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Yielding Anisotropy of Rolling Textured High Purity α-Ti
Jong Woo Won(원종우),Yong-Hak Huh(허용학),Seong-Gu Hong(홍성구) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
The yield strength of rolling textured high purity -Ti was found to be significantly dependent on the loading direction, i.e., yielding anisotropy; normal direction (ND) > transverse direction (TD) > rolling direction (RD). Activation stresses for three important deformation modes (prismatic, basal, and pyramidal 〈a〉 slips) were calculated based on the Schmid factor (SF) and effective critical resolved shear stress. The calculation results revealed that the specific crystallographic orientation of the material, caused by rolling texture, influences the activity of each deformation mode by affecting the SF and this significantly varies with the loading direction, thereby inducing a change of a deformation mode dominating the material yielding. Prismatic 〈a〉 slip governed the yielding in the RD and TD, while basal 〈a〉 slip was responsible for the yielding in the ND.
불소가 도입된 광경화형 우레탄 아크릴레이트 올리고머의 합성 및 특성분석
원종우 ( Jong-woo Won ),박정현 ( Jung-hyun Park ),김주열 ( Ju-yeol Kim ),윤유정 ( Yoo-jung Yoon ),장기덕 ( Ki-deog Jang ),박명철 ( Myung-chul Park ),천제환 ( Jae Hwan Chun ),황진상 ( Jin-sang Hwang ) 한국접착및계면학회 2017 접착 및 계면 Vol.18 No.3
본 연구에서는 방수 성능이 개선된 디스플레이용 접착 소재를 개발하기 위해 불소 화합물을 도입한 Polybutadiene계 우레탄 아크릴레이트 올리고머를 합성하였다. 합성에 적용한 디올은 신뢰성 확보 측면에서 이중결합을 제거한 수첨 폴리부타디엔 디올 (HLBH-P2000)을 적용하였으며, 불소를 함유한 perfluoropolyether (HTPFPE) 디올을 공중합 하는 방법으로 불소 화합물을 올리고머의 주쇄사슬에 도입하였다. 디이소시아네이트는 Isophorone diisocyanate (IPDI)를 사용하여 합성을 진행하고, 마지막으로 2-hydroxyethyl acrylate (HEA)를 말단에 부가하여 불소가 도입된 올리고머를 합성하였다. 합성된 올리고머의 특성 평가 결과, HTPFPE의 함량이 증가할수록 접촉각은 증가하고 표면에너지는 감소하는 결과를 보였으며, 더불어 투습율 (WVTR) 또한 감소함을 확인하였다. 접착력은 HTPFPE의 함량 증가에 따라 감소하는 경향을 보였으며, HTPFPE의 함량이 증가함에 따라 접착력 감소 폭이 크게 증가하는 경향을 보였다. 본 연구의 결과로부터, 최근 이슈가 되고 있는 디스플레이 장치의 방수 소재로 적용이 가능한 접착제로서의 활용이 가능할 것으로 판단된다. In this study, to develop the adhesives with improved waterproof properties for display application, UV-curable urethane acrylate oligomers containing a fluorine moiety were synthesized from hydrogenated polybutadiene diol (HLBH-P2000), perfluoropolyether diol (HTPFPE), isophorone diisocyanate (IPDI) and 2-hydroxyethyl acrylate (HEA). The properties which were related waterproof performance such as contact angle, surface energy and water vapor transmission ratio (WVTR) of synthesized fluorine induced urethane acrylate oligomers were measured. As the HTPFPE content increased, the contact angle also increased from 97.9 degree to 104.4 degree. The surface energy and WVTR decreased as the HTPFPE content increased. The adhesion strength also decreased according to the HTPFPE content increased, and the adhesion strength reduction had greatly increased as the HTPFPE content increased. The findings of this study will be beneficial for developing waterproofing adhesives in the field of display which has recently been a waterproof issue.
연속냉각 중 산소함량이 Ti-5Al-2.5Fe 합금의 상변태 거동에 미치는 영향
김도헌 ( Do-heon Kim ),원종우 ( Jong Woo Won ),정대원 ( Dae-won Jeong ),이학성 ( Hak-sung Lee ),윤석영 ( Seog-young Yoon ),현용택 ( Yong-taek Hyun ) 대한금속재료학회(구 대한금속학회) 2017 대한금속·재료학회지 Vol.55 No.9
Abstract: The effects of oxygen content on the β to α phase transformation of the Ti-5Al-2.5Fe alloy during continuous cooling were investigated by varying the oxygen content between 0.08 - 0.41 wt%. Dilatometer tests were performed at cooling rates of 0.05 - 100 ℃/s combined with microstructure observation to examine phase transformation mechanisms and resulting microstructure. Our results showed that oxygen acted as a strong α phase stabilizer by increasing β-transus temperature, and promoted diffuse-controlled α phase transformation with hindering martensitic transformation. Depending on the oxygen content, the different transformation mechanism led to a distinct difference in microstructure evolution. As an oxygen content increased, α phase was developed in thicker lath forms and was globularized at a slow cooling rate, whereas the formation of acicular-shaped α phase was significantly reduced. Hardness behavior after cooling was discussed in the light of microstructure morphology and possible precipitation formation. Based on the analysis results, continuous cooling transformation diagrams of the investigated alloys were established. (Received March 2, 2017; Accepted May 8, 2017)
CoCrFeMnNi 고엔트로피합금 주조재의 미세조직 및 기계적 특성
강민주 ( Minju Kang ),원종우 ( Jong Woo Won ),임가람 ( Ka Ram Lim ),박상협 ( Sang Hyeop Park ),서성문 ( Seong Moon Seo ),나영상 ( Young Sang Na ) 대한금속ㆍ재료학회 2017 대한금속·재료학회지 Vol.55 No.10
In this study, we made large-scale ingots of CoCrFeMnNi high entropy alloy by vacuum induction melting. The as-cast CoCrFeMnNi high entropy alloy contained a high proportion of columnar structures with a few equiaxed grains, and showed single phase fcc solid solutions without macro segregation and low interstitial levels. The tensile properties along the three different loading directions were investigated at low-temperature and room temperature. A decrease in temperature led to an increase in yield and tensile strengths. The increase in anisotropy due to the columnar structure was negligible. Unlike wrought CoCrFeMnNi high entropy alloys, twins were actively formed in the specimen deformed at room temperature. Mechanical twinning was found to be a result of the coarse grain size, over 500 μm, of the as-cast CoCrFeMnNi high entropy alloy, which effectively reduced the critical stress for twinning. Charpy impact tests were also conducted, and the absorbed energy of the CoCrFeMnNi high entropy alloy showed no dependence on the temperature or loading directions. The results of this study provide an understanding of pilot-scale high entropy alloy castings, and are expected to be utilized as basic properties for manufacturing large-scale high entropy alloy castings, which are effective in severe environments. (Received May 23, 2017; Accepted June 4, 2017)
Tetramethylpyrazine이 LPS의 뇌실주입에 따른 생쥐 뇌조직의 Pro-Inflammatory Cytokines 발현에 미치는 영향
최용석 ( Yong Seok Choi ),원종우 ( Jong Woo Won ),유인우 ( In Woo Yoo ),신정원 ( Jung Won Shin ),김성준 ( Seong Joon Kim ),손낙원 ( Nak Won Sohn ) 대한본초학회 2013 大韓本草學會誌 Vol.28 No.1
Objectives : Tetramethylpyrazine (TMP) is an active ingredient in Ligusticum wallichii and has a wide range of neuroprotection effects. This study investigated anti-neuroinflammatory effect of TMP on brain regions in intracerebroventricular (i.c.v.) lipopolysaccharide (LPS)-treated C57BL/6 mice, Methods : TMP was administered intraperitoneally at doses of 10, 20, and 30 mg/kg at 1 h prior to LPS (3 mg/kg) i.c.v. injection. mRNA level of pro-inflammatory cytokines, including tumor necrosis factor-α (TNF- α), interleukin (IL)-1β and IL-6, was measured in the cerebral cortex, hippocampus, and hypothalamus tissue using real-time polymerase chain reaction at 24 h after the LPS injection. Cyclooxygenase-2 (COX-2) positive cells in the hypothalamus was also observed using immunohistochemistry at 24 h after the LPS injection, Results : At a dose of 30 mg/kg TMP significantly attenuated up-regulation of TNF-α and IL-1β mRNA in the cerebral cortex and IL-1β mRNA in the hippocampus. In the hypothalamus, doses of 20 mg/kg and 30 mg/kg TMP significantly attenuated up-regulation of TNF-α, IL-1β, and IL-6 mRNA induced by the LPS injection. In addition, TMP (30 mg/kg) significantly reduced the number of COX-2 positive cells in the hypothalamus, Conclusion : These results indicate that TMP has an anti-inflammatory effect on neuroinflammation, especially in the hypothalamus, induced by LPS i.c.v. injection and suggest that TMP-containing Ligusticum wallichii may play a modulatory role on the systemic responses following hypothalamic inflammation.