Numerical Simulation And Experimental Study On The Vibrated Packing Densification Of Regular Icosahedral Particles

In this thesis,the packing densification of regular icosahedral particles under mechanical vibrations was systematically studied.The regular icosahedra are typical non-spherical particles,which is one of the five Platonic solids.In particle packing area,much less work was conducted to investigate the packing of icosahedral particles,while their dense packing structures are really important for scientific research.Therefore,the packing densification of regular icosahedral particles under three-dimensional(3D)mechanical vibrations was systematically and comprehensively researched in both physical experiments and numerical simulations.Emphases were mainly focusing on the effects of the vibration parameters,characterization on macro-and various microscopic properties,and densification mechanism analysis.In physical experiments,the work was mainly carried out based on the packing densification of regular icosahedral particles under 3D mechanical vibrations.By using continuous vibration and total feeding,the effects of various vibration parameters(such as vibration time t,amplitude A,vibration frequency ?,and vibration intensity ?)and container size D on the packing densification of icosahedral particles were systematically studied.The results show that the packing density first increases with the amplitude A and vibration frequency ? to a maximum and then decreases with the further increase of A and co.Under final optimal vibration conditions,the maximum packing density of the regular icosahedral particles after extrapolation can reach 0.7147.In numerical simulations,the packing densification process in physical experiments was reproduced by 3D modelling using discrete element method(DEM).In addition to the systematic investigations on the influences of vibration conditions and container size on the particle packing densification.two important packing structures have been obtained,i.e.random loose packing(RLP)and random close packing(RCP).Besides the characterization on the macroscopic properties of these two structures,more emphases were focusing on quantitative characterization and analysis of their microscopic properties such as coordination number(CN),radial distribution function(RDF),particle contact type,particle orientation distributions,and stresses/forces etc.The results indicate that by properly controlling the vibration conditions,the transition of regular icosahedral particle packing from RLP to RCP can be realized.Through extrapolation,the maximum packing density obtained can reach 0.7078,which is much comparable with the result from physical experiments,implying the reliability of the numerical models used in the DEM simulations.Microscopic analyses indicate that the average CN in RCP structure after vibration increases.Two obvious peaks can be observed in RDF curve for RLP and three can be identified for RCP.From RLP to RCP,the probability of face-face contacts between particles increases,while that for edge-edge,edge-face,and face-vertex contacts decreases.The randomness of the obtained loose and dense packings has been proved by orientation correlation function.And it is also found from the research that the force and stress distributions are more uniform in RCP structure than in RLP structure.