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TV 유리의 반복 성형공정에서 금형 열사이클 해석을 위한 효과적 방법
최주호,김준범,황정해,하덕식,Choi, Joo-Ho,Kim, Jun-Bum,Hwang, Jung-Hea,Ha, Duk-Sik 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.9
An efficient method is developed for plunger thermal cycle analysis in repeated forming process of the TV glass. The plunger undergoes temperature fluctuation during a cycle due to the repeated contact and separation from the glass, which attains a cyclic steady state having same temperature history at every cycle. Straightforward analysis of this problem brings about more than 80 cycles to get reasonable solution, and yet hard to setup stopping criteria due to extremely slow convergence. An exponential fitting method is proposed to overcome the difficulty, which finds exponential function to best approximate temperature values of 3 consecutive cycles, and new cycle is restarted with the fitted value at infinite time. Numerical implementation shows that it reduces the number of cycles dramatically to only 6-18 cycles to reach convergence within 10 accuracy. A system for the analysis is constructed, in which the thermal analysis is performed by commercial software ANSYS, and the fitting of the result is done by IMSL library. From the parametric studies, one reveals some important facts that although the plunger cooling or the glass thickness is increased, its counter part in contact is not much affected, duo to the low thermal conductance of the glass.
지석만,최주호,김준범,하덕식 한국 항공대학교 항공산업기술연구소 2001 航空宇宙産業技術硏究所 硏究誌 Vol.11 No.-
This paper addresses a method for numerical simulation in the pressing process of hot glass. Updated Lagrangian finite element formulations are employed for the flow and energy equations to accommodate moving meshes. The model is assumed axi-symmetric and creep flow is assumed due to the high viscosity. Commercial software ANSYS is used to solve the coupled flow and energy equations. Moving contact points as well as free surface during the pressing are effectively calculated and updated by utilizing API functions of CAD software Unigraphics. The mesh distortion problem near the wall is overcome by automatic remeshing, and the temperatures of the new mesh are conveniently interpolated by using a unique function of ANSYS. The developed model is applied to the pressing process of TV glasses. In conclusion, the presented method shows that the pressing process accompanying moving boundary can be simulated by effectively combining general purpose softwares without resorting to special dedicated codes.
CAD와 유한요소해석을 연계한 금형 냉각문제의 설계최적화에 관한 연구
오동길,류동화,최주호,김준범,하덕식 한국 항공대학교 항공산업기술연구소 2001 航空宇宙産業技術硏究所 硏究誌 Vol.11 No.-
In mechanical design, optimization procedures have mostly been implemented solely by the CAE codes combined by optimization routine, in which the model is built analyzed and optimized. In case of complex geometries, however, CAD is indispensable tool for the efficient and accurate modeling. This paper presents a method to carry out optimization, in which CAD and CAE are used for modeling and analysis respectively and integrated in an optimization routine. Application Programming Interface(API) function is exploited to automate CAD modeling, which enables direct access to CAD. The advantage of this method is that the user can create very complex object in parametric and automated way, which is impossible in CAE codes. Unigraphics and ANSYS are adopted as CAD and CAE tools. In ANSYS, automated analysis is done using codes made by a script language, APDL(Ansys Parametric Design Language). Optimization is conducted by VisualDOC and IDESIGN respectively. As an illustrative example, a mold design problem is studied, which is to minimize temperature deviation over a diagonal line of the surface of the mold in contact with hot glass.
최적화 기법과 분산 컴퓨팅을 이용한 재료 성형공정의 역문제 에 관한 연구
최주호(JooHo Choi),오동길(DongGil Oh),하덕식(DukSik Ha),김준범(JunBum Kim) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
In this paper, an inverse problem of glass forming process is studied to determine a number of unknown<br/> heat transfer coefficients which are imposed as boundary conditions. An analysis program for transient heat<br/> conduction of axi-symmetric dimension is developed to simulate the forming and cooling process. The<br/> analysis is repeated until it attains periodic state, which requires at least 30 cycles of iteration. Measurements<br/> are made for the temperatures at several available time and positions of glass and moulds in operation. Heat<br/> removal by the cooling water from the plunger is also recorded. An optimization problem is formulated to<br/> determine heat transfer coefficients which minimize the difference between the measured data and analysis<br/> results. Significant time savings are achieved in finite difference based sensitivity computation during the<br/> optimization by employing distributed computing technique. The analysis results by the optimum heat transfer<br/> coefficients are found to agree well with the measured data.