• Title/Summary/Keyword: 부식평가

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The Utility of Phased Array Ultrasonic Testing(PAUT) for Corrosion Evaluation of Water Supply Steel Pipes (상수도 강관의 부식 평가에 대한 위상배열초음파(PAUT)의 활용)

  • Sang Hyeok Son;Chang Gun Shin;Jea Yeon Jeong;Jong Sik Kim
    • Proceedings of the Korea Water Resources Association Conference
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    • 2023.05a
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    • pp.490-490
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    • 2023
  • 위상배열초음파검사(PAUT)는 기존 초음파검사에서 획득할 수 있었던 A-scan의 결과와 달리, 관로 내부로 진입하지 않고도 부식에 의한 강관 손상 정도를 정량적인 시각적 데이터로 파악할 수 있는 검사 기술이다. 관내부 직접조사가 가능한 상수도 강관을 대상으로 직접조사와 PAUT를 비교한 결과, PAUT는 높은 정확도와 신뢰성을 보여주었다. 또한, 강관 내부의 부식검사에서는 PAUT를 적용함으로써 관체의 부식 면적, 부식 최대 깊이, 부식 위치를 넓은 범위에서 신뢰성 높은 검사 및 결과 도출이 가능하였다. 이러한 결과는 PAUT 기술이 강재 구조물의 다양한 부식 문제를 신속하게 파악하고 해결하는 데 기여할 수 있음을 의미한다. 따라서, 본 검사 기법은 상수도 관로의 강재 진단 및 점검에 있어 높은 신뢰성 및 효율성을 보여 주는 진단기법으로써 다양한 강재 시설물의 평가에 활용성이 클 것으로 판단된다. 이에 따라 PAUT는 상수도 시설물뿐만 아니라 다양한 시설물에서도 높은 활용 가능성을 가질 것으로 예상된다.

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고연소도 핵연료 피복관 개발 연구

  • 정용환;김창호;김경호;김성호;백종혁;김영석;국일현
    • Proceedings of the Korean Nuclear Society Conference
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    • 1996.05c
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    • pp.259-264
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    • 1996
  • 상용 Zircaloy-4보다 성능이 우수한 고연소도용 Zr 신합금을 개발하는 것을 목표로 외국에서 개발중인 12종의 신합금 피복관에 대한 특성평가, 부식기구 규명 연구, 국내에서 제조된 Zr 신합금의 특성평가를 실시하였다. 외국 피복관의 부식특성 평가로 부터 Sn을 0.6-1.0 wt.% 첨가하고 Nb을 0.4 wt.% 첨가하는 것이 내식성 관점에서 바람직함을 알 수 있었다. 여러 가지 LiOH용액에서의 부식기구 연구를 통해 수소화물이 부식가속의 원인임을 알 수 있었으며 수소화물 형성을 억제하는데는 Nb첨가가 효과적인 것으로 나타났다. 이와 같은 연구결과를 토대로 신합금의 개발방안을 수립하였으며 예비적으로 합금을 설계. 제조하여 특성시험을 실시한 결과, Zr-Sn-Nb-FeCr 합금이 우수한 내식성을 보이며 Fe, Mo는 강도 증가 효과가 큰 것으로 나타났다. 이러한 연구결과를 종합적으로 평가하여 신합금을 설계하고 노외성능 평가를 통해서 신합금을 선정한후, 단계적으로 하나로를 이용한 노내성능 평가를 실시할 예정이다.

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The Use of Galvanostatic Pulse Transient Techniques for Assessing of Corrosion Rate of Reinforcing steel in Concrete (정전류 펄스법을 이용한 콘크리트 내 보강철근의 부식 연구)

  • So, Hyoung-Seok
    • Journal of the Korea Concrete Institute
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    • v.19 no.6
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    • pp.785-793
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    • 2007
  • An electrochemical transient response technique was used to study the corrosion of reinforcing steel bar in the concrete. Analysis of the transient electrochemical potential response in a corrosion interface to an applied current has enabled the separate components that make up the measured transient response to be isolated. These components display a range of resistances and capacitances, dependent on the corrosion conditions of the reinforcing steel, which may be attributed to the corrosion process, to effects within the concrete cover or to film effects on the surface of the concrete. In this technique, the corrosion rate was evaluated by summing all of the resistances in the separate components to obtain an aggregated corrosion resistance. However, it is possible that not all resistances identified are associated with the corrosion process. The results obtained show that the corrosion rates are significant dependent on the assignment of the separate components to either corrosion or to other processes. The assignment of resistive components associated with the corrosion rate can be clearly identified by taking a series of the transient measurement at different lateral distances from the corroding reinforcing steel. An inappropriate selection of measurement time however may result in an additional resistance, which is not associated with corrosion, being included or part of the resistance associated with corrosion being left out.

Corrosion Durability Evaluation of Uncoated Structural Steel Using Accelerated Exposure Tests (부식촉진실험을 이용한 강교용 무도장 강재의 부식내구성 평가)

  • Kim, In Tae;Itoh, Yoshito
    • Journal of Korean Society of Steel Construction
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    • v.19 no.1
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    • pp.79-86
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    • 2007
  • The corrosion durability of steel bridge coatings, such as organic and metallic coatings, is often evaluated by field exposure tests, but such tests take from several years to decades to complete. As a potential method for fast corrosion testing, accelerated exposure tests were considered in this study. The S6-cycle accelerated exposure test, specified in the Japanese Industrial Standards (JIS K5621), was carried out on uncoated structural steels for 30, 60, 90, 120 and 150 days, and the resultant weight loss was determined. The weight loss was compared with that obtained from previous field exposure tests, and acceleration factors of the S6-cycle test to field exposure test sites were determined. The application of the S6-cycle accelerated exposure tests to field environments was presented based on the acceleration factor and the amount of flying salt.

Evaluation of Load Capacity Reduction in RC Beam with Corroded FRP Hybrid Bar and Steel (철근부식을 고려한 FRP Hybrid Bar 및 일반 철근을 가진 RC 보의 내력저하 평가)

  • Oh, Kyung-Suk;Moon, Jin-Man;Park, Ki-Tae;Kwon, Seung-Jun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.20 no.2
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    • pp.10-17
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    • 2016
  • Steel corrosion is a very significant problem both to durability and structural safety since reinforcement has to support loads in tensile region in RC(Reinforced Concrete) member. In the paper, newly invented FRP Hybrid Bar and normal steel are embedded in RC beam member, and ICM (Impressed Current Method) is adopted for corrosion acceleration. Utilizing the previous theory of Faraday's Law, corrosion amount is calculated and flexural tests are performed for RC beam with FRP Hybrid Bar and steel, respectively. Corrosion amount level of 4.9~7.8% is measured in normal RC member and the related reduction of flexural capacity is measured to be -25.4~-50.8%, however there are no significant reduction of flexural capacity and corrosion initiation in RC samples with FRP Hybrid Bar due to high resistance of epoxy-coated steel to corrosion initiation. In the accelerated corrosion test, excellent performance of anti-corrosion and bonding with concrete are evaluated but durability evaluation through long-term submerged test is required for actual utilization.

An Experimental Study on the Evaluation of Residual Tensile Load-carrying Capacity of Corroded Steel Plates of Temporary Structure (가시설 부식 강재의 잔존 인장 내하성능 평가에 관한 실험적 연구)

  • Kim, In-Tae;Chang, Hong-Ju;Cheung, Ji-Young
    • Journal of Korean Society of Steel Construction
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    • v.22 no.5
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    • pp.399-409
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    • 2010
  • Steel structures are threatened to reduce load-carrying capacity as the cross section is decreased by corrosion. However, there has been no method in definitely evaluating residual load-carrying capacity and the effect of corrosion to the load-carrying capacity of steel. This study evaluated tensile residual load-carrying capacity of corroded steel plates by using tensile tests of specimens, which were selected from the web of temporary structure's main beam. After the surface shapes were measured and tensile tests were examined, the rust of 21 corroded specimens was, first of all, removed using a chemical method. From the tensile test result, which of reference specimens that was picked off at the flange of the same main 13-mm-thick beam and corroded specimens were based, surface geometry and correlation with the reduction of corroded thickness and strain, yield strength or tensile strength was established as constant numbers. Effective thickness of corroded steel with irregular cross sections could be calculated using average residual thickness and standard deviation. The irregular cross sections could be the evaluated tensile strength that is equalized to non-corroded uniform steel's regardless of corrosion. Also, reasonable measuring intervals of residual thickness could be proposed by using this result to apply for executive work.

Correlation of Surface Chloride and Corrosion Amount for Steel Member Exposed in Marine Environment (해양환경에 노출된 강부재의 표면염분과 부식량 상관관계)

  • Min-Gyun Ha;Chang-Jae Heo;Hoon Yoo;Jin-Hee Ahn
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.27 no.4
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    • pp.45-53
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    • 2023
  • In this study, to analyze the correlation of surface chloride and corrosion amount level according to the installation location of steel members exposed to the marine environment, the surface chloride and mean corrosion depth were evaluated by member units for box girder members of the offshore steel bridge and box specimens. The surface chloride was measured monthly using the Bresle method for one year. The corrosion amount was evaluated by converting the weight loss due to corrosion products generated in the monitoring steel plate into mean corrosion depth. As a measurement result of the surface chloride and corrosion amount, relative differences in surface chloride and mean corrosion depth were appeared depending on the shape or installation location of the steel members. Moreover, even if members of the same shape were installed in the same bridge, it was confirmed that the corrosion amount was increased locally and rapidly. The tendency of corrosion amount depending on the surface chloride was evaluated to analyze the correlation between surface chloride and corrosion amount, and the relation equations that can asseses the corrosion amount depending on the surface chloride were analyzed. From the results of the correlation between surface chloride and corrosion amount, it was found that the corrosion amount of the steel member affected by the surface chloride was varied up to about 1.15 times depending on the structural detail.

Radiometric Scanning System for the Inspection of the Pipeline (방사선을 이용한 배관 검사 시스템 제작)

  • Kim, Yong-Kyun;Hong, Seok-Boong;Chung, Chong-Eun;Park, Se-Hwan;Lee, Woo-Gyo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.05b
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    • pp.164-168
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    • 2003
  • Digital 방사선투과검사 시스템인 1차원 Radiometric scanning system을 개발하여 부식 및 침적물이 있는 배관의 두께평가에 적용하였다. 단일 방사성 동위원소에서 나오는 방사선을 선현으로 접속하여 시험체를 투과시킨 방사선을 BGO 검출기를 사용하여 측정하는 single source - single detector alignment system과 제어 프로그램을 개발하였다. 개발된 시스템의 성능을 GEANT4 프로그램을 사용하여 예측하였다. 그리고, 인공결함을 제작하여 넣은 시편과 두께 변화를 준 시편에 적용하여 실제 성능을 평가하였다. 방사성 동위원소를 이용하여 배관의 부식과 침적물에 의한 두께 변화에 대하여 실시간으로 필름을 사용하지 않고 평가할 수 있음을 확인하였다.

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Effect of Concrete Water-Binder Ratio and Mineral Admixture on Corrosion Estimation by Electro-Chemical Method (콘크리트 물-결합재비 및 광물질 혼화재가 전기-화학적 기법에 의한 부식 평가에 미치는 영향)

  • Yang, Eun-Ik;Choi, Yoon-Suk;Han, Sang-Hun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.14 no.2
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    • pp.75-81
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    • 2010
  • In this study, when concrete properties are changed by concrete mix proportions or blending of admixtures, the characteristics of electro-chemical method for corrosion assessment of the embedded steel are compared and its causes are analyzed. According to the results, when the ratio of corroding area was less than 10%, the half-cell method was affected by concrete properties. In the case of specimen blended admixtures, it is possible to assess the high-corroded steel qualitatively using the half-cell method. For the polarization resistance method, though the corroding area was less than 10%, it has not affected by concrete properties. However, in case of specimen blended admixtures, the corrosion level of steel was underestimated than OPC specimens having a similar corroding area.

Safety Assessment of Corrosion-damaged Steel Structure using Imprecise Reliability (불확실 신뢰도 기법을 이용한 부식된 강구조물의 안전도평가)

  • Choi, Hyun Ho;Cho, Hyo Nam;Seo, Jong Won;Sun, Jong Wan
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.2A
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    • pp.293-300
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    • 2006
  • There is a high degree of uncertainty in measurements of the thickness or the loss of thickness of corroded elements. Generally the thickness of corroded elements varies from one location of the element to another depending on the degree of corrosion, which makes the safety assessment difficult. Therefore, a procedure for safety assessment of corrosion- damaged steel structures using an imprecise reliability is proposed in this paper. The proposed safety assessment procedure using the imprecise reliability was also applied to a cable-stayed bridge in Korea to demonstrate its effectiveness and applicability. Since there is a large variation in measurements of the thickness of corroded elements, the thickness of corroded elements was considered as the imprecise element. This variation was found to be directly related to the degree of corrosion. Therefore, the variation increases as the degree of corrosion increases. Based on the comparative observations between the conventional reliability and the imprecise reliability, it is suggested that the imprecise reliability analysis derived based on the subjective or statistical judgment of conditional independence could be successfully utilized for the risk or safety assessment of corrosion-damaged structures.