The Flow Of The Powder Particles Clogging The Behavior Of Sub-poly

Powders/granular matter, one kind of soft matter, is different from conventional solid, liquid and gas, also considered to be complex fluids. New theories and approaches are needed to investigate and understand the granular matter. As we known, the yield and flow, jamming and segregation of powders are closely related to the powder metallurgy processes such as mixing, discharging and charging of powders.In order to prove up the granular flowability, jamming properties, and segregation mechanism of granular mixture including the main influenced factors, this paper focuses on investigating the flow of granular matters with different sizes and shapes in rotating drum, the jamming of spherical granular matter pouring out through a conical shape bottleneck, and also the segregation of granular mixture both in the drum and the heap flow equipment. The results suggest:(1) The physical properties of granular matter are related to their states, the characterize of granular flowability should both reflect the granular physical properties and the flowing states. Granular shear rate strongly reflect the resistance to external shearing or the ability of keeping the flowing state. According to the linear change of the speed of flowing layer under the low rotating speed of the drum, we have measured the thickness of the flowing layer, and proposed that deformation time Tγ=1/{ω[(R/h)2-1]} can be used to describe the flowability of granular matter. This method is simple and reliant, and the results are in good agreement with the data getting from the hopper test. The obvious increase of the cohesion force between different grains is caused by the existence of liquid, leading to abrupt change of evolution of microstructure and flowing state of granular system during shearing deformation, which may be the fundamental cause to the fast change of physical properties of powders and granular matter.(2) The jamming of granular flows which is closely related to the flowing modes is depended on the flowability of granular matter. There are four flowing modes when grains flow through a particular bottleneck, and the interaction of different grain flowing modes is the main mechanism of jamming and the effect of bottleneck; The distribution of the discharging grain numbers are exhibited as a single-peak function: with the increase of grain surface frictional coefficients and density of granular matter, the peaks are reduced and the average avalanche sizes are increased.(3) The segregation of granular mixtures are determined not only by the physical discrepancy of different grains, but also by the granular flux Q and the additive volume of liquid W. Segregation will disappear as Q or W reaches a certain critical value. For example, when granular mixtures with the granular size ratio 3 were poured, segregation would disappear as Q reached 31.25ml/s or W reached 0.7%. Thus, by reducing the discrepancy of granular physical properties, enhancing Q or W, the segregation of granular mixtures can be prevented during the pouring and flowing processes.Much more work is still needed to couple different factors to quantitatively analyze the influence on the segregation of granular mixture.