Direct laser sintering of a mixture of two metal powders with significantly different melting points is investigated by numerical simulation. The model is based on self-consistent non-linear continuity equations for volume fractions of components and on energy transfer equations for the powder mixture. It includes the movement of the solid particles due to shrinkage because of the density change of the powder mixture and the liquid flow driven by the capillary and gravity forces. The liquid flow is determined by Darcy's law. The effect of surface settlement of the powder is obtained. The width increasing rate of the melting zone depend both on the parameters of the laser radiation (on the power of the beam) and on the physical parameters of the particle's material, and it increases with the increasing of the penetrability or the increasing of the phase-transition heat. The increasing of the laser power under other factors being equal results in the acceleration of the melting front propagation.
О р д е н а Л е н и н а ИНСТИТУТ ПРИКЛАДНОЙ МАТЕМАТИКИ имени М.В.Келдыша Р о с с и й с к о й а к а д е м и и н а у к Ю.А. Повещенко, В.О. Подрыга, Ю.С. Шарова Интегрально-согласованные методы расчета самогравитирующих и магнитогидродинамических явлений Москва-2018 Повещенко Ю.А., Подрыга В.О., Шарова Ю.С. Интегрально-согласованные методы расчета самогравитирующих и магнитогидродинамических явлений Одним из направлений вычислительной астрофизики является разработка численных методик для моделирования самогравитирующих объектов. К ним относятся протопланетные облака, сверхновые звезды и другие скопления больших масс веществ, в эволюции которых существенную роль играет гравитация. Дискретное моделирование в этих задачах при значительных перепадах плотностей и возникновении, например, подвижных, адаптивных, неравномерных сеток может приводить к заметным нарушениям баланса гравитационной энергии. Данная работа посвящена построению полностью консервативных разностных схем в части интегрально-согласованных расчетов, воздействующих на среду гравитационных и магнитогидродинамических сил в лагранжевых переменных.
With the recent Supernova 1987a in the LMC, new and interesting possibilities have arisen for the solution of a problem relating to the explosion mechanism of supernovae. The presupernova was probably a B3Ia, the blue supergiant, and not a red giant as it was earlier thought likely. Calculations of the evolution, which have been made recently, show that the loss of hydrodynamical stability may be connected with carbon burning in the stellar core during the blue giant stage. This loss of stability of the CO core is the main factor in our explanation of the recent event of SN 1987a.Before we consider the thermonuclear model of a supernova based on a thermal flash in the degenerate CO core, let us dwell on the present situation in the theory of supernovae. The main problem in supernova theory is the simultaneity of births of a compact remnant and an expelled envelope. The compact remnant later becomes a neutron star. The expelled envelope determines the curve of brightness. Now, it is clear that a supernova explosion may result in either the total disruption of a star or in the simultaneous production of a compact remnant and an expelled envelope.
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