Experimental Study On The Densification Of Binary Sphere Packing Subjected To 1D And 3D Vibrations

In this thesis, systematically physical experiments were carried out to study the packing densification of binary steel-ball bearing mixture subjected to one-dimensional (1D) and three-dimensional (3D) continuous vibrations and total feeding. The influence of vibration parameters such as vibration frequency co, the volume fraction of large particles XL, the size ratio of small particle versus large particle r and the container size D (Diameter) on particle packing density was studied and analyzed. Besides the realization of densest packing structure with different packing conditions, the corresponding optimal processing parameters and their role in vibrated packing densification are also compared and analyzed. Following results can be indicated:(1) No matter in 1D vibrated packing or in 3D vibrated packing, the vibration frequency co plays the silimar role in the process of packing densification for binary steel-ball bearing mixture, i.e. the packing density of binary steel-ball bearing mixture increases with co to a maximum and then decreases with the further increase of co. On other words, there is an optimum value forωto achieve the maximum packing density in 1D or 3D vibrated packing, too large or too small co will be not good for densification. In this study, the optimum frequencys areω=130 Rad/s andω=110 Rad/s to realize the densest packings for 1D and 3D vibrations, respectively.(2) With the two vibrated modes, the volume fraction of large particles XL also has the same influence as that of vibration frequency co on the packing density of binary steel-ball bearing mixture. I.e. the packing density first increases with the XL and then decreases. There is an optimum value XL* to obtain the densest packing at each condition. Here, XL* equals to about 0.7 for both 1D and 3D vibrated packing, which implies that the volume fraction of large particles is in dominant, this is in good agreement with others'numerical results.(3) The size ratio of small particle versus large particle, r, is also an important factor in the packing densifiction of binary mixtures under the two vibrations. In this work, four different size ratios are used to study their effects on packing density. It can be identified that with other parameters fixed, the smaller the size ratio r, the larger the packing density can be realized. In our experiments, the maximum packing density corresponds to r=0.0654.(4) In order to eliminate container size or container wall effects, we used five different sized containers to carry out the physical experiments. The results indicate that the larger the container size, the less the wall effect, and the higher the packing density. Through the extrapolation on the packing densities in five containers, we found that the maximum packing density in infinite sized container can reach 0.8294 and 0.8809 for 1D and 3D vibration, respectively, which are much lager than the largest value of 0.74 for mono-sized sphere packing subjected to vibration.(5) Through the comparion and analysis on the packing densificaton of binary steel-ball bearing mixtures under two vibration modes, we find that the optimal processing parameters to realize the densest packings are:1D vibration,ω=130rad/s, XL=0.7 and r=0.0654; 3D vibration,ω=110rad/s,XL=0.7 and r=0.0654.The results from the packing densification of binary steel ball bearing mixtures under 1D and 3D vibrations can, on one hand, provide the researchers with the new idea to realize the higher packing density, on the other hand, the dense packing structure obtained in our physical experiments can validate the numerical results, which is very meaningful in both the theoretical study and real application.