Effective mass of powder beds subjected to low magnitude vibration and its application to binary systems: Part 2 - Comparison of segregated and well-mixed binary powder mixtures

This paper presents an investigation of segregated and well-mixed binary powder mixtures in terms of the effective mass of the powder beds, when subject to low magnitude vibration (< 0.1 g). An experimental system, developed in Part 1 of the present series of papers, was used to measure the effective mass of powder beds. Segregated systems were produced from materials of different densities, by layering materials. Tests were performed with both segregated and well-mixed systems with changing the mixing ratio. There was a significant difference in the effective mass between segregated and well-mixed systems, indicating that the effective mass of binary powder mixtures is dependent upon the dispersion of composition and the quality of mixing. The effective mass of well-mixed systems was in agreement with Rayleigh's theory, whilst the segregated systems showed significant deviations from the theory. A simplified model based upon Rayleigh's energy method was proposed to predict effective mass for segregated systems, and compared to experimental data. Results showed a reasonable agreement between the model and experimental data. The application of this technology to mixing has been examined, and the effective mass has been measured as a function of mixing time in a number of mixing situations. The effective mass indicates not only the deviation from an ideal mix, but also the direction of segregation.