Experimental Investigation of Shear-Induced Particle Migration in Steady-State Isothermic Extrusion

Abstract

Experimental evidence for radial particle migration in a pressure driven tube flow of a non-Newtonian viscous concentrated suspension will be presented. The suspension is a well-characterized, mono-modal nickel spherical particles having 30% volume fraction. The particles experienced a drift particle concentration profile as a function of the radial position. SEM technique was used to capture micrographs of the sample at various sections in the axial flow direction with a specially designed capillary split die. With the help of image analytical software, the distribution of particle concentration as a function of radial position was obtained. Finally, comparisons were made between experimental results and numerical predictions based on a continuum diffusive-flux model for shear-induced particle migration. Good agreement between experimental observations and numerical predictions indicated that the procedures were useful in capturing particle migration in steady-state isothermic extrusion flow which exhibits a near plug-like concentration profile.

Shear-induced particle migration modelling in a concentrated suspension flow

“…Although the value of φ c could be adjusted, it is normally assumed to be a constant for a particular powder-binder system. For this investigation, φ c was assumed to be 0.68 for a pressure-driven tube flow [20]. For the determination of the material constant m in equation ( 9), it is important to carry out experiments under conditions of minimal or no particle migration.…”

“…As it was shown Table 1. Physical and rheological parameters of binder and powder system [20]. (10) eqn ( 10) eqn ( 10) eqn ( 10) eqn ( 14) eqn ( 9) eqn ( 9 [12] that a parallel-plate viscometer introduced little migration, m was determined to be 0.82 using this testing method.…”