Abstract
The analysis is carried out and the presence of a zone of a piston flow, which has a significant influence both on the process of extrusion, and on the determination of the discharge-pressure characteristics of the screw, is established. It is noted that the effective viscosity has a physical meaning if the shear rate to which it corresponds is indicated. The effective viscosity is considered to consist of two components: the plastic viscosity corresponding to the viscosity of the Newtonian fluid and the structural viscosity that characterizes the shear resistance caused by the tendency of the solid particles contained in the Bingham liquid to form a structure. The effective viscosity is introduced into many hydrodynamic equations if the shear rate to which it corresponds is known. In the auger channel there are zones of forced flow created by the dynamic shear stress and the reverse flow of the head resistance created by the overpressure. The shear rate in the auger channel is marked by considerable heterogeneity and determines the complex nature of the shear deformation of the material during extrusion. Regardless of the pressure amplitude, the rigid core can not completely disappear, because for very small dimensions of the nucleus the pressure value must be very large, and with the disappearance of the plastic flow it must become infinite. Thus, the dependence of the shear stress on the shear rate for the flow of a Bingham viscoplastic fluid is always nonlinear for any values of the shear rate. An important element in the calculation of the discharge-pressure characteristics of the extrusion process is the localization of the plastic flow in the screw channel. As a result of the analysis of the model of the layered flow of viscoplastic Bingham liquid in the extruder channel, it is established that there is a zone of piston flow that exerts a significant influence both on the process of extrusion and on the determination of the discharge and pressure characteristics of the screw.
Highlights
WZ, сительно середины канала по оси Y рассмотрим которое получаем подстановкой найденной одномерное уравнение при ус = b/2течения в рамках бингамовской реологической модели координаты xo из уравнения (10)
В результате проведенного анализа модели слоистого течения вязкопластичной бингамовской жидкости в канале экструдера
Summary
Модель слоистого течения вязкопластичной Бингамовской жидкости в канале экструдера // Вестник ВГУИТ. Где τ – напряжение сдвига; τo – напряжение, необходимое для начала течения жидкости; μ p – пластическая вязкость, которая определяется как касательное напряжение, превышающее предельное сдвиговое значение и сообщающее жидкости единичную скорость сдвига; dv (r ) – Следовательно, ламинарное течение вязкопластичной бингамовской жидкости определяется уравнением: μ p=
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