Experimental Study On Dense Packing Of Monosized And Binary Spherical Particles Subjected To Vibrations

In this thesis, the densification of mono-sized particle packing under two-dimensional (2D) continuous vibrations corresponding to total feeding and batch-wise feeding is systematically studied physically, where the effects of vibration parameters (such as vibration time t, amplitude A, vibration frequencyω, vibration intensityΓ), container size D (wall effect), and batch of feeding B on packing density, and the optimal processing parameters which realize the densest packing are determined as well. Meanwhile, the physical experiments on binary packing of particles under one-dimensional (1D) continuous vibrations were initially carried out, which focusing on the effects of particle size ratio and composition on packing density. The results indicate that:(1) 2D continuous vibration and total feeding can realize much denser packing than 1D vibration, the maximum packing density for mono-sized glass beads in infinite container (to eliminate the wall effect) can reach 0.6757, which indicates that the formed structure is not purely random any more, and partial ordering is observed experimentally.(2) Vibration time t can speed up the densification, however, too long t will not further increase the packing density.(3) No matter total feeding or batch-wise feeding, the effects of frequencyωand amplitude A on packing densityρall have the same trends, i.e. p firstly increases with A or co to a maximum and then decreases with further increasing A or co. Therefore, in each case there exists optimalωand A to realize the dense packing.(4) The effects of A andωon packing density can be ascribed to the role of vibration intensityΓ(defined as F=Aω2/g), increasing A orωcan result in the increase ofΓ, consequently, the input energy to the packing increases as well, which is helpful for the densification. However, too large A orωwill cause too much energy input to the packing, which creates over excitation on the packing and gets the loose packing. Therefore, the choice ofΓshould be controlled to a certain extent. In addition, through analysis we find that we should not simply use a single parameterΓto characterize the obtained dense packing structure. Alternatively, A andωshould be considered separately.(5) Besides the vibration parameters, the container size which reflects the wall effects can also influence the packing density. Normally, the larger the container size, the less the wall effects, and the denser the particle packing will be. Actually, through the extrapolation on packing density in different sized containers we can eliminate the wall effects. The results show that through density extrapolation, the maximum packing in infinite sized containers in total feeding and batch-wise feeding conditions can reach 0.6757 and 0.7131, respectively. The densities are much higher than the maximum value 0.64 of random close packing, which indicates the transition of packing structure from random to order.(6) For the case of 2D vibration and batch-wise feeding, experiments indicate that the batch of feeding B can also creates important effects on packing density. When B is between one layer/batch and three layers/batch, the effects are much obvious, i.e. corresponding to the same vibration conditions, the packing density decreases sharply with the increase of B. When B is more than three layers/batch, its effects can be ignored by further increasing its value, here the corresponding packing density is already much low. When B≤1 layer/batch, high packing density can be realized, in this area the packing density will not change much with the variation of B.(7) In the binary packing of two different sized particles under 1D continuous vibrations, the size ratio and composition (volume fraction occupied by large particles) of particles can create important effects on packing density when the vibration conditions are fixed. Generally, the larger the size ratio, the denser the packing density will be within the same conditions; Meanwhile, for composition effects, the packing density will firstly increase to a maximum value with the increase of the composition and then decrease with the further increase of the composition. Additionally, the and then decrease with the further increase of the composition. Additionally, the maximum packing density corresponds to the large amount of large particles. And the larger the particle size ratio, the larger the composition of large particle will occupy, which is in satisfactory agreement with Furnas' law. The results show that even though in finite sized container (D=229.70mm), the maximum packing density can be obtained as high as 0.7522 which has overcome the maximum packing density of vibrated mono-sized sphere packing, and the method provides us with an effective way to realize much higher packing density.The successful completion of the project is very meaningful to study the materials structure and their transition in high packing density area in phase diagram and the realization to break through FCC or HCP densest packing for higher packing density.