Experimental Study On The Packing Densification Of Cylindrical Particles Subjected To1d And3D Vibrations

In this thesis, systematically physical experiments were carried out to study the packing densification of cylindrical particles subjected to one-dimensional (ID) and three-dimensional (3D) vibrations. By adopting total feeding in1D and3D continuous vibrations, we systematically studied the influence of vibration parameters such as vibration tine t, amplitude A, frequency ω, and vibration intensity Γ (Defined as Γ=Aco2/g, where g is gravity acceleration), container size (wall effect), aspect ratio and sphericity of cylindrical particles on particle packing densification. Meanwhile, the experimental results were used to verify the analytical model which was proposed to predict the random packing density of cylinders. Following results can be indicated:No matter in1D or in3D vibrated packing, the packing density of cylinders increases gradually with vibration time to a maximal value and then tends to be constant. Also, the influence of vibration amplitude A and frequency ω on the packing density of cylinders in1D and3D vibration conditions has similar trends. In other words, in both case the packing density of the cylinders first increases with amplitude or frequency to a maximal value and then decreases with further increase of A or co. The influence of A or ω can be ascribed to the vibration intensity Γ effect; increasing A or ω can lead to the increase of Γ, which will then increase the packing density. When the packing density reaches the maximum value, it will decrease with the further increase of Γ. The results indicated that different A and ω combinations can lead to the same Γ, however, the corresponding packing densities are quite different; On the other hand, the same packing densities can also be obtained by different Γ, which means that packing densification can’t be characterized by simply using a single parameter Γ. A and ω should be considered separately.The packing density of cylinders increases with the aspect ratio (l/d) or sphericity to a maximum and decreases, in our physical experiments, the densest random packing structure can be readily realized at the aspect ratio of l/d=1.The influence of container size on the packing density can be ascribed to the container wall effect. When other experimental conditions are fixed, the greater the container size, the higher the packing density. Through the extrapolation on the packing densities in different sized containers, the container size effect can be eliminated.The optimum process parameters for the densest packing structures in our physical experiments are given as following (l/d=1):(1)1D vibration:vibration frequency ω=130Rad/s, amplitude A=0.35mm, the extrapolated maximum random packing density can reach ρmax=0.719;(2)3D vibration:vibration frequency ω=80Rad/s, amplitude A=0.35mm, the extrapolated maximum random packing density can reach ρmax=0.730.The results for the cylindrical particle packings are much comparable with those predicted by the proposed analytical model, which proves that the proposed analytical modelis very effective in predicting the random packing density of cylinders.