An investigation on the predictive capabilities of Discrete Element Method simulations of a powder mixing process in a laboratory scale paddle blade mixer is presented. The visco-elasto-plastic frictional adhesive DEM contact model of Thakur et al (2014) was used to represent the cohesive behaviour of an aluminosilicate powder in which the model parameters were determined using experimental flow energy measurements from the FT4 powder rheometer. DEM simulations of the mixing process using the contact model parameters were evaluated against the experimental measurements of the mixing rate. The results demonstrated that whilst the DEM model is capable of reproducing the FT4 flow energy of the powder to an excellent agreement, the simulations of the mixing process produced a qualitative agreement on the trend of the mixing rate in the experiments for both dry and wet powders. The mixing was underpredicted in the simulations, suggesting that flow energy measurements alone may not be sufficient for the optimization of a DEM model of powder mixing.

The handling of bulk solids in the form of powders is a fundamental process in a wide range of manufacturing industries, such as the automotive, aerospace, food, and healthcare sectors. All these sectors employ additive manufacturing (AM), as it enables the production of complex parts in a short amount of time. Thus, it is considered an established method for developing an agile manufacturing environment that can drastically reduce the lead time from conception to the production stage. At the same time, powder is a unique material sensitive to environmental and machine conditions; hence, establishing an optimal configuration is not straight-forward. This work presents a discrete element method (DEM) simulation of an experimental dosing system used in AM. We introduce a robust workflow that correlates suitable experimental data with simulation results, establishing models of real powders with different flowability. The results showed an excellent agreement between the experimental data and the simulation results and provided a better understanding of the material behavior. Furthermore, we employed a coarse-grained approach to extract continuum fields from the discrete data. The results showed that the cohesion level in the system was enough to create agglomerates that hindered the transport of the material and produced nonuniform distribution.

Current theories and design codes pertaining to storage structures for bulk solids have been developed in the context of rigid-walled silos, and may not be applicable for smaller and highly-flexible containers that are often used for industrial packaging and intermediate storage. The focus of this study is to investigate the effect of wall flexibility on the bulk stresses and wall pressures during storage using finite element analysis. The results show that when the wall stiffness is low, the computed bulk stresses in the vertical bin section are dominated by plasticity, whilst the stresses in the hopper section remain in the elastic state. In this situation the wall pressure in the bin section is heavily influenced by the strength of the stored solid, which controls the extent of plastic flow. Overall, the normal wall pressure in the bin section is found to decrease with wall flexibility leading to a corresponding increase in vertical stress in the stored solid. As a consequence, the stresses in the hopper also increase leading to increasing loads on the hopper walls and potential exacerbation of handling issues for cohesive materials in highly flexible containers.