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Guo Xian,Jeong mok Oh(오정목),Junghoon Lee(이정훈),Sangmyung Cho(조상명),Jongtak Yeom(엄종탁),Yoonsuk Choi(최윤석),Namhyun Kang(강남현) 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.5
Wire arc additive manufacturing (WAAM) is a process that combines an electric arc as a heat source and a wire as feedstock to build a component layer by layer. In arc welding, heat input is an important characteristic because it influences the cooling rate, which could affect the mechanical properties and microstructure of the deposition part. We investigated the effect of heat input on the microstructure and mechanical property of the additive layer manufactured for Ti64 alloys. High-heat input (H; 1 kJ/mm) produced a columnar grain exhibiting a large anisotropic property of tensile strength. Low-heat input (L; 0.5 kJ/mm) transformed the columnar grains to the equiaxed ones, and its reason was associated with the solidification cooling rates accelerated. However, the H specimens exhibited a larger tensile strength and hardness than the L specimens, which can be explained by volume fraction of the hardened phase (α’ martensite and secondary α). The microstructure in H and L specimens were further identified by SEM-EDX and TEM. The thermal history in the WAAM deposits was also simulated using finite element method. At the certain temperature gradient, the faster cooling rates produced the more fraction of the equiaxed grains. Furthermore, the H specimens exhibited more thermal cycles calculated to verify the condition that can produce more α’ martensite and secondary α. Therefore, the L specimen changed the grain structure to equiaxed one and reduced the anisotropy of tensile strength significantly.
Guo Xian,Jeong mok Oh(오정목),Junghoon Lee(이정훈),Sangmyung Cho(조상명),Jongtak Yeom(엄종탁),Yoonsuk Choi(최윤석),Namhyun Kang(강남현) 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.5
Wire arc additive manufacturing (WAAM) is a process that combines an electric arc as a heat source and a wire as feedstock to build a component layer by layer. In arc welding, heat input is an important characteristic because it influences the cooling rate, which could affect the mechanical properties and microstructure of the deposition part. We investigated the effect of heat input on the microstructure and mechanical property of the additive layer manufactured for Ti64 alloys. High-heat input (H; 1 kJ/mm) produced a columnar grain exhibiting a large anisotropic property of tensile strength. Low-heat input (L; 0.5 kJ/mm) transformed the columnar grains to the equiaxed ones, and its reason was associated with the solidification cooling rates accelerated. However, the H specimens exhibited a larger tensile strength and hardness than the L specimens, which can be explained by volume fraction of the hardened phase (α’ martensite and secondary α). The microstructure in H and L specimens were further identified by SEM-EDX and TEM. The thermal history in the WAAM deposits was also simulated using finite element method. At the certain temperature gradient, the faster cooling rates produced the more fraction of the equiaxed grains. Furthermore, the H specimens exhibited more thermal cycles calculated to verify the condition that can produce more α’ martensite and secondary α. Therefore, the L specimen changed the grain structure to equiaxed one and reduced the anisotropy of tensile strength significantly.
해양플랜트 탑사이드용 고압 볼밸브에 대한 구조 안전성 평가
오정식(Jeong-Sik Oh),김유일(Yooil Kim),정낙신(Nakshin Jeong),김상명(Sangmyung Kim) 한국해양공학회 2016 韓國海洋工學會誌 Vol.30 No.2
A high-pressure ball valve was developed, and both the structural strength and sealing performance were assessed based on a nonlinear finite element analysis. Different parts were modeled with solid elements and assembled, taking into account both contact and sliding effects. Three different loading scenarios were analyzed, including a high-pressure closure test and fire and shell test conditions. The structural safety of each part was checked under each loading condition, and the sealing performance was also investigated to validate the performance of the valve.
Guo Xian,Jeong mok Oh(오정목),Junghoon Lee(이정훈),Sangmyung Cho(조상명),Jongtak Yeom(엄종탁),Yoonsuk Choi(최윤석),Namhyun Kang(강남현) 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.5
Wire arc additive manufacturing (WAAM) is a process that combines an electric arc as a heat source and a wire as feedstock to build a component layer by layer. In arc welding, heat input is an important characteristic because it influences the cooling rate, which could affect the mechanical properties and microstructure of the deposition part. We investigated the effect of heat input on the microstructure and mechanical property of the additive layer manufactured for Ti64 alloys. High-heat input (H; 1 kJ/mm) produced a columnar grain exhibiting a large anisotropic property of tensile strength. Low-heat input (L; 0.5 kJ/mm) transformed the columnar grains to the equiaxed ones, and its reason was associated with the solidification cooling rates accelerated. However, the H specimens exhibited a larger tensile strength and hardness than the L specimens, which can be explained by volume fraction of the hardened phase (α’ martensite and secondary α). The microstructure in H and L specimens were further identified by SEM-EDX and TEM. The thermal history in the WAAM deposits was also simulated using finite element method. At the certain temperature gradient, the faster cooling rates produced the more fraction of the equiaxed grains. Furthermore, the H specimens exhibited more thermal cycles calculated to verify the condition that can produce more α’ martensite and secondary α. Therefore, the L specimen changed the grain structure to equiaxed one and reduced the anisotropy of tensile strength significantly.
차량내 PM2.5 초미세먼지 센서 적용 및 저감 기술에 대한 연구
신민재(Minjae SHIN),김보경(Bokyung KIM),오주환(Juhwan OH),임철훈(Choulhoon LIM),송상명(Sangmyung SONG) 한국자동차공학회 2022 한국자동차공학회 학술대회 및 전시회 Vol.2022 No.11
In a development of vehicle, it is a key strategy, what unique feature the car maker provides to customers, even though the required features of vehicle are quite various as per the country, culture. Accordingly, the car maker needs different production definition strategy for each sales country. According to the latest Renault internal survey with customers, named as ‘CARE strategy survey’, the European customers have less interest in the particulate matter in the air, than the Asian customers. The survey confirms that the customers from Korea, China, and India have lots of interest in the particulate matter and intend to pay cost for its sensing and air-purification function. In this study, we explain the PM2.5 system for Korean customer and market including its sensing technology, multi-media interface and air-purification based on the development experience and test results.