• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 춘계학술대회 논문집
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• pp.421-426
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• 2005

In general, structural integrity of rolling stock structures should last more than 25 years. During the lifetime corrosive degradation occurs. For structural design and diagnosis, quantitative relationship between corrosive degradation and variation of mechanical properties such as tensile strength and fatigue strength is needed. In this study, first of all we established the atmospheric corrosion test procedure. At regular intervals using specimens of SM490A and SS400 on the atmospheric corrosion test bed, we carried out tensile and fatigue tests. The fatigue strength decreases as the atmospheric corrosion period increases. And we studied the effect of post-weld heat treatment on the tensile and fatigue behaviour.

• 동력기계공학회지
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• 제13권1호
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• pp.46-52
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• 2009

The steel impeller placed in a water pump has been studied with the aim to understand corrosion phenomena on the surface responsible for reducing the pumping efficiency of water inside cooling system. This preliminary experiment includes a period (over 5 months) observation with a powered microscope and weight measurements. The experiments are carried out at different conditions of water and mixtures of water and coolants, based on the water contents of 25%, 50%, 75%, and 100% water (pure tap water). From the visual results of microscopy, most of the steel surface is fitted and clear rusty or corrosion phenomena are noticeable as time goes. In addition, the weight loss of the sample specimen submerged in the water is linearly increased, whereas those in the mixtures of water initially be constant and then gain weight linearly.

• 전기학회논문지
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• 제56권2호
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• pp.338-342
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• 2007

The increase of activated carbon contents in fly ashes accelerate the corrosion of steel embedded in ordinary portland cement(OPC) mortar. Cement losses its identity of colour when the % of carbon is increased. More than 60[%] area was rusted when carbon content is increased beyond 8[%] for the exposure period of one year. Comparable corrosion rate with OPC was obtained up to 6[%] carbon level only. The tolerable limit of replacement for various admixed carbon system under aggressive alternate wetting and drying condition with 3[%] NaCl was found to be 6 to 8[%].

• International Journal of Precision Engineering and Manufacturing
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• 제4권6호
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• pp.12-19
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• 2003

This paper presents the effect of boundary conditions in various failure pressure models published for the estimation of failure pressure. Furthermore, this approach is extended to the failure prediction with the aid of a failure probability model. The first order Taylor series expansion of the limit state function is used in order to estimate the probability of failure associated with each corrosion defect in buried pipelines for long exposure period with unit of years. A failure probability model based on the von-Mises failure criterion is adapted. The log-normal and standard normal probability functions for varying random variables are adapted. The effects of random variables such as defect depth, pipe diameter, defect length, fluid pressure, corrosion rate, material yield stress, material ultimate tensile strength and pipe thickness on the failure probability of the buried pipelines are systematically investigated for the corrosion pipeline by using an adapted failure probability model and varying failure pressure model.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.15-30
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• 2005

The increasing amount of structures presenting distress due to reinforcement corrosion is urging the establishment of more accurate calculation methods for the service life of concrete structures. In the present paper, a summary of the different approaches is presented that are able to calculate the expected life of new structures, in certain aggressive environments or the residual life of already corroding structures. The methods for the initiation period are based on the proper calculation of the carbonation front or chloride penetration and on the steel corrosion rate. The methods for the residual load-bearing capacity calculations are based in the use of ' indicators ' or in the evaluation of the reduced section and a structural recalculation.

• Corrosion Science and Technology
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• 제5권3호
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• pp.106-111
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• 2006

Painting has protected metallic stack but the paint films may be degraded and corrosion problem can be arisen. To protect the painted metal stack, cathodic protection can be applied. If cathodic protection is applied to bare metal, only small area may be protected. However, if cathodic protection is applied to painted metal surface, large area can be protected and the lifetime of paint films can be extended. High corrosion resistant alloys were corroded at a Flue Gas Desulfurization (FGD) facility of power plant within a short period and thus cathodic protection can be used to protect these metals. On the base of computer simulation, if cathodic protection is applied to bare metal in a FGD environment, it was estimated that applied current could almost be spent to protect area near the anode. However, if cathodic protection is applied to high resistant-coated metal, the much larger area from the anode could be effectively protected.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2005년도 학술발표대회 논문집
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• pp.349-355
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• 2005

The bolts used for the electronic parts of a car a is the important parts which carry out an electric and physical performance. At the time of storage, transportation and use, Corrosion occurs in bolts under the influence of environmental factor. During the period exported especially overseas the chemical corrosion by the chlorine ion contained in the atmosphere occurs frequency. Then, The failure mechanism over corrosion is investigated and we consider to the design procedure of a environmental examination. We are going to select the proper plating thickness of bolts through a salt spray test, for investigating the corrosion resistance of bolts.

• Corrosion Science and Technology
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• 제9권2호
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• pp.57-66
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• 2010

Since nuclear power plants are being operated under high temperature and high pressure, on-line monitoring technique to detect corrosion could be more effective than off-line method in shut-off period. In this operating condition, electrochemical noise method may be suitable to monitor the corrosion. This paper aims the analysis on the relation between the cracking and electrochemical noise signal of Alloy 600 under U-bending. When electrochemical noise monitoring technique was used during SCC test, it was judge to be obvious that if cracks generate, its generation can be detected by electrochemical current noise. Cracking-related noise was defined as the noise showing 5~10 times greater than the average value of background noise bands. On the base of crack noise, crack initiation time was determined. From SCC test and electrochemical noise monitoring in $25^{\circ}C$, 0.1 M $Na_2S_4O_6$ solution (Reverse U-Bended Alloy 600 SE+), average crack initiation time was obtained as 9,046 seconds and from its initiation time, it could be defined that net crack propagation rate is the crack length divided by ${\Delta}T$(= total test period - crack initiation time). Therefore, average net crack propagation rate was obtained to be $1.18{\times}10^{-9}\;m/s$.

• Corrosion Science and Technology
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• 제15권5호
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• pp.245-252
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• 2016

The pipelines and equipments are degraded by flow-accelerated corrosion (FAC), and a large-scale test facility was constructed for simulate the FAC phenomena in secondary coolant environment of PWR type nuclear power plants. Using this facility, FAC test was performed on weld pipe (carbon steel and low alloy steel) at the conditions of high velocity flow (> 10 m/s). Wall thickness was measured by high temperature ultrasonic monitoring systems (four-channel buffer rod type and waveguide type) during test period and room temperature manual ultrasonic method before and after test period. This work deals with the complex effects of flow velocity on the wall thinning in weld pipe and the test results showed that the higher flow velocity induced different increasement of wall thinning rate for the carbon steel and low alloy steel pipe.

• 한국건설순환자원학회논문집
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• 제12권3호
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• pp.239-245
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• 2024

PS 텐던의 경우 높은 인장응력을 받고 있으며, 피복두께가 RC에 비해 상대적으로 작으므로, 부식에 관한 엄격한 기준을 가지고 있다. 본 연구에서는 7연선 텐던의 소선 위치에 따른 부식거동을 평가하기 위해 3 수준의 염화물 농도(0.0 mol/l, 0.125 mol/l, 0.25 mol/l)를 고려하였다. 촉진부식조건과 부식량 측정을 위해 텐던을 부분 포화상태의 모래에 매립하였으며, 표면으로부터 HCP(Half Cell Potential)를 평가하였다. 28주의 부식모니터링 기간 동안 2주 간격으로 HCP를 측정하고 16주와 28주에 텐던의 부식질량을 측정하였다. 측정결과 소선이 상부에서 하부로 위치할수록 HCP값이 증가하였고, 0.25 mol/l 인 경우 상부에 비하여 하부에서는 HCP이 최대 5.92 %가 증가하였다. 소선의 위치가 낮을수록 포화도가 크므로 부식량이 증가하였으며, HCP도 하부에서 크게 측정되었다. 또한 부식질량률과 염화물 농도와의 관계가 회귀분석을 통하여 정량적으로 도출되었다.