Density and size-induced mixing and segregation in the FT4 powder rheometer: An experimental and numerical investigation

Segregation of granular materials is often induced by differences in size, density, shape and surface properties. Density and size-induced mixing and segregation of binary mixtures of glass beads and/or resin particles in the FT4 powder rheometer are investigated experimentally using a new FT4 methodology. The proposed methodol-ogy allows for quantification of mixing and segregation of components based on a mixing index. It is observed that the mixing index increases with increasing density and size ratio. Variation of flow energy and torque is re-lated to the mixing and segregation of the mixture components, thus demonstrating that the FT4 powder rheom-eter may be used as a predictive tool for the tendency of mixture components to segregate under various stress conditions. Numerical analysis by DEM shows that for non-cohesive systems mixing and segregation occur by sifting of fines through interstitial gaps formed between coarse particles in the dilated region. For the non-cohesive system, higher blade tip speeds reduce the rate of mixing and minimise the segregation of different-sized components. Increasing the interfacial energy reduces the rate of mixing and alleviates the segregation of particles. For the cohesive systems, mixing occurs by rupture of cohesive fine clusters with the mixing index in-creasing with increasing blade tip speed owing to the higher shear stresses that break the agglomerates. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study investigates mixing and segregation of binary mixtures of glass beads and/or resin particles based on density and size differences using a new FT4 methodology. Results show that the mixing index increases with density and size ratio, with flow energy and torque variation related to mixture components' mixing and segregation. DEM numerical analysis reveals that mixing and segregation occur differently in non-cohesive and cohesive systems under various stress conditions.