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김상재(Sang-Jai Kim),정용무(Yong-Moo Cheong),오동준(Dong-jun Oh),임경수(Kyung-Soo Im),김영석(Young-Suk Kim) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.8
The aim of this study was to obtain a better understanding of delayed hydride cracking (DHC) of Zr-2.5Nb pressure tube with crack growth direction. Curved compact tension (CCT) and cantilever beam (CB) specimens were used to determine the DHC velocity in the longitudinal and radial directions, respectively. DHC tests were conducted at 250 oC after charging the specimens with hydrogen to 60ppm H. The DHC velocity of the Zr-2.5Nb tube was anisotropic with crack growth direction: DHCV in the axial direction was 4 times faster than that in the radial direction and the incubation time till the growth of the DHC crack was 5 times faster in the axial direction than that in the radial direction This anisotropic DHC behavior of the Zr-2.5Nb tube with crack growth direction is discussed on the nucleation and growth pattern of hydrides on the cracking plane.
방향에 따른 Zr-2.5Nb 압력관의 DHC 임계응력확대세기, K<SUB>IH</SUB>
김상재(Sang-Jai Kim),김성수(Sung-Soo Kim),정용무(Yong-Moo Cheong),임경수(Kyung-Soo Im),김영석(Young-Suk Kim) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.8
The object of this study is to obtain a better understanding of delayed hydride cracking (DHC) of Zr-2.5Nb pressure tube with crack growth directions; the radial and axial direction of the tube. DHC tests were conducted at temperatures ranging from 160~280℃ on curved compact tension (CCT) and cantilever beam (CB) specimens with 60 ppm H to determine the threshold stress intensity factor, K<SUB>IH</SUB> in axial and radial directions of the Zr-2.5Nb tube, respectively. Over a temperature range of 160 ~ 250℃, K<SUB>IH</SUB> of the Zr-2.5Nb tube was constant independent of temperatures in both directions of the tube. K<SUB>IH</SUB> was higher in the radial direction than that in the axial direction: 5.84 ㎫√m in the axial direction and 8.44 ㎫√m in the radial direction. Furthermore, K<SUB>IH</SUB>had a strong dependence of the supersaturated hydrogen concentration in Zr-2.5Nb pressure tube. Thus, K<SUB>IH</SUB> was nicely described as a function of the supersaturated hydrogen concentration over TSSD independent of temperatures. K<SUB>IH</SUB> was discussed with the supersaturated hydrogen concentration and orientations.
장입한 수소량이 Zr-2.5Nb 압력관의 K<SUB>1H</SUB>에 미치는 영향
김상재(Sang-jai Kim),김영석(Young-suk Kim),임경수(Kyung-soo Im),송택호(Song-taek Ho) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.8
The aim of this study was to obtain a better understanding of delayed hydride cracking (DHC) of Zr-2.5Nb pressure tube with hydrogen concentration. DHC tests were conducted at 280℃ on Curved Compact Tension (CCT) and Cantilever Beam (CB) specimens with 60, 80, 100 ppm H to determine the threshold stress intensity factor, K1H in axial and radial directions of the Zr-2.5Nb tube, respectively. Over a hydrogen concentraion range of 80~100 ppm, K1H for the Zr-2.5Nb tube 5.84 ㎫√m in the axial direction and 8.4 ㎫√m in the radial direction, both of which were constant independent of hydrogen concentraion, However, at 60ppm, K1H increased unexpectedly to a higher value. Based on the results, K1H for Zr-2.5Nb tube is discussed with the fracture surface and a supersaturated concentration of hydrogen.
Zr-2.5Nb 압력관에서 균열방향에 따른 K<SUB>1H</SUB>
김상재(Sang-Jai Kim),박순삼(Soon-Sam Park),임경수(Kyung-Soo Im),정용무(Yong-Moo Cheong),김영석(Young-Suk Kim) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.3
The aim of this study was to obtain a better understanding of delayed hydride cracking (DHC) of Zr-2.5Nb pressure tube with crack growth direction. DHC tests were conducted at temperatures ranging form 160~280℃ on Curved Compact Tension (CCT) and Cantilever Beam (CB) specimens with 60 ppm H to determine the threshold stress intensity factor, K1H in axial and radial directions of the Zr-2.5Nb tube, respectively. Over a temperature range of 160~250℃, K1H for the Zr-2.5Nb tube 5.84 ㎫ √m in the axial direction and 8.4 ㎫ √m in the radial direction, both of which were constant independent of temperatures, However, at 280℃, K1H increased unexpectedly to a higher value. Based on the results, K1H for Zr-2.5Nb tube is discussed with the orientation, hydride habit plane and a supersaturated concentration of hydrogen.
김상재(Sang-Jai Kim),임경수(Kyung-Soo Im),김영석(Young-Suk Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.8
The aim of this study was to obtain a better understanding of delayed hydride cracking (DHC) of Zr-2.5Nb pressure tube with hydrogen concentration. After the ratcheting heat treatment, DHC tests were conducted at 200 and 250℃ on Cantilever Beam (CB) specimens with 60, 80ppm H to determine the threshold stress intensity factor, K<SUB>1H</SUB> in radial direction of the Zr-2.5Nb tube. Over a hydrogen concentration range of 80 ppm, K<SUB>1H</SUB> for the Zr-2.5Nb tube 13 ㎫ vm, However, at 60ppm, K<SUB>1H</SUB> increased unexpectedly to a higher value at 250℃. Based on the results, K<SUB>1H</SUB> for Zr-2.5Nb tube is discussed with the fracture surface and a supersaturated concentration of hydrogen..
김상재(Sang-Jai Kim),정일석(Ill-Seok Jeong),임경수(Kyung-Soo Im),김영석(Young-Suk Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
The aim of this study was to obtain a better understanding of delayed hydride cracking (DHC) of Zr-2.5Nb pressure tube with hydrogen concentration. DHC tests were conducted at 150, 200 and 250 ℃ on cantilever beam specimens with 60 and 80ppm H, respectively. The threshold stress intensity factor, K1H in radial direction of the Zr-2.5Nb tube were determined with and without the ratcheting heat treatment. Ratcheting heat treatment specimens had a little high K1H value from most temperature range. At the hydrogen concentration of 80 ppm, K1H for the Zr-2.5Nb tube was 13 MPam<SUP>1/2</SUP> with the ratcheting heat treatment. However, with the hydrogen concentration decreasing to 60ppm, K1H increased unexpectedly to a higher value at 250 ℃. Based on the results, K1H for Zr-2.5Nb tube is discussed with a supersaturated concentration of hydrogen.
정일석(Ill-Seok Jeong),김상재(Sang-Jai Kim),홍승열(Sung-Yull Hong) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
Among published environmental fatigue test data of stainless steels, Type 304 SS, Type 316 SS, Type 316N SS, Type 316 Weld SS, and cast stainless steel CF8M in Japan and U.S., useful data were quoted for analyzing the effect of sensitizing stainless steels in LWR environments. Temperature of the test data are 288~325℃ which is operating temperature range of LWR plants. Data were classified in terms of dissolved oxygen levels, strain rates in tension stroke, and sensitization. Then data were compared with logarithmic graph of vertical strain rate and horizontal fatigue life. Trend of sensitization was investigated for each type of stainless steels.
GTA 용접처리한 Zircaloy-4판재의 미세조직 및 기계적 성질
조충형(Chung-Hyung Joh),김상재(Sang-Jai Kim),김선식(Seon-Sik Kim),임경수(Kyung-Soo Im),김영석(Young-Suk Kim) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.8
To predict degradation of the reflector vessel made of annealed zircaloy-4 alloys their microstructures and tensile properties were investigated because irradiation growth strongly depends on metallurgical variables as composition, dislocation density, texture, grain size and residual stress. The plate has fully recrystallized grains, low dislocation density, two kinds of second phase particles as Zr(Fe,Cr)₂ and Zr₃Fe or Zr(Fe, Cr)₂, and a texture where most of basal poles are oriented toward the direction normal to thickness. Further study is necessary to evaluate basal pole intensity, f<SUB>L</SUB> with high confidence because its small change strongly affects the irradiation growth. The plate shows that higher YS, similar strength and larger elongation in the RD, compared to those in the direction normal to the RD. Welded region shows somewhat lager strength and YS at RT and smaller elongation than matrix. The welded region is concluded to have low residual stress as a results of post-weld anneal and similar hardness as that of matrix.
부명환(Myung-Hwan BOO),조충형,김상재(Sang-Jai KIM),임경수,김영석(Young-Suk KIM),Dong-Jun OH,Sung-Soo KIM 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.3
The aim of this study is to investigate fracture toughness of a Zr-2.5Nb pressure tube with temperature. The tensile and fracture toughness tests were performed at temperatures ranging from room temperature to 300℃ on tensile and curved compact tension, CCT specimens. The CCT specimens were directly cut from the tube retaining original curvature using wire cutting machine. The Zr-2.5Nb tube had a decrease in yield and tensile strengths with increasing temperature. However, its elongation had a maximum at 150℃ followed by a decrease with increasing temperatures. The loss of ductility which was stricking in the temperature range of 200~250℃ determined the fracture toughness resistance, dJ/da of the Zr-2.5Nb tube with temperature, resulting in the maximum in the range of 100~150℃. The temperature dependence of the fracture toughness for the Zr-2.5Nb tube is discussed fracture in association with the formation of secondary crack on the fractured surfaces.
정일석(Ill-Seok Jeong),이용성(Yong-Sung Lee),김상재(Sang-Jai Kim),송택호(Taek-Ho Song),조선영(Sun-Young Cho) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
Environmental fatigue crack propagation of CF8M and CF8A steels used in the domestic PWR were investigated on the simulated PWR condition(Temperature: 316 , Pressure: 15MPa). The test equipment for environmental fatigue(high temperature-high pressure loop, autoclave, load frame, measurement system) were designed. As-received and 60-year aged specimens were used in the test. To compare with environmental fatigue test, another test was performed in the air condition. The fracture surface of specimens were difficult to verify the fracture modes such as striation, intergranular crack and cleavage and so on. As the ferrite content of CF8M is increased, more particles covered fracture surface were peeled.