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Edge‑Cracking Behavior of CoCrFeMnNi High‑Entropy Alloy During Hot Rolling
원종우,Minju Kang,Heoun‑Jun Kwon,Ka Ram Lim,Seong Moon Seo,Young Sang Na 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.6
This work investigated edge-cracking behavior of equiatomic CoCrFeMnNi high-entropy alloy during hot rolling at rollingtemperatures 500 ≤ TR ≤ 1000 °C. Edge cracks did not form in the material rolled at 500 °C, but widened and deepened intothe inside of plate as TR increased from 500 °C. Edge cracks were most severe in the material rolled at 1000 °C. Mn–Cr–Otype non-metallic inclusion and oxidation were identified as major factors that caused edge cracking. The inclusions nearedge region acted as preferential sites for crack formation. Connection between inclusion cracks and surface cracks inducededge cracking. Rolling at TR ≥ 600 °C generated distinct inclusion cracks whereas they were not serious at TR = 500 °C, sonoticeable edge cracks formed at TR ≥ 600 °C. At TR = 1000 °C, significant oxidation occurred at the crack surface. Thisaccelerated edge crack penetration by embrittling the crack tip, so severe edge cracking occurred at TR = 1000 °C.
Ti-4Al-4Fe-0.25Si 합금의 고온변형거동과 미세조직발달에 관한 연구
원종우,이용문,염종택,이기영,이종수 대한금속재료학회(구 대한금속학회) 2016 대한금속·재료학회지 Vol.54 No.5
Hot deformation behavior of Ti-4Al-4Fe-0.25Si alloy with martensite microstructure was investigated by compression tests at temperatures of 1023 - 1173 K (α+β phase region) and strain rates of 10-3 - 1 s-1. By analyzing the deformation behavior, plastic deformation instability parameters including strain rate sensitivity, deformation temperature sensitivity, efficiency of power dissipation, and Ziegler’s instability were evaluated as a function of deformation temperature and strain rate, and they were further examined by drawing deformation processing maps. The microstructure evolution was also studied to determine the deformation conditions under which equiaxed α phase was formed in the microstructure without remnants or kinked α phase platelets and shear bands, these last two of which cause severe cracks during post-forming process. Based on the combined results of the processing maps and the microstructure analysis, the optimum α+β forging conditions for Ti-4Al-4Fe-0.25Si alloy were determined. (Received January 20, 2016)
원종우(Jong-woo Won),오현종(Hyun-jong Oh),장의선(Euee S. Jang) 한국방송·미디어공학회 2004 방송공학회논문지 Vol.9 No.3
In this paper, we proposed a new lossless image compression algorithm. Lossless image compression has been used in the field that requires the accuracy and precision. Thus, application areas using medical imaging, prepress imaging, image archival systems, precious artworks to be preserved, and remotely sensed images require lossless compression. The compression ratio from lossless image compression has not been saftisfactory, thus far. So, new method of lossless image compression has been investigated to get better compression efficiency. We have compared the compression results with the most typical comprssion methods such as CALIC and JPEG-LS. CALIC has shown the best compression-ratio among the existing lossless coding methods at the cost of the extensive complexity by three pass algorithm. On the other hand, JPEG-LS's compression-ratio is not higher than CALIC, but was adopted as an international standard of ISO because of the low complexity and fast coding process. In the proposed method, we adopted an adaptive predictor that can exploit the characteristics of individual images, and an adaptive arithmetic coding with multiple probability models. As a result, the proposed algorithm showed 5% improvement in compression efficiency in comparison with JPEG-LS and showed comparablel compression ratio with CALIC.
원종우,Chan Hee Park,이태경,이종수 대한금속·재료학회 2014 METALS AND MATERIALS International Vol.20 No.6
The aim of this work is to develop a constitutive model that can predict the flow behavior of pure Ti withdifferent interstitial concentrations and grain sizes. To build a database required for identifying materialconstants, three different grades of Ti were subjected to tensile tests at temperatures of 223, 300, 473, 673or 773 K and at a fixed strain rate of 103 s1. In the modeling procedure, the mechanical threshold stressmodel was further modified to capture both the hardening effects attributed to the changes in equivalentoxygen concentration (Oeq) and the softening effect caused by deformation heating at high strain rates. Thedeveloped model can reasonably predict the flow behavior of pure Ti having different Oeq (0.14-0.32 wt%),and grain size (14.5-90 μm) over a temperature range of 135 to 673 K, and a strain rate range of 2×104 to1400 s1.
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.
Role of Deformation Twins in Static Recrystallization Kinetics of High-Purity Alpha Titanium
원종우,이태경,홍성구,Yongmoon Lee,이정훈,Chong Soo Lee 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.6
The importance of deformation twins in static recrystallization kinetics of high-purity alpha titanium was investigatedby carrying out thermal annealing tests of deformed materials in combination with electron-backscatterdiffraction-based microstructural analysis. Prior to thermal annealing, the material was compressed to a truestrain of 0.22 along three directions to introduce different twinning characteristics. Our results showed thatdeformation twins substantially promoted the static recrystallization process by deepening the microstructuralinhomogeneity induced by the formation of twin boundaries and twinning-induced crystallographic latticereorientation. Twin morphology was also observed to be important because it influenced the extent of microstructuralinhomogeneity. Intersecting twin morphology, caused by the activation of multiple twin variants, was moreeffective than parallel twin morphology, caused by the activation of a single twin variant (or a twin variantpair), because it gave rise to more twin boundaries, more twin boundary junctions (intersections, triplejunctions, etc.), and greater in-grain crystallographic orientation spread.