http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
UNS N06690 제1열 시제전열관의 U-굽힘성형에서 형상변화와 표면잔류응력
김우곤,장진성,국일현,주진원,김성청,Kim, Woo-Gon,Jang, Jin-Sung,Kuk, Il-Hiun,Joo, Jin-Won,Kim, Sung-Chung 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.1
Surface residual stresses as well as wall thickness and ovality changes after U-bending process on UNS N06690 row-1 heat exchanger tubes, were estimated. Surface residual stresses were measured by Hole Drilling Method(HDM), calculating the stresses from relieved strains of 3 rosette strain gages. After bending of the tubes, dimensional tolerances for wall thickness and ovality were satisfied with ASTM requirements. Residual stresses at the extrados were introduced with compressive stress(-) by bending operations, and its maximum value reached-319 MPa in axial direction at ${\phi}=0^{\circ}$ in position. Tensile residual stresses(+) of ${\sigma}_zz=45$ MPa,${\sigma}_zz=25$ MPa were introduced in the intrados surface at position of ${\phi}=0^{\circ}$ Maximum tensile residual stress of 170 MPa was detected on the flank side at position of ,${\phi}=95^{\circ}$i.e., at apex region. It appeared that higher stress gradients were generated at the irregular transition regions. In the trend of residual stress changes with U-bend position, the extrados is related with the changes of ovality and the intrados is related with the changes of wall thickness.
참조응력을 이용한 316LN 스테인리스강의 크리프 해석
김우곤,류우석,Kim, Woo-Gon,Ryu, Woo-Seog 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.10
Creep damage using a reference stress(RS) was analyzed for type 316LN stainless steel. The generalized K-R equation was reconstructed into the RS equation using a critical stress value $\sigma$. The RS equation was derived from the critical stress in failure time $t_f$ instead of material damage parameter $\omega$, which indicates the critical condition of collapse or approach to gross instability of materials during creep. For obtaining the reference stress, a series of creep tests and tensile tests were conducted with at 55$0^{\circ}C$ and $600^{\circ}C$. The stress-time data obtained from creep tests were applied to the RS equations to characterize the creep damage of type 316LN stainless steel. The value of creep constant r with stress levels was about 18 at 55$0^{\circ}C$ and 21 at $600^{\circ}C$. This value was almost similar with r = 24 in the K-R equation, which was obtained by using damage parameter $\omega$. Relationship plots of creep failure strain and life fraction $(t_f /t_r)$ were also obtained with different λ values. The RS equation was therefore more convenient than the generalized K-R equation, because the measuring process to quantify the damage parameter $\omega$ such as voids or micro cracks in crept materials was omitted. The RS method can be easily used by designers and plant operator as a creep design tool.
Type 316L 강의 고온 크리프 및 크리프 균열성장 거동
김우곤(Woo-Gon Kim),I.N.C. Kusuma,박재영(Jae-Young Park),이형연(Hyeong-Yeon Lee),김선진(Seon-Jin Kim) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
The high-temperature material behaviors of type 316L stainless steel (SS), which is used for a main structural material of a sodium-cooled fast reactor (SFR), were investigated by the tension, creep, and creep crack growth tests. The tension tests were performed at R.T. to 650℃, the creep tests were performed under different applied loads at 600℃ and 550℃, and the creep crack growth (CCG) tests were conducted using 1/2-inch compact tension specimens at 600℃. The creep test data were analyzed using various creep plots and fracture microstructures, and compared with RCC-MRx. The CCG rate (CCGR) for type 316L was constructed using a C* fracture parameter, and the CCGR of type 316L was compared with those of type 316 SS and 316LN. The creep strength decreased with an increase in rupture time, and the creep rate increased with an increase in stress. The rupture ductility decreased slightly with an increase in rupture time. The present tested data showed higher creep strength than that of RCC-MRx, and marginal differences to RCC-MRx in the creep rate. In the CCGR test results, type 316L was lower in the CCGR than type 316SS, and type 316L and 316LN were almost similar in the CCGR.
Tensile Behavior and Full-range Stress-Strain Curves for Gr. 91 Steel
Woo-Gon Kim(김우곤),Jae-Young Park(박재영),I.M.W. Ekaputra,Hyeong-Yeon Lee(이형연),Seon-Jin Kim(김선진) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
High-temperature tensile behavior for Grade 91 (Gr. 91) steel for use of a sodium-cooled fast reactor (SFR) structure was investigated, and full-range stress-strain curves were described in terms of RCC-MRx procedures (French SFR code) and four constitutive equations: power-law form, logarithmic form, exponential form, and modified form (powerlaw + exponential). To do this, a series of high-temperature tensile data was obtained from the tensile tests performed with a strain rate of 6.67 x10-4 (1/s) at R.T to 650oC. On the basis of experimental tensile data, full-range stress-strain curves were designed by RCC-MRx procedures. In addition, a modified constitutive equation in terms of a combination of power-law form and exponential form were proposed to well describe the full-range stress-strain curves, and the suitable equation in the four equations was investigated by fitting to the experimental curves. Results showed that the stress-strain curves designed by RCC-MRx were in accordance with the experimental curves at all of the temperature ranges, and a proposed modified equation was found to be superior in modeling of the stress-strain curves to the other equations. It can be conveniently used in modeling full-range stress-strain curves without calculation procedures in RCC-MRx code.
Comparison of Creep Crack Growth Rates on the Base and Welded Metals of Modified 9Cr-1Mo Steel
Woo-Gon Kim(김우곤),Jae-Young Park(박재영),Song-Nan Yin(윤송남),Sung-Ho Kim(김성호),Yong-Wan Kim(김용완),Seon-Jin Kim(김선진) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
This paper is to compare creep crack growth rates (CCGR) on the base metal (BM) and welded metal (WM) of modified 9Cr-1Mo steel for Gen-IV reactors. Welded specimens were prepared by Shielded Metal Arc Weld (SMAW) method. To obtain material properties for the BM and welded metal, a series of creep and tensile tests was conducted at 600℃, and CCG tests was also performed using 1/2 compact tension specimens under different applied loads at 600℃. Their CCGR behaviors were analyzed by using the empirical equation of the da/dt vs. C<SUP>*</SUP> parameter and compared, respectively. It appeared that, for a given value of C<SUP>*</SUP>, the rate of creep propagation was about 2.0 times faster than in the WM than the BM. This reason is that a creep rate in the WM was largely attributed when compared with that in the BM. From this result, it can be utilized for assessing the rate of creep propagation on the BM and WM of the G91 steel.
외식산업 사회교육 프로그램 만족도와 선호도에 관한 탐색적 연구
김우곤(Kim Woo Gon),유영진(Yoo Young Jin) 한국외식경영학회 2000 외식경영연구 Vol.2 No.1
The propose of this study was to identify the problems of the social training program and to suggest the improving methods by analyzing the preference level and the satisfaction level of the social training program in dining industry while investigating the current statuses of the dining industry in Korea and the social training program at Korean colleges. A total of 338 valid responses ware analyzed after 15 questionnaires out of the total of 353 questionnaires collected did not meet the basic requirements for one month. In order to analyze the collected valid responses, SPSS / WIN 7.5 package program was utilized to employ the frequency analysis, the regression analysis, ANOVA, etc. In terms of the satisfaction level of the social training program in dining industry, the most influential factors were identified as the college social training centers, followed by private cooking schools in order; in terms of the preference level of the organizing body of each social training program, college professors, executive officers of social organization, and concurrent professors with practical experiences were identified as the most influential in order. In terms of the preference level of the training methods, the lecture was most influential.