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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.
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.
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.
아두이노 제어 보드와 스마트폰을 활용한 스마트 홈 알람시스템
오용준 ( Yong-jun Oh ),류근호 ( Keun-ho Ryu ) 한국정보처리학회 2014 한국정보처리학회 학술대회논문집 Vol.21 No.2
기존의 알람 어플리케이션은 음향 효과를 통한 자극이라는 단순한 방식으로 과거와 같거나 알람 해 제 방식이 유사한 알람 어플리케이션들이다. 이러한 기존의 방식을 벗어나 알람을 해제하려는 사용자에게 질문을 하고 그에 대한 답변을 Google TTS로 입력받아 알람을 끌 수 있도록 하였다. 또한 알람 종료 시 블루투스 통신을 이용하여 사용자가 입력한 값에 따라 아두이노를 통하여 실내의 조명과 커튼을 제어하여 더 효과적인 알람 효과를 낼 수 있도록 구현하였다.
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.
박종원,강승민,오용준,Park, Jong Won,Kang, Seoung Min,Oh, Yong Jun 한국강구조학회 2007 韓國鋼構造學會 論文集 Vol.19 No.6
국내의 경우 철골 보-기둥의 접합부에 브라켓 형식이 널리 사용되고 있다. 본 연구에서는 브라켓 형식의 접합부에서 약축방향의 접합부를 대상으로 접합부의 디테일을 바꿈으로서 보다 경제적이면서 동시에 기존의 접합 디테일을 사용한 접합부와 구조적으로 유사한 성능을 발휘할 수 있는 접합부를 개발하였다. 접합 디테일을 다르게 한 4개의 접합부를 제안하고 이에 대해 경제성을 비교하였다. 또한 제안된 접합형식의 구조적 성능을 검증하기 위해 기존 접합 디테일을 포함하여 총 다섯 개의 시험체를 제작하고 이에 대한 최대내력 실험연구를 수행하였다. 4개의 제안된 접합형식 모두 기존의 접합형식에 비해 경제적인 것으로 나타났으며 최대내력 실험의 경우 한 접합형식을 제외하고 모두 보의 소성모멘트를 발휘할 수 있었으며 기존의 접합형식과 유사한 충분한 변형특성을 발휘할 수 있는 것으로 나타났다. Column-tree beam-to-column joints are widely used in moment-resisting frames in Korea. In this study, we proposed four different arrangements for weak-axis moment-resisting beam-to-column connections, which are more economical than the conventional connection, while developing similar structural performance. We investigated the proposed connections whose connection details were different from the conventional one. The experiment was also conducted on a total of five beam-to-column joint specimensto verify the structural performance of the proposed connections. All four connections proposed in this study were found to be more economical that the conventional connection. Three out of four specimens with proposed details were able to developa structural performance similar to that of the specimen with the conventional detail.