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Hf 가 첨가된 Fe-30at.%A1-5at.%Cr 합금의 미세조직 및 열간압연가공 특성
윤계림(Kye Lim Yoon),이도재(Doh Jae Lee),백대화(Dae Hwa Baek),이경구(Kyung Ku Lee) 한국주조공학회 2001 한국주조공학회지 Vol.21 No.6
N/A This study was carried out to examine the effects of adding 0.3at.%Hf in Fe-30at.%Al-5at.%Cr alloy on the variation of microstructures and hot workability. The effect of hot rolling on mechanical properties was estimated by measuring the elongation and tensile strength after rolling at 800 and 1000 respectively. Microstructure of Fe-30at.%Al-5at.%Cr alloy was consisted of large equiaxed grains and it was changed to quasi-equiaxed or columnar structures by adding 0.3at.%Hf to Fe-30at.%Al-5at.%Cr alloy. Every specimens showed a decreased tensile strength after hot rolling compared to that of before rolling. The elongation was increased by hot rolling. Remarkable changes in elongation by hot rollong was observed such as from 1.4% to 4.5% elongation at the specimen of 0.3at.%Hf added to Fe-30at.%Al-5at.%Cr. Fe-30at.%Al-5at.%Cr alloy showed typical cleavage fracture on tensile failure and hot rolling has negligible effects on fracture mode in this alloy. However at the alloy containing Hf fracturemode was changed by hot rolling from intergranular to mixed intergranular and transgranular fracture mode.
가공 열처리에 따른 Ti-10Ta-10Nb합금의 미세조직 및 기계적 특성 변화
이도재 ( Doh Jae Lee ),황주영 ( Ju Young Hwang ),이경구 ( Kyung Ku Lee ),윤계림 ( Kye Lim Yoon ),전충극 ( Choong Geug Jun ) 한국열처리공학회 2005 熱處理工學會誌 Vol.18 No.2
N/A Both commercially pure titanium and Ti-6AI-4V alloy have been widely used as biomaterials because of their excellent biocompatibility, corrosion resistance and mechanical properties. However, in recent years, vanadium has been found to cause cytotoxic effects and adverse tissue reactions, while aluminium has been associated with potential neurological disorders. A newly designed α+ß type Ti alloy, Ti-10Ta-10Nb alloy showed superior properties to CP Ti and Ti-6AI-4V alloy in the point of biomaterial, and elucidated the future uses as a biomaterial. Microstructural changes of Ti-10Ta-10Nb alloy after hot-rolling, warm-rolling, solution and aging treatment were investigated. According to TEM results, the microstructures after solution treatment were composed of mostly α phase with a trace of ß phase due to adding ß-phase stabilizer tantalum and niobium. The microstructures after warm-rolling is coarse and elongated a phase and hot rolling resulted in very fine a widmansta¨tten. The highest value of hardness was obtained by aging treatment at 400℃ for 20hr in which microstructure consisted of very fine a phase in β matrix.
이도재(Doh-Jae Lee),이광민(Kwang-Min Lee),이경구(Kyung-Ku Lee),박범수(Bum-Su Park),김수학(Soo-Hak Kim),전충극(Choong-Geug Jun),윤계림(Kye-Lim Yoon) 한국표면공학회 2004 한국표면공학회지 Vol.37 No.1
The oxidation behavior of Ti-Nb alloys was studied in dry atmosphere. After vacuum arc melting and hot rolling treatment, Ti-Nb alloys were oxidized at 450℃~750℃. The oxidation behaviors between matrix and oxide scale were analyzed by SEM, XPS and XRD. Ti-Nb alloys had higher oxidation resistance than pure Ti at 750℃. XPS analysis of oxide film revealed that TiO₂ oxide was formed on the top of surface. The weight gains during the oxidation increase rapidly at temperature above 600℃ which obey the parabolic law.
수치지도 등고선의 Model Key Point 추출과 Progressive Sampling에 의한 수치지형모델 생성
이선근,염재홍,임새봄,김계림,이동천,Lee, Sun-Geun,Yom, Jae-Hong,Lim, Sae-Bom,Kim, Kye-Lim,Lee, Dong-Cheon 한국측량학회 2007 한국측량학회지 Vol.25 No.6
일반적으로 수치지도의 등고선은 항공사진을 해석 및 수치 도화기 상에서 입체시 하여 동일한 높이의 점들을 3차원으로 측정하고 도화하여 생성되므로 등고선 도화는 작업량이 많고 도화사의 주관적인 판단과 경험에 의해 결정된다. 그러므로 지형의 형태와 특성을 묘사하는 등고선의 도화는 도화사의 풍부한 경험이 요구된다. 또한 국내의 수치지도는 수치지형모델(DTM) 데이터를 포함하고 있지 않으므로 DTM이 필요한 경우 대부분 등고선 데이터로부터 간접적으로 생성한다. 본 연구에서는 지형의 특성에 대한 중요한 정보를 포함하고 있는 model key point를 등고선에서 추출하고, 이를 기반으로 지형적 특성을 고려하여 DTM의 격자간격을 효율적이고 융통적으로 조절하여 정량적 및 정성적인 측면에서 최적의 데이터를 이용하여 DTM을 생성하는 방법을 제안한다. 이를 위하여 progressive sampling 기법을 적용하여 지형이 복잡하여 기복이 큰 산악지역에는 격자간격을 작게하고 지형이 완만한 지역은 격자간격을 상대적으로 크게한다. 그러므로 고정된 하나의 격자간격을 사용하지 않고 지역별로 서로 다른 격자간격을 가지는 다중격자 DTM을 생성하였다. 다중격자 DTM은 용량이 최적화되어 계산량이 적고, 신속한 디스플레이 할 수 있는 장점이 있다. In general, contours in digital vector maps, which represent terrain characteristics and shape, are created by 3D digitizing the same height points using aerial photographs on the analytical or digital plotters with stereoscopic viewing. Hence, it requires lots of task, and subjective decision and experience of the operators. DTMs are generated indirectly by using contours since the national digital maps do not include digital terrain model (DTM) data. In this study, model key points which depict the important information about terrain characteristics were extracted from the contours. Further, determination of the efficient and flexible grid sizes were proposed to generate optimal DTM in terms of both quantitative and qualitative aspects. For this purpose, a progressive sampling technique was implemented, i.e., the smaller grid sizes are assigned for the mountainous areas where have large relief while the larger grid sizes are assigned for the relatively flat areas. In consequence, DTMs with multi-grid for difference areas could be generated instead of DTMs with a fixed grid size. The multi-grid DTMs reduce computations for data processing and provide fast display.
생체용 Ti합금의 산화거동에 미치는 Ta 및 Nb 첨가의 영향
이도재,오태욱,박범수,김수학,전충극,윤계림,Lee Doh-Jae,Oh Tae-Wook,Park Bum-Su,Kim Soo-Hak,Jun Choong-Geug,Yoon Kye-Lim 한국재료학회 2004 한국재료학회지 Vol.14 No.3
The oxidation behaviors of Ti-10Ta-10Nb alloy and Ti-6Al-4V alloy were studied in dry air atmosphere. Specimens were melted in consumable vacuum arc furnace and homogenized at $1050^{\circ}C$ for 24 h. Hot rolling was performed at $1000^{\circ}C$. Specimens of the alloys were oxidized as the temperature range $400~650^{\circ}C$ for 30 min. The oxidation behavior of the alloys was analysed by optical microscope, SEM/EDX, XRD, XPS and TGA. Immersion test was performed in 1% Lactic acid. In the microscope observation, oxide layer of Ti-10Ta-10Nb alloy was denser and thinner than Ti-6Al-4V's. The weight gains during the oxidation rapidly increased at the temperature above $600^{\circ}C$ in Ti-6Al-4V's alloy and$ 700^{\circ}C$ in Ti-10Ta-10Nb alloy. According to XRD results, oxide layers were composed of mostly $TiO_2$(rutile) phase. It was analysed that the passive film of the Ti alloys consisted of $TiO_2$ through X-ray photoelectron spectroscopy(XPS) analysis.
안진환,이계림,나기남 대한슬관절학회 1989 대한슬관절학회지 Vol.1 No.2
The anterior cruciate ligament has an important role in maintenance of the stability of the knee joint. The incidence of anterior cruciate ligament injury is increasing. Various methods of repair of acute rupture of the anterior cruciate ligament through the arthrotomy technique have been used widely, but the arthroscopic repair is a relatively new technique. This arthroscopic technique is idealy applicable for rupture at femoral attachment site. The most important advantage of the arthroscopic repair technique is preservation of ruptured anterior cruciate ligament as compared with the conventional arthrotomy technique. Authros performed arthroscopic anterior cruciate repair in 2 cases, and the result was very satisfactory with short term follow-up.