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RISS 인기검색어
- 검색키워드
- 저자 : 임경수(Kyoung Soo Im) (검색결과 5 건)
- 무료
- 기관 내 무료
- 유료
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Zr-2.5Nb 압력관 크랙선단에서 수소화물의 응력해석
김강수(Kang Soo Kim),김영석(Young Suk Kim),정용무(Yong Moo Cheong),안상복(Sang Bok Ahn),임경수(Kyoung Soo Im) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.3
Delayed Hydride Cracking (DHC) tests are conducted by using CT specimens of Zr-2.5Nb at 250℃. The test data is inputed for the FEM model. The stresses of the hydride and Zr-2.5Nb elements near the crack tip of the FEM model are examined. Also, the plastic zone size and average stresses near the crack tip are calculated for checking the effects of the plastic constraint. The material behavior of the elements near a crack tip, the hydride expansion stress, the hydride fracture strength and the size of the plastic zone according to each K are found. Also, Stage Ⅰ and Stage Ⅱ of the unique DHC phenomenon can be explained through an analysis of the plastic constraint force in the plastic zone.
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김강수(Kang Soo Kim),김영석(Young Suk Kim),정용무(Yong Moo Cheong),안상복(Sang Bok Ahn),임경수(Kyoung Soo Im) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.8
The objective of this study is to suggest the new mechanism of DHC. At the stage Ⅰ of DHC, DHC velocity increase quickly and that is constant at the stage Ⅱ even if the stress intensity factor(K) increase. Also, the striation spacing on the fractured surface of DHC CT specimen is firstly wide and becomes gradually narrow according to increasing K value. Finally, that becomes constant at the stage Ⅱ. The new DHC model suggested can explain the above situation. To this end, CT specimen is modelled using FEM and the behavior of the elements near the crack tip is examined. Also, the direction of the principal stress, the maximum shear stress and the plastic zone size near the crack tip is calculated.
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Zr-2.5Nb 압력관에서의 Striation Spacing과 DHCV의 관계
최승준(Seung Jun Choi),안상복(Sang Bok Ahn),김성수(Sung Soo Kim),임경수(Kyoung Soo Im),김영석(Young Suk Kim) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.8
The objective of this study is to elucidate a relationship between striation spacing and DHCV in Zr-2.5Nb tubes. To this end, DHC tests were conducted at different temperatures ranging from 100 to 300 oC with 3 to 6 data set at each test conditions for data confidence. Hydrogen charging amount was determined with testing temperature, from 27 to 87 ppm. Before applying load, specimens were heated up in order to dissolve hydrogen into matrix, and cooled down to testing temperature. From the results, DHCV and striation spacing increased with increased testing temperature, leading to a apparent relation that striation spacing became larger with increased DHCV. However, through a normalization of DHCV by diffusivity and solubility of hydrogen, it is found that the DHCV decreased with increased striation spacing. This correlation of the striation spacing and the DHCV was confirm through DHC tests on irradiated Zr-2.5Nb tubes with higher yield strength demonstrating the higher DHCV with the smaller striation spacing.
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노치 형상 및 냉각속도에 따른 Zr-2.5Nb 압력관의 DHC거동
김상재,김영석,임경수,김성수,정용무 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.1
The objective of this study is to investigate the delayed hydride cracking (DHC) velocity and the incubation time for the water-quenched and furnace-cooled Zr-2.5Nb tube with the different radius of a notch tip. DHC tests were carried out at constant K_1 of 20 MPa√m and 250℃ on the cantilever beam (CB) specimens subjected to furnace cooling or water quenching after electrolytic charging with 57 or 72 ppm hydrogen, respectively. An acoustic emission sensor was attached to the CB specimens to detect the incubation time before the start of DHC. The shape of the notch tip changed from the fatigue crack to the dull crack with its radius ranging from 0.1 to 0.15 mm. The DHC incubation time increased remarkably with the increasing radius of the notch tip, which appeared more strikingly on the furnace-cooled CB specimens than on the water-quenched ones. However, both furnace-cooled and water-quenched CB specimens indicated little change in the DHC velocity with the radius of the notch tip unless their notch tip exceeded 0.125mm. These results demonstrate that the uncleation rate of hydrides at the notch tip determines the incubation time and the DHC velocity becomes constant after the concentration of hydrogen at the notch tip reaches the terminal solid solubility for dissolution (TSSD). This observation agrees well with Kim's DHC model. A difference in the incubation time and the DHC velocity between the furnace-cooled and water-quenched specimens is discussed in terms of the uncleation rate of hydrides at the notch tip and the hysteresis of hydrogen solubility.
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Zr-2.5 Nb 압력관에서 수소화물 석출에 따른 지르코늄 격자변형 및 응력 분포의 이방성
김성수,김영석,정용무,임경수 대한금속재료학회(대한금속학회) 2001 대한금속·재료학회지 Vol.39 No.2
The objective of this study is to investigate the effect of hydride precipitates on the distributions of the lattice distortion and stress in CANDU Zr-2.5Nb pressure tube. The three sections taken from CANDU Zr-2.5Nb tube, the longitudinal normal section(LS), the radial normal section(RS) and the transverse normal section(TS) were charged with hydrogen at 530℃ for 15 h. X-ray diffraction analysis was carried out on the sections with or without charged hydrogen using a X-ray diffractometer equipped with a position sensitive detector. The effect of hydride precipitates on the line broadening, the interplanar lattice spacing, and the macro-stress was determined from a change in the peak position and the half width of the diffraction lines {12.3} on the three sections. The hydride precipitates had an effect of increasing the interplanar lattice spacing of {12.3} only on the LS, causing tensile stress of as high as 400 ㎫ but decreased the interplanar lattice spacing on the TS causing it subjected to compressive stress. Based on a change in the distribution of line broadening with hydride precipitates on each section depending on the pole density of {12.3}, the preferential site for the precipitation of hydrides is discussed.
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