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Item type:Publication, Access status: without files , Application of micro computed tomography for adjustment of model parameters for discrete element methodNowadays the Discrete Element Method (DEM) is widely applied for the numerical simulation of granular materials. However, for the effective application of DEM detailed information about material properties is needed. Some material parameters of individual particles can be directly measured using various experimental set-ups like shear cell, compression tester, electron microscopy, etc. Nevertheless, in the majority of cases such measurements do not suffice to get overall information about the material. Therefore, various macroscopic experiments like determination of static or dynamic angle of repose are often used to validate DEM simulations and to adjust model parameters. In this contribution, an alternative non-intrusive technique for the estimation of unknown parameters, which is based on particle tracking in sets of the micro computed tomography images, is proposed. In comparison to other methods this technique allows to obtain detailed information about particle motion inside the granular material and does not only rely on the surface properties. In the presented contribution experiments and simulation studies were performed using a cylindrical mixer apparatus filled with polyethylene microspheres. Based on the analysis of obtained images, the exact 3D-positions of all particles in the mixing volume were determined and extracted. For numerical calculations the DEM implemented into component-based simulation framework MUSEN was used.Publicationtype: Journal Article151 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , DEM simulations of amorphous irregular shaped micrometer-sized titania agglomerates at compression(2015-05-01); ; ; ; Bulk solids are exposed to time-dependent mechanical stressing due to particle-particle and particle-apparatus contact interactions during various manufacturing processes and transportation steps. These interactions can be described by discrete element method (DEM) based on the contact models of particles. Usually in DEM simulations the particles are assumed to be spheres and as a consequence shape effects are neglected. However, most bulk solids processed in industry consist of irregular shaped particles. Therefore, in order to improve accuracy of numerical simulation the real shapes of particles must be considered in DEM. In this work, amorphous irregular shaped micrometer-sized titanium dioxide agglomerates were investigated. The force-displacement curves at compression were obtained with the help of a self-designed experimental setup. Based on the experimental data, several material parameters were determined and implemented in viscoelastic and elastic-plastic contact models. To consider the shape effect in the estimation of contact parameters the DEM simulation of studied agglomerates was performed by multi-sphere approach and bonded-particle model. The shape and position of the agglomerates on the loading pin were obtained by X-ray computer tomography and used in DEM simulations. From the obtained results it was pointed out that the bonded-particle model based on Maxwell viscoelastic model gives the best agreement with experimental data from compression tests with titania agglomerates.Publicationtype: Journal Article57 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Contact models based on experimental characterization of irregular shaped, micrometer-sized particlesThe goal of this study is to investigate experimentally the mechanical contact properties of fine particles (<120μ m) using of a novel experimental setup. On the basis of deformation curves from compression tests, particle behaviour under mechanical stress can be approximated with theoretical contact models. Models examined in this study include Walton and Braun, Tomas and Antonyuk, Zener and Thornton. Influence of climatic conditions on particle behaviour as well as hardening effects related to cyclic loading were also considered. Maltodextrin was used as a model substance for primary particles, while irregular shaped titanium dioxide granules were used to study the behaviour of agglomerates. In both cases, results are in good agreement with the established theories.Publicationtype: Journal Article64