 물성치 평가를 위한 인장시험은 분당 2mm 변위제어를 통해 실시하였다. 그 결과, 9Cr-1MoVNb 강은 $SO_2$ 가스 환경 하에서 비 보호적인 Fe-풍부상의 산화 스케일층이 두껍게 형성됨에 따라 열악한 내식성을 나타냈다. 그에 따라 기계적 물성치는 저하되는 경향을 나타내었다.

• Elastomers and Composites
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• v.40 no.1
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• pp.59-65
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• 2005

Zinc methacrylate(ZMA) was incorporated into ethylene-propylene diene rubber(EPDM) by direct mixing of the metal salt with the rubber or was in-situ prepared in the rubber matrix through neutralization reaction of zinc oxide(ZnO) and methacrylic acid(MAA). Tensile and tear tests showed that ZMA had a great reinforcing effect for the EPDM. It was also found that ZMA reinforced EPDM vulcanizates can retain their mechanical properties under thermo-oxidative aging. Moreover the incorporation of ZMA induces a substantial improvement in the adhesive strength of the EPDM onto aluminum substrate. The reinforcing effect and an enhancement in adhesion was greatly manifested when the ZMA is in-situ formed with an excess amount of ZnO. The extraordinary improvement in the properties is supposed to be related with the formation of ionic crosslink as well as the degree of dispersion or ZMA domain in the rubber matrix.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.2
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• pp.497-505
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• 2017

TDF (Tire derived fuel) Fly ash is an industrial by-product when scraped tire was used a fuel source at the power plant. TDF Fly ash has been classified as domestic waste at the workplace so far and has not been appropriately utilized. We conducted a fundamental physical property test of asphalt mixture to investigate the possibility of using TDF Fly ash as a mineral filler of asphalt mixture for exploring new usage strategies. TDF Fly ash meets KS F 3501 asphalt mixture mineral filler criteria. And the optimal asphalt binder amount was determined to be 4.5% by Marshall design. Mineral filler content was determined at 3% and analyzed by comparing using mineral filler as stone powder. The basic physical property test of the asphalt mixture was evaluated to the provision indicated in "Production and Construction Guidelines for Asphalt Mixture" published by the Ministry of Land, Infrastructure and Transport. In the test, Marshall stability test, dynamic immersion test, tensile strength ratio test, wheel tracking test were carried out. As a result of the experiment, Marshall stability and dynamic stability satisfied the standards, and confirmed the stability and Dynamic immersion and tensile strength ratio test that TDF Fly ash is more effective for scaling and moisture resistance than stone dust. Therefore, in this research, it is expected that multilateral utilization of TDF Fly ash, and a positive effect can be also expected.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.224-227
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• 2002

비행선 기낭을 개발하기 위한 막재 요구조건과 이를 만족하기 위한 막재(membrane)의 구성을 살펴보고, 실제 연구에 사용된 기낭재료의 조성과 소재 기본 물성시험 그리고 접착강도, 패치강도 등과 같은 설계개발시험을 수행한 결과 및 향후 계획을 소개한다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.88-88
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• 2004

내압을 받는 압력관의 파괴는 원주방향의 응력이 주된 요인이므로, 압력관의 안전성을 평가를 위해서는 원주방향의 인장특성을 아는 것이 필요하다. 소형 압력관의 인장특성을 평가할 때, 정확한 원주방향의 인장특성을 알기 위해서는 관으로 가공된 후의 재료로 시험해야 하지만, 부피의 제약으로 인하여 원주방향으로의 표준 인장시험편을 제작하지 못하므로 가공하기 전의 재료의 물성치를 사용하고 있다. 이를 개선하고자 원주방향의 인장특성을 평가하기 위한 방법의 하나로 링 시험법(ring test)이 있다.(중략)

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05d
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• pp.300-305
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• 1996

격납건물용 콘크리트는 그 배합이 변경될 때마다 장기거동 특성시험 (크립, 건조수축, 탄성계수, 포아슨비, 열팽창계수 등)을 수행하여 그 시험결과를 설계회사가 텐돈의 인장 작업전까지 검토하게 되어 있으나, 이 중 크립(Creep)시험은 특성상 장기간이 소요되는 관계로 적시에 시험결과를 제공할 수 없는 경우가 종종 발생한다. 본 연구에서는 이 경우 유사한 배합비를 가진 콘크리트와의 물성치 대비 및 크립 변형율의 예측을 통하여 실험치가 허용치 이내에 드는 가를 분석하므로써, 사용된 콘크리트의 크립거동에 대한 안정성을 검토하였다.

• Journal of the Korean Geosynthetics Society
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• v.18 no.4
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• pp.115-127
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• 2019

The low-flow grouting injection technique, the target construction method for this study, is a method of pouring mortar into the ground by non-emission replacement principle, which can be expected to increase the density of the ground, and, in some cases, be used as a base file using the strength of the high injection solids, along with low noise, low pollution, and high durability. To verify that the dynamic characteristics of the ground are improved by the low-flow injection technique, the test work was conducted on the site and physical tests were performed, and the quality of the improvement formed in the ground was verified through the indoor test on the core and core recovery rate was analyzed. The density logs test layer calculated the volume density of the ground layer by using the Compton scattering of gamma-rays, and the sonic logs was tested on the ground around the drill hole using a detector consisting of sonar and receiver devices inside the drill hole. As a result of the measurement of the change in physical properties (density and sonic logs) before and after grouting, both properties were basically increased after infusion of grout agent. However, the variation in density increase was greater than the increase in speed after grouting, and the ground density measurement method was thought to be effective in measuring the fill effect of the filler. Strength and core recovery rates were measured from specimens taken after the age of 28 days, and the results of the test results of the diffusion and strength test of the improved products were verified to satisfy the design criteria, thereby satisfying the seismic performance reinforcement.

• International Journal of Highway Engineering
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• v.6 no.3 s.21
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• pp.9-15
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• 2004

The cracking resistance of asphalt mixtures is generally evaluated by measuring a single parameter (i.e., Tensile strength, Stiffness). However, the use of a single parameter has been questioned in the evaluation of asphalt mixture cracking performance. The focus of this study was to clearly identify the key properties and characteristics associated with the cracking resistance of asphalt mixtures. Results of fracture, creep, and strength tests at multiple loading rates performed on the modified and unmodified mixtures showed that the mixture cracking resistance was primarily affected by the rate of micro-damage accumulation. This was reflected in the m-value, without affecting the fracture energy limit. It was also observed that the short loading time (elastic) stiffness alone could not differentiate the mixture cracking resistance of the mixtures. It was concluded that the key to characterize the cracking resistance of asphalt mixture is in the evaluation of the combined effects of creep and failure limits. It was also found that a residual dissipated energy parameter measured from Superpave IDT strength test gave the quick and useful way to distinguish the difference of cracking resistance of asphalt mixtures. Failure strain in the longer-term creep test appeared to be a useful parameter for evaluating the combined effects of creep and failure limits of asphalt mixtures.

• Journal of the KSME
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• v.49 no.5
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• pp.28-31
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• 2009

• Computational Structural Engineering
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• v.16 no.2
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• pp.62-70
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• 2003