• Tribology and Lubricants
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• 제24권3호
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• pp.129-132
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• 2008

Fuel cladding tubes in nuclear fuel assembly are held up by supporting grids because the tubes are long and slender. Fluid flows of high-pressure and high-temperature in the tubes cause oscillating motions between tubes and supports. This is called as FIV (flow induced vibration), which causes fretting wear in contact parts of tube and support. The fretting wear of tube and support can threaten the safety of nuclear power plant. Therefore, a research about the fretting wear characteristics of tube-support is required. The fretting wear tests were performed with supporting grids and cladding tubes, especially after corrosion treatment on tubes, in water. The tests were done using various applied loads with fixed amplitude. From the results of fretting tests, the wear amounts of tube materials can be predictable by obtaining the wear coefficient using the work rate model. Due to stick phenomena the wear depth was changed as increasing load and temperature. The maximum wear depth was decreased as increasing the water temperatures. At high temperatures there are the regions of some severe adhesion due to stick phenomena.

• International Journal of Automotive Technology
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• 제8권3호
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• pp.343-349
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• 2007

One of the useful technologies for light-weightening of components required in the automobile and machine industry is to use high strength materials. To improve material properties, the carbonizing treatment, nitrifying treatment, and shot-peening method are representatively applied. However, the shot-peening method is generally used to remove surface defect on steel and to improve the fatigue strength of the surface. Benefits of shot-peening are increasing resistance against fatigue, stress corrosion cracking, fretting, galling, erosion and closing of pores. In this paper, the effect of shot-peening on the corrosion of SUP-9 steel immersed in a 3.5% NaCl solution and corrosion characteristics from heat treatment during the shot peening process has been investigated. The immersion test was performed on four kinds of specimens. Corrosion potential, the polarization curve, residual stress etc. Were analyzed from the experimental results.

• 대한기계학회논문집A
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• 제35권8호
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• pp.951-956
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• 2011

원자력 발전설비의 증기발생기용 세관 재료로 인코넬 합금이 사용되고 있다. 인코넬 합금은 고니켈과 크롬의 합금으로 고온에서 내부식성이 뛰어난 특성을 가지고 있다. 본 연구에서는 인코넬 600 과 690 합금에 대해 실제 원전의 운전온도, 즉 $320^{\circ}C$가 프레팅 피로 거동에 미치는 영향에 대해 연구해보았다. 그 결과 $320^{\circ}C$에서의 단순 피로한도와 프레팅 피로한도가 상온에서의 단순 및 프레팅 피로한도에 비해 다소 저하하는 것을 알 수 있었다. 아울러 하중 반복회수와 마찰력의 변화 특성도 얻었다. 또한 파단면을 전자현미경으로 관찰하여 프레팅 피로기구도 검토해 보았다. 이와 같은 결과는 실제 운전온도에서 프레팅을 받는 증기발생기의 구조건전성 평가에 활용 가능할 것으로 생각된다.

• 한국자동차공학회논문집
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• 제13권1호
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• pp.159-165
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• 2005

Shot peening can be defined as the process of work hardening of the surface of components by means of propelled stream of spherical shot. Benefits due to shot peening are increase in resistance to fatigue, stress corrosion cracking, fretting, galling, erosion and closing of pores. In this study, the influence of shot peening on the corrosion was investigated on spring steel immersed in $3.5\%\;NaCl$. The immersion test was performed on the two kinds of specimens. Corrosion potential, polarization curve, residual stress and etc. were investigated from experimental results. From test results, the effect of shot peening on the corrosion was evaluated. The important results of the experimental study on the effects of shot peened spring steels on the environment corrosion are as follows; In case of corrosion potential, shot peened specimen shows more activated negative direction as compared with parent metal. Surface of specimen, which is treated with the shot peened, is placed as more activated state against inner base metal. It can cause the anti-corrosion effect on the base metal.

• 대한기계학회논문집A
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• 제29권7호
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• pp.930-937
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• 2005

One of the useful technology for light-weightening of components required in the automobile and machine industry is to use of high strength materials. To improve material properties, carbonizing treatment, nitrifying treatment, and shot-peening method are representatively applied, However, the shot-peening method is generally used to remove the surface defect of steel and to improve the fatigue strength on surface. Benefits by shot peening are to make increase resistance against fatigue, stress corrosion cracking, fretting, galling, erosion and closing of pores. In this paper, investigated the effect of shot peening on the corrosion of SUP-9 steel immersed in $3.5\%$ NaCl solution and corrosion characteristics by the heat treatment during shot peening process. The immersion test was performed on the four kinds of specimens. Corrosion potential, polarization curve, residual stress and etc. were investigated from the experimental results.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.325-330
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• 2004

Recently, the request for the high strength of material is more and more increased in the area of industrial environment and machinery. To accomplish the high strength of materials, carbonizing treatment, nitrifying treatment, shot-peening method are representatively applied, however, shot-peening method is generally used among the surface processes. Shot peening is a cold working process used to impact Compressive residual stressed in the exposed surface layers. Benefits due to shot peening are increase in resistance to fatigue, stress corrosion cracking, fretting, galling, erosion and closing of pores. In this study, the influence of shot peening on the corrosion was investigated on spring steel immersed in 3.5% NaCl. The immersion test as performed on the two kinds of specimens. Corrsion potential, polarization curve, residual stress and etc, were investigated from experiment results. From test result the effect of shot peening on the corrosion was evaluated. The important results of the experimental study on the effects of shot peened on the environment corrosion of spring steels are as follows; In case of corrosion potential, shot peened specimen shows more activated negative direction as compared with parent mental. Surface of specimen, which is treated with the shot peened is placed as more activated state against inner base metal. It can cause t도 anti-corrosion effect on the base metal.

• 한국산업융합학회 논문집
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• 제7권4호
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• pp.399-405
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• 2004

Currently, the use of carbon steel in a high temperature environment, such atomic reactor, increases. Test piece was heated in electric furnace and the prescribed temperature was controlled within ${\pm}1^{\circ}C$. Debris that falls apart from cracked section due to friction is accumulated inside. Then, as it causes fretting corrosion (formation of oxide layer), it contributes to crack closure.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.2047-2052
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• 2004

Inconel-600 alloy has been used as steam generator tube material for current pressurized water reactors (PWRs). The long-term operation of steam generators showed that the use of this material induced localized corrosion damages and increased tube wear of steam generator. To protect these problems, steam generator tube material is being changed to Inconel-690 alloy. Based on the current trend, we have chosen Inconel 690 as the Advanced Power Reactor 1400 (APR1400) steam generator(SG) tube material and performed the design optimization of preventive measure against tube fretting wear for the APR1400 steam generator. In this paper, we examined the technical consideration in this modification : the selection of material, wear characteristics, effect of the Egg-crate Flow Distribution Plate installation, and effect analysis of vertical strip installation.

• Corrosion Science and Technology
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• 제8권3호
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• pp.126-131
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• 2009

The interaction between wear and corrosion can significantly increase total material losses in water chemistry environment. The corrosive wear tests of a PWR steam generator tube material (Alloy 690) against the anti vibration bar material (409 SS) were performed at room temperature. The tests were performed in alkaline water chemistry conditions. NaOH solution was selected for test condition to investigate the corrosive wear effect of steam generator tube material in alkaline pH condition without other factors. The flow induced vibration can caused tube damage and the corrosion can be occurred by water chemistry. The test results showed that, in the alkaline solution at pH 13.9, the corrosion current density was increased about ten times than that in the distilled water. And wear rate at pH 13.9 was increased about ten times from that at neutral condition. However, the wear rate was decreased with time. The decrease would be attributed to the change in roughness of specimen or sub-layer of the worn surface with time. From microstructure observation, severe abrasive shape and several wear debris were found. From those results, it could infer that the oxide film on Alloy 690 changed to easily breakable one in the alkaline water, and then abrasion with corrosion became the main wear mechanism.

• 한국산업안전학회:학술대회논문집
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• 한국안전학회 2000년도 추계 학술논문발표회 논문집
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• pp.257-262
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• 2000

원전을 가동함에 따라 전열관에서는 SCC(stress corrosion cracking), 프레팅(fretting) 등과 같은 다양한 종류의 결함이 발생된다. 이러한 결함이 발생된 전열관에 대해서는 건정성 평가를 수행하여 계속 가동을 수행하던가, 전열관 막음(plugging) 또는 재생보수(sleeve) 등의 보수 작업을 수행하게 된다. 현행 전열관의 구조 건정성 확보를 위한 방안 중의 하나로 결함의 종류, 위치 등에 관계없이 모든 결함에 대하여 40% 관두께 기준을 적용하고 있다［1］. 그러나 현재 적용되고 있는 40% 관두께 보수기준은 전열관의 파열사고 가능성을 완벽하게 차단하지 못하면서도 과도하게 보수적인 측면이 있다.(중략)