عنوان

تحلیل میدانهای دو بعدی دما و سرعت در انجماد آلومینیم با استفاده از روش المان مرزی

شماره

‭۵۶۷۴پ‬

زبان متن نوشتاري يا گفتاري و مانند آن

per

عنوان اصلي

تحلیل میدانهای دو بعدی دما و سرعت در انجماد آلومینیم با استفاده از روش المان مرزی

نام نخستين پديدآور

/فرامرز طلعتی کلاسر

نام ناشر، پخش کننده و غيره

دانشگاه تبریز: دانشکده فنی مهندسی مکانیک، گروه مهندسی مکانیک

متن يادداشت

چاپی

متن يادداشت

فاقداطلاعات کامل

جزئيات پايان نامه و نوع درجه آن

دکترا

نظم درجات

مهندسی مکانیک تبدیل انرژی

زمان اعطا مدرک

‮‭۱۳۸۲/۰۶/۲۵‬

کسي که مدرک را اعطا کرده

دانشگاه تبریز: دانشکده فنی مهندسی مکانیک، گروه مهندسی مکانیک

متن يادداشت

.‮‭the boundary of the domain is not fixed. These problems are called moving boundary problems (MBP). The location and the velocity of the interface are not known in these problems and finding them are a part of solution. Melting and solidification of metals, which is back- bone of today's industry, belong to this class of problems. The determination of temperature distribution, position of the interface and the velocity of the interface in solidification of metals are very important. Micro- structure and mechanical properties of metals and alloys are directly related to the heat transfer rate during their solidification and manufacturing. Analytic solutions can be obtained for a few phase change problems. These solutions are limited to the specified conditions, which are not applicable in real world. So, we use approximate methods to solve phase change problems, among them are Finite Difference Method (FDM), Finite Element Method (FEM) and Boundary Element Method (BEM). In BEM, the approximate values of unknown quantity and its derivatives are used on the boundary and one reduces the dimensionality of the problem. This method has attracted the interests of many researchers during last three decades. It is believed that it is one of the most suitable methods for the analysis of moving boundary problems. In this work, we have used the BEM with constant element, linear element and quadratic element with time dependent Green's function to analyze the solidification of pure Aluminum. In order to compare the different results, experiments were carried out, using the facilities of the school of material and metallurgy of the University of Birmingham, UK. The selected model was a ۱۰۰ x۱۰۰ x ۲۰mm plate, insulated with Fiberfrax insulating material on some boundaries to create different boundary conditions. Thermal analysis was carried out using K-type thermocouples, a nickel-chromium/nickel aluminum conductor combination. Thermocouples were located along the centerline of the casting at different distances from one another. The diameter of thermocouple wire was ۰.۳ mm and crossing the wire and spot welding created the junction. The excess wire was trimmed off. The wire (with the exception of approximately ۱ mm distance from the junction tip) was insulated with white paint (TiO۲- containing emulsion paint and subsequently fired to burn off volatiles) to prevent the possibility of a short circuit by the liquid metal. An effective internal calibration of the thermocouples was performed taking advantage of the fact that pure Aluminum was being frozen, thus defining a temperature close to ۶۵۹.۰ , Thus thermocouple readings were adjusted to read about ۶۵۹.۰ , during the early part of the plateau region of the cooling curve. Data were logged into a computer at rates of selected from ۱۰,۲۰,۵۰,۱۰۰,۲۰۰,۲۵۰ signals per second for different experiments. Different boundary conditions were created during the experiment. In one experiment the front face was maintained at constant temperature by the application of a jet of compressed air to the back of mould. In another experiment ensuring that the back of the mould was in relatively still air used convection boundary condition. Cooling curves and derivative first curves were used to identify the end of solidification process. The distance between thermocouples is known, one may read the elapsed time from time axis, to calculate the velocity of freezing front. A rapid drop in temperature was recorded at points very near to the mould surface (implying that rate of solidification is initially high and becomes smaller at large times). As distance from the mould surface increases, temperature gradient decrease. The problem under consideration was also analyzed using the MAGMA software. The results show good agreement between two numerical methods, namely, the BEM results and the MAGMA results.It can be said that BEM is a successful method in the field of moving boundary problems. Formulation in this method is of the mixed type (the unknown quantity and its derivatives appear in the formulation), so; the accuracy of the method is better than other methods. Data preparation is simpler and it takes less time compared to other numerical methods. Adjustment of the data is simple۵‬ ‮‭Mathematical modeling of most physical phenomena in nature yields differential equations or integral equations. All of the governing equations in engineering science and physics have not analytic solutions or closed form solutions. The boundary of the problem under consideration is fixed in classic problems. Combination of non-linearity of equations and complicated geometry of domain and boundary lead to considerable reduction of analytic solutions. In some problems, such as phase change, manufacturing of crystals, chemical reactions, corrosion of metals, flow of fluids in a porous media, arc welding‬

مستند نام اشخاص تاييد نشده

طلعتی کلاسر، فرامرز

مستند نام اشخاص تاييد نشده

خوشروان آذر، اسماعیل، استادراهنما

مستند نام اشخاص تاييد نشده

اسماعیل زاده، اسماعیل، استادمشاور

مستند نام اشخاص تاييد نشده

علوی تبریزی، سید پرویز، استادمشاور

مستند نام اشخاص تاييد نشده

ا کرمی، قدرت، استادمشاور

وضعیت فهرست نویسی

نمایه‌سازی قبلی