| With the wide application of the granular material fracture in the field of basic industry,the research on particle breakage process is helpful to understand the granular broken essence.The construction of particle model suitable for the description of granular crushing process has become a hot issue in the field of crushing by using computer technology.Combining with the experimental analysis,theoretical analysis and computer simulation,the accomplished work of the present can be summarized as follows.On the foundation of the discrete element model(DEM)of hard brittle rock particle,microscopic parameters of particles are analyzed and calibrated.Based on the general particle breakage model,the concept of multi-scale cohesive(MSC)particle modelis proposed to describe the crushing process of particle vibration and the multi-scale structure and the definition of the multi scale of cohesion are completed.Finally,according to the MSC particle model the analysis of single particle vibration extrusion process is carried out and the visualization of particle group breakage is studied.The main work of this thesis show as flows.(1)On the basis of uniaxial compression test,the DEM of ore particle is constructed and the discrete element model of ore particle is constructed,and the discrete element nature of the DEM parameters is discussed.Meanwhile with "virtual experiment" method and comparison of the stress strain curves and sample's fracture surface location of the simulation and experiment,the microscopic parameters of the particle model are calibrated.Then a set of micro bond parameters of the particles to simulate the fracture behavior of brittle ore are obtained.(2)Based on the description of the fracture process of ore particles under extrusion,a MSC particle model is established with the definition of the different geometrical characteristics of the unit and the combination method and different bond strength of the element.In EDEM,the MSC granular cylinder model is generated,which has the same physical characteristics with the standard cylinder.Then the rationality of the model is verified by compression simulation.(3)Through the establishment of plate roller vibration extrusion crusher model,the simulation of single particle vibration extrusion and fragmentation is carried out on the MSC particles model.Analysis results show that: in the extrusion process,three-level particles and secondary particles appear initial cracks initiation and cracks extend,which accord with the characteristics of MSC model.The impact of bite velocity on particle model is only reflected in the time of action.The faster broken particle model occurs with the greater bite velocity.But the fracture state and form are not affected by the biting velocity variation.The fragmentation process of the particle model under vibration loading is still in accordance with the MSC characteristics.The crack growth rate of the model under vibration is faster than that of pure extrusion,and the crushing effect is better than that of pure extrusion.(4)Particles group crushing model based on MSC model are established,which contain 18 typical multi scale granular structures that belong three kinds of different shapes.The particle vibration extrusion crushing process visualization is realized.Compare two states of the pure squeeze and vibration extrusion,the comparative analysis of influence on particle group crushing effect is given.The result shows that: The application of vibration is beneficial to the fragmentation of the particle swarm.Meanwhile,crushing rate of the particle group of MSC particle model is first slowly increase and then rapidly increases with the compression distance increase.This fracture characteristic of the particle swarm crushing process is further verified from the point of view of force chain.Through the above shows,the research of this paper can be used to build a new type crusher,which provides an effective way to build a new type crusher and has well practical application value. |
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