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소성 가공 해석을 통한 티타늄 합금 볼트 열간 단조 공정 분석
최두선,김태민,항봉석,한유진,고강호,박정래,박규백,이정우,김도언,Choi, Doo-Sun,Kim, Tae-Min,Han, Bong-Seok,Han, Yu-Jin,Ko, Kang-Ho,Park, Jung-Rae,Park, Kyu-Bag,Lee, Jung-Woo,Kim, Do-Un 한국금형공학회 2020 한국금형공학회지 Vol.14 No.1
Titanium alloy has been in the spotlight as a core material in high-tech industries that require high strength and light weight because it has excellent strength and corrosion resistance and strength is higher than that of steel. Therefore, in various industries, existing steel products are intended to be replaced with titanium alloys. Titanium alloys can cause cutting tool breakage during cutting, and heat generated during cutting does not dissipate, accumulates in tools and workpieces, resulting in large wear and tear on thin workpieces. In addition, since titanium alloy is a metal with high chemical activity, the wear of the tool becomes more severe when the cutting speed is high, so machining of titanium bolt through cutting is very disadvantageous in terms of productivity. Therefore, the production of bolts using titanium alloys is being produced through a forging process to improve productivity and product quality. In this paper, hot forging molding analysis was performed on bolts used for fastening automobile parts using Ti-6Al-4V alloy, which is the most commonly used titanium alloy.
콘크리트의 염소이온 확산계수의 시간의존성에 대한 실험적 고찰
최두선(Choi Doo Sun),최재진(Choi Jae Jin) 대한토목학회 2009 대한토목학회논문집 A Vol.29 No.4A
콘크리트 중의 염화물이온 확산특성의 평가는 농도 차에 의한 방법이 보통이지만, 이 방법은 보통 수개월에서 수년으로 많은 시간이 소요된다. 따라서 최근의 연구는 주로 전위차를 이용하여 염화물이온의 이동을 전기적으로 촉진시켜 전기화학적 이론으로 해석하는 촉진 염화물 확산계수 평가 방법들이 주로 연구되고 있다. 따라서 본 연구에서는 다양한 촉진시험 방법 중 하나인 Tang 등의 방법을 이용하여 구한 염화물이온 확산계수와 인공해수 침지시험을 통하여 구한 농도차 염화물이온 확산계수와의 비교 평가를 실시하였다. 포틀랜드시멘트 콘크리트 및 고로슬래그미분말을 시멘트 질량의 40 및 60% 혼합한 고로슬래그미분말 혼합 콘크리트에 대하여 각각 물-결합재비 40, 45, 50 및 60%로 하여 촉진 염화물이온 침투깊이 및 염화물이온의 확산계수를 평가하였다. 염화물이온의 확산계수 및 침투깊이는 시멘트의 수화가 진행될수록, 물-결합재비가 작을수록 크게 감소하였다. 또한 시험 방법별 염화물이온 확산계수의 회귀분석 결과에 의하면, 촉진 및 침지시험으로부터 구한 염화물이온의 확산계수 사이에는 선형함수 형태의 상관관계가 있었으며 결정계수 0.96으로 좋은 상관성을 나타내었다. It is time-consuming to estimate chloride diffusivity of concrete by concentration difference test. For the reason chloride diffusivity of concrete is mainly tested by electrically accelerated method, which is accelerating the movement of chloride ion by potential difference. In this study, portland cement concrete and concrete containing with ground granulated blast-furnace slag (40 and 60% of cement by weight) with water-cementitious material ratio 40, 45, 50 and 60% were manufactured. To compare with chloride diffusivity calculated from the electrically accelerated test and immersed test in artifical seawater, chloride diffusivity tests were conducted. From the results of regression analysis, regression equation between accelerated chloride diffusivity and immersed chloride diffusivity was linear function. And the determinant coefficient was 0.96 for linear equation.
최두선(Doo-Sun Choi),제태진(Tae-Jin Je),서영호(Young Ho Seo),황경현(Kyung-Hyun Whang) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
In this paper, we presented reusable quartz master fabricated by electron-beam lithography and preliminary test of injection molding using suggested reusable quartz master. Conventional manufacturing technology of master can not recycle due to patterning with photoresist and is essential of a duplicate process that must manufacture the Father stamper and the Mother stamper. However, we have made it possible of the reusable master by directly patterning on quartz. We developed 100㎚-pit size reusable quartz master with intaglio carving patterns which is more fine size than those of DVD (400㎚) and blue-ray disc (200㎚). In the preliminary test of injection molding, we find optimum injection molding conditions using polypropylene.