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이축정렬된 Ni 금속모재에 RF 마그네트론 스퍼터링에 의해 증착된 $CeO_2$ 및 $Y_2O_3$ 완충층 박막 특성
오용준,라정석,이의길,김찬중,Oh, Y.J.,Ra, J.S.,Lee, E.G.,Kim, C.J. 한국초전도학회 2006 Progress in superconductivity Vol.7 No.2
We comparatively studied the epitaxial growth conditions of $CeO_2$ and $Y_2O_3$ thin buffers on textured Ni tapes using rf magnetron sputtering and investigated the feasibility of getting a single mixture layer or sequential layers of $CeO_2$ and $Y_2O_3$ for more simplified buffer architecture. All the buffer layers were first deposited using the reducing gas of $Ar/4%H_2$ and subsequently the reactive gas mixture of Ar and $O_2$, The crystalline quality and biaxial alignment of the films were investigated using X-ray diffraction techniques (${\Theta}-2{\Theta},\;{\phi}\;and\;{\omega}\;scans$, pole figures). The $CeO_2$ single layer exhibited well developed (200) epitaxial growth at the condition of $10%\;O_2$ below an $450^{\circ}C$, but the epitaxial property was decreased with increasing the layer thickness. $Y_2O_3$ seldom showed optimum condition for (400) epitaxial growth. The sequential architecture of $CeO_2/Y_2O_3/CeO_2$ having good epitaxial property was achieved by sputtering at a temperature of $700^{\circ}C$ on the initial $CeO_2$ bottom layer sputtered at $400^{\circ}C$. Cracking of the sputtered buffer layers was seldom observed except the double layer structure of $CeO_2/Y_2O_3$.
소형펀치시험에 의한 연성-취성천이온도 평가 및 국부파괴강도 해석에 의한 표준시험법과 연계성 분석
오용준(Yong Jun Oh),최병찬(Byung Chan Choi),홍준화(Jun Hwa Hong) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.3
Ductile-brittle transition temperatures for the reactor pressure vessel(RPV) steels were determined using a small punch(SP) test and compared to the results from the Charpy impact test and fracture toughness test using a pre-cracked Charpy V-notched(PCVN) specimen in accordance with ASTM E 1921. The correlation between the transition temperatures from the SP test and standard specimen tests was investigated on the theoretical bases regarding the local criteria for cleavage fracture for different specimen geometries and loading conditions. SP test was performed for the seven conventional RPV steels in the temperature range of RT to -196℃. The samples were taken from 1/4T location of the vessels and machined into 10×10×0.5㎜ dimension. SP transition temperature (T<SUB>sp</SUB>) determined at the middle of upper and lower SP energies showed a good correlation with Charpy index temperature, T<SUB>41J</SUB>ㆍFurthermore, it was found that the T<SUB>sp</SUB> had a meaningful correlation with T<SUB>o</SUB> value from the PCVN test. The finite element(FE) calculation for the SP and PCVN test specimens gave a clue to the correlation. Fracture in SP specimen occurred at the highest stress and strain location and the local fracture stress at the cleavage initiation location for SP specimens showed a linear relationship with that for PCVN specimens in the transition region.
오용준(Oh Young June),윤갑식(Yun Kap Sik) 한국지역개발학회 2016 韓國地域開發學會誌 Vol.28 No.1
This research analyzed the effect of the development plan of the Naepo New Town. The Naepo New Town is one of the metropolitan administrative cities, differentiated from the existing cities. To overall identify the intention of the plan, the study analyzed the city development plan rather than the district unit plan. According to the result, first, higher satisfaction for living intention and living environment as the Naepo New Town had a difference from the existing new towns. Second, there was the highest satisfaction for parks and green spaces as well as urban disaster prevention, and it was identified that selfsufficiency and building the living environment was important. Third, among the eight specialization plans for the Naepo New Towns, there was a high satisfaction for public design and parks and green spaces and a low satisfaction for education policy and bicycle path. In addition, the techniques to design the crime preventive environment and specialized university were analyzed as the main project. Lastly, the most important factor that influenced satisfaction for the living environment of the Naepo New Town was infrastructure, followed by land use, parks and green spaces, income, traffic management and occupation. This study is meaningful in that a comparative analysis on the planning elements affecting local residents'satisfaction was empirically conducted by targeting the residents in the Naepo New Town.
경수로 원전 가압기 밀림배관의 저주기 피로 수명 및 파괴 특성평가
오용준(Yong Jun Oh),황태복(Tai Bok Hwang) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.8
Low cycle fatigue(LCF) properties of SS 347 and 316N stainless steels used for PWR surgeline piping were evaluated at room temperature and plant operating temperature of 330℃ and the resistance to LCF in the two steels was compared in view of the underlying microstructures. LCF tests were performed for cylindrical round specimens with 8nun-gauge length and 7㎜-outer/4㎜-inner diameters using hydraulic dynamic testing machine. For SS347, thermal-mechanical fatigue properties were additionally evaluated in the temperature range of 100 to 330℃ using the induction heating and air cooling system linked to the LCF test machine. SS316N showed longer fatigue life than SS347 at both of RT and 330℃. Higher test temperature resulted in shorter fatigue life in SS316N while similar fatigue lives in SS347. The similar lives in SS347 were attributed to the different cyclic deformation behavior at RT and 330℃. At room temperature, it was consistently work-hardened throughout the fatigue life while at 330℃ cyclically softened to the end of fatigue life. But, SS316N showed cyclic-softening at both of RT and 330℃. These different cyclic responses only came from the fine NbCN precipitates in the matrix in SS347. From the fractography of the tested samples, we additionally found different crack initiation mechanisms in the two steels. For SS316N, initial fatigue cracks at high input strain range mostly formed intergranularly while at small input strain range the tendency toward transgranular initiation became higher. But SS347 showed intergranular initiation regardless of input strain range.
오용준(Yong Jun Oh),이봉상(Bong Sang Lee),홍준화(Jun Hwa Hong) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.8
A small punch (SP) test was performed to evaluate the ductile-brittle transition temperature shift by neutron irradiation in reactor pressure vessel (RPV) steels. The results were compared to the standard transition temperature shifts from Charpy test and Master Curve fracture toughness test in accordance with the ASTM standard E1921. The samples were taken from 1/4T location of the vessel thickness and machined into 10×10×0.5mm dimension. Irradiation of the steels was carried out in the research reactor at KAERI (HANARO) at about 290℃ to the different fluence levels respectively. SP tests were performed in the temperature range of RT to -196℃ using a 2.4mm diameter ball. For the materials before and after irradiation, SP transition temperatures (T<SUB>sp</SUB>), which are determined at the middle of upper and lower SP energies, showed a linear correlation with the Charpy index temperature, T<SUB>41J</SUB>. But, the transition temperature shift from the Charpy test (ΔT<SUB>41J</SUB>) shows better correlation with the transition temperature shift (ΔT<SUB>sp(E)</SUB>) at a specific SP energy level (E) than that (ΔT<SUB>sp</SUB>) determined at the middle energy of SP curve. The T<SUB>sp(E)</SUB> had a meaningful correlation with the reference temperature (T<SUB>o</SUB>) from the master curve method using a pre-cracked Charpy V-notched (PCVN) specimen. From the microscopic approach to the fracture mechanism in the SP and standard PCVN specimens, the authors found a linear correlation between local fracture stresses in the two different specimens. This provides the feasibility for applying the SP technique to predicting T<SUB>o</SUB> value from the standard test.
논문 : Nb 첨가 오스테나이트계 내열 스테인리스강의 열기계적 피로 수명 및 변형 거동
오용준 ( Yong Jun Oh ),박중철 ( Joong Cheul Park ),양원존 ( Won Jon Yang ) 대한금속재료학회(구 대한금속학회) 2011 대한금속·재료학회지 Vol.49 No.7
Thermomechanical fatigue (TMF) behavior of heat resistant austenitic stainless steel was evaluated in the temperature range from 100℃ to peak temperatures of 600 to 800℃; The fatigue lives under TMF conditions were plotted against the plastic strain range and the dissipated energy per cycle. In the expression of the inelastic strain range versus fatigue life, the TMF data obtained at different temperature ranges were located close to a single line with a small deviation; however, when the dissipated energy per cycle, calculated from the area of the stress-strain hysteresis loops at the half of the fatigue life, was plotted against the fatigue life, the data showed greater scattering than the TMF life against the inelastic strain range. A noticeable stress relaxation in the stress-strain hysteresis curve took place at the peak temperatures higher than 700℃, but all specimens in this study exhibited cyclic hardening behavior with TMF cycles. Re-crystallization occurred during the TMF cycle concurrent with the formation of fine subgrains in the re-crystallized region, which is considered to cause the cyclic hardening of the steel.