R. P. Zou

Coordination number of binary mixtures of spheres

This paper presents an experimental study of the coordination number of binary packings by the use of the liquid bridge technique and provides detailed information about the distributed coordination numbers corresponding to different types of contacts between small and large components and their dependence on particle size distribution. The results indicate that increasing the volume fraction of small component increases the small-to-small and large-to-small contacts and decreases the small-to-large and large-to-large contacts; and this trend is more apparent for a packing with a large size difference. For the packings under gravity, the overall mean coordination number is essentially a constant and independent of particle size distribution.

Stress distribution in a sandpile formed on a deflected base

This paper presents a study of the pressure distribution beneath a sandpile by means of discrete element method. Simulations were performed with spheres of different properties for wedge-shaped sandpiles formed on bases of different degrees of deflection. The results are analyzed in terms of the stress distribution, and normal and shear pressure distributions beneath a sandpile. It is shown that the interparticle forces in a sandpile are highly disordered and mainly propagate with large force chains. Base deflection has a significant effect on the normal pressure distribution when a sandpile is formed with multisized particles and small sliding friction coefficients. However, it is not the sole factor leading to a normal pressure distribution with a dip, particularly when a sandpile is formed with monosized particles.

Formation characteristics of nano-clusters during rapid solidification process of liquid metal Al

Recently, a lot of work, both experimental and theoretical, is focused on nano-clusters formed by evaporation, ionic spray methods and so on [1–6], however, the other kind of nano-clusters, formed in liquid metallic systems during solidification processes, is still neglected up to now. It is well known that for investigating the formation characteristics of nanoclusters during solidification processes of liquid metals, it is necessary to trace the transition processes of microstructural configurations in the system step by step. Under present experimental conditions, it is difficult to complete such a tracking research. Fortunately, due to the rapid development of computer technique, the molecular dynamics method has been used to make such a tracking study, and some very clear physical pictures of the instantaneous processes of microstructure in a small liquid metal system consisting of 500 Al atoms have been obtained in the past years [7–12]. However, in the small system, it is still difficult to research the clusters, especially the nano-clusters. In this paper, based on the author’s works [10–12], a large-scale liquid system consisting of 400 000 Al atoms has been used to perform a simulation study on the formation process of nano-clusters during rapid solidification by using constant-pressure molecular dynamics method and parallel algorithm on the Clare supercomputer. The conditions for simulation calculation are as follows: at first, the 400 000 Al atoms are placed in a cubic box and their calculation task is distributed into 40 machines, and then the system runs under periodic boundary condition. The interatomic potential adopted here is the effective pair potential function of the generalized energy independent non-local model–pseudopotential theory developed by Wang et al. [13, 14], and the function is