Abstract
This work deals with the effect of the contact orientation distribution on the crushing of granular materials. At first, a simple drop weight experiment was designed in order to study the effect of the location of three contact edges on the fracture pattern and the strength of a model cylindrical particle. The sample was placed on two bottom contact edges symmetrically distributed with reference to the vertical symmetry plane of the particle and subjected to an impact at the top. Angle α between the plane connecting a bottom contact edge to the centerline of the cylinder and a vertical plane was varied. The energy required to fracture the particle was shown to be an increasing function of angle α. Peculiar crack patterns were also observed. Then, we present a discrete model of grain fracture [1] and employ it for a numerical analysis of the problem. The cylindrical particle is discretized by means of a space filling Voronoi tessellation, and submitted to a compression test for different values of angle α. In agreement with experiments, simulations predict a strong effect of the contact orientation on the strength of the particle as well as similar fracture patterns. The proposed numerical model is therefore an interesting tool for understanding fracture mechanisms with the purpose of optimizing the crushing process.
Highlights
Studying the fragmentation of cohesive materials is of importance for a wide range of natural and industrial processes
For different values of the angle α, the probability of breaking the sample is displayed in Figure 1b as a function of the input energy. 20 to 30 tests were performed for each energy value
The effect of the contact orientation distribution on the crushing of granular materials was studied by means of experimental and numerical tools
Summary
Studying the fragmentation of cohesive materials is of importance for a wide range of natural and industrial processes. In the production of aggregates, rock blocks are crushed and the resulting fragments are required to meet high standards namely in terms of size and shape. Successive crushing steps are usually carried out to achieve the requested aggregate characteristics, leading to a waste of good quality raw materials and a high energy cost that could both be mitigated upon improving the crushing efficiency. An important aspect of the crushing process is that loads are applied on a collection of particles, and stresses are transmitted through particle contacts. In this perspective, some authors have proposed failure criteria for tensile [2] and plane shear [3] fracture modes taking into account the effect of the coordination number. The effect of anisotropy of the contact points location on the strength of the particle has not been deeply investigated
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