Experimental Study On The Densification Of Mono-sized Sphere Packing Subjected To 1D And 3D Vibrations

In this thesis, systematically physical experiments were carried out to study the densification of mono-sized sphere packing subjected to one-dimensional (1D) and three-dimensional (3D) vibrations. By adopting two different particle feeding methods in 1D and 3D vibrations, i.e. total feeding and batch-wise feeding, we systematically studied the influence of vibration parameters such as vibration time t, amplitude A, frequency co and vibration intensityΓ(Defined as F=Aω2/g, where g is gravity acceleration), batch of each feeding B, and container wall (container size) on particle packing density.For packing under 1D continuous vibrations, densification can be realized by properly choosing vibration amplitude A, frequencyω, and feeding mode. (1) In the case of total feeding, the transition of particle packing from random loose packing (RLP) to random close packing (RCP) can be reproduced. Through the extrapolation on packing density using different sized containers to eliminate the wall effect, we observed that the maximum packing density can reach 0.6360 under the 1D vibrational condition of A=0.1d andω=210Rad/s, which satisfactorily proves our numerical results. (2) In the case of batch-wise feeding, through the extrapolation on packing density, we found that the maximum packing density can reach 0.6632 when A=0.1d andω=200Rad/s, which is much higher than RCP limit 0.64. And it also showed that batch B has a strong effect on packing density.For packing under 3D continuous vibrations, much denser packing than the maximum packing density of RCP can be overcome in either total feeding or batch-wise feeding. (1) In the case of total feeding, it is found that partial ordering (crystallization) will be realized in packing under appropriate vibration conditions. Through extrapolation we obtained the maximum packing density of 0.6890 when A=0.1d and co=70Rad/s. (2) In the case of batch-wise feeding, the experimental results indicated that ordered packing can be formed by properly controlling the vibration conditions. With A=0.1d,ω=70Rad/s, and B=1 layer/batch, the extrapolated packing density can reach 0.7399 which corresponding to the packing density of Face Centered Cubic (FCC) or Hexagonal Closed Packed (HCP) crystals. Through the analysis on the obtained order structure, we found that it belongs to FCC crystal, which is in good agreement with our numerical results and also indirectly proves that the FCC structure is more stable than HCP structure.No matter in ID vibrated packing or in 3D vibrated packing, there exist optimum values forωand A to achieve the maximum packing density. The effects of A andωcannot be simply represented by a single parameter, such as vibration intensityΓ, instead, they should be considered separately. Therefore, choosing the proper A and co is the precondition for higher packing density.In our experiments, we can control the amplitude A and frequency co precisely by eccentric wheels and frequency inverter. In this case, we can realize the study of particle packing under vibration conditions quantitatively.