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알루미늄 블랙 드로스로부터 산화 환원반응을 이용한 고순도 알파 알루미나의 제조
신의섭,안응모,이수정,오오츠키 치카라,김윤종,조성백,Shin, Eui-Sup,An, Eung-Mo,Lee, Su-Jeong,Ohtsuki, Chikara,Kim, Yun-Jong,Cho, Sung-Baek 한국재료학회 2012 한국재료학회지 Vol.22 No.9
We investigate the effects of redox reaction on preparation of high purity ${\alpha}$-alumina from selectively ground aluminum dross. Preparation procedure of the ${\alpha}$-alumina from the aluminum dross has four steps: i) selective crushing and grinding, ii) leaching process, iii) redox reaction, and iv) precipitation reaction under controlled pH. Aluminum dross supplied from a smelter was ground to separate metallic aluminum. After the separation, the recovered particles were treated with hydrochloric acid(HCl) to leach aluminum as aluminum chloride solution. Then, the aluminum chloride solution was applied to a redox reaction with hydrogen peroxide($H_2O_2$). The pH value of the solution was controlled by addition of ammonia to obtain aluminum hydroxide and to remove other impurities. Then, the obtained aluminum hydroxide was dried at $60^{\circ}C$ and heat-treated at $1300^{\circ}C$ to form ${\alpha}$-alumina. Aluminum dross was found to contain a complex mixture of aluminum metal, aluminum oxide, aluminum nitride, and spinel compounds. Regardless of introduction of the redox reaction, both of the sintered products are composed mainly of ${\alpha}$-alumina. There were fewer impurities in the solution subject to the redox reaction than there were in the solution that was not subject to the redox reaction. The impurities were precipitated by pH control with ammonia solution, and then removed. We can obtain aluminum hydroxide with high purity through control of pH after the redox reaction. Thus, pH control brings a synthesis of ${\alpha}$-alumina with fewer impurities after the redox reaction. Consequently, high purity ${\alpha}$-alumina from aluminum dross can be fabricated through the process by redox reaction.
열복사를 고려한 열기계학적 해석을 위한 유한요소 부영역 결합법의 적용
신의섭(Eui Sup Shin),진지만(Ji Man Jin) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
A finite element method based on the penalized subdomain-interface framework is proposed for fully-coupled, nonlinear thermomechanical analyses with thermal contact and/or radiation boundaries. In the variational formulation, a penalty functional scheme is adopted for connecting subdomains and interfaces that satisfy continuity requirements. As a consequence, the domain can be arbitrarily divided to independently- modeled subdomains without considering the conformity of meshes. Since nonlinearities due to the radiation boundaries can be localized in a few subdomains, the computational efficiency is increased with appropriate algorithms. By solving numerical problems, these advantageous characteristics are confirmed carefully.
잔류응력을 고려한 원통형 복합재 튜브의 해석 및 최적 설계
신의섭(Eui Sup Shin) 한국항공우주학회 2004 韓國航空宇宙學會誌 Vol.32 No.1
복합재료 성형 과정에서 발생하는 잔류응력의 효과를 고려한 원통형 튜브의 해석 및 최적 설계 문제를 취급하였다 준정적 열탄성 이론에 근거한 해석적인 기법을 이용하여 두꺼운 벽을 갖는 적충 복합재 튜브의 웅력 분포를 계산하였다. 실제 축대칭 하중을 받는 복합재 튜브의 강도 관련 성능을 향상시키기 위하여, 응력 성분에서 산출되는 파손 지수를 최소화하는 최적 설계 문제를 설정하였다. 직교 적충 구성에 대한 계산 결과, 층 두께를 조절함으로써 잔류응력을 일정 수준으로 감소시킬 수 있음을 확인하였다. 또한, 적충 각도와 순서, 전체 두께, 축대칭 하중이 최적화 결과에 미치는 영향에 대해서 면밀히 고찰하였다. This paper deals with the analysis and optimum design of cylindrical composite tubes considering process-induced residual stresses. The thermomechanical stresses in the thick-walled multi-layered composite tubes are calculated with an analytical model based on quasi-static thermoelasticity. An optimum design problem is then presented to improve the strength-related performance of the cylindrical composite tubes subject to axisymmetric external loads as well as to residual stresses. The numerical results show that, in the case of cross-ply tubes, the residual stresses can be reduced to a certain level by controlling ply thicknesses. In addition, the effects of ply orientation, stacking sequence, wall thickness, etc. are carefully examined.
영역/경계 분할법을 적용한 기계적 삭마 과정의 열구조 연계 해석
신의섭(Eui Sup Shin),김성준(Sung Jun Kim),김종일(Jong Il Kim) 한국항공우주학회 2011 韓國航空宇宙學會誌 Vol.39 No.1
이차원 구조물의 열응력 및 기계적 삭마 과정 해석을 위하여 영역/경계 분할법에 근거한 유한요소법을 적용하여 열구조 연계 정식화를 수행하였다. 삭마 재료 거동의 온도 의존성과 열분해 반응으로 인한 재료 비선형성 및 열복사와 같은 비선형 경계 조건을 일부 부영역과 공유면에 한정할 수 있다. 문제를 단순화하기 위해 열화학적 삭마 효과는 고려하지 않았으며, 기계적 삭마에 따른 표면 후퇴 판정 기준으로 열응력 해석을 통한 최대면내 전단 응력을 선택하였다. 간단한 수치 실험을 수행하여 제안된 기법의 신뢰성에 대한 분석과 기계적 삭마 과정의 기본적인 경향을 파악하였다. A coupled thermal/structural analysis of mechanical ablation is performed based on domain/boundary decomposition and finite element method. The ablative material non -linearity and boundary non-linearity can be easily localized within a few subdomains and/ or on the boundary interfaces. An enthalpy method is applied to simplify the effect of heat of pyrolysis in the ablative subdomains. In addition, maximum in-plane shear stress is considered as a surface recession criterion for the mechanical ablation simulation. The basic characteristics of the proposed method are examined carefully through numerical experiments.