Study On Macro-mesoscopic Mechanical Properties Of Single Particle Crushing

Particle breakage is widely found in nature,industrial production and human life,which is a research hotspot in the field of many currents.The research of particle breakage has great influence to the producing of materials and industrial production.Based on the discrete element method of aggregating particle crushing is a frequently-used numerical simulation method,many scholars research results show that both particle breakage of mesoscopic parameters selection and particle shape have significant effect on particle breakage.However local damping coefficient,the coefficient of friction between particles and particle material heterogeneity degree to the influence of particle breakage mechanism is still not perfected,particle shape on the particle breakage types and characteristics of fragment size distribution needs to be studied further.For detailed studying macroscopic micromechanics response of the single particle crushing,the physical experiment data of scholars at home and abroad were reviewed in this paper,statistical analyzing the influence factors of Weibull modulus,size effect and the type of single particle breakage;Discrete element agglomeration method was used to simulate single particle crushing and the material parameters affecting the particle breakage behavior were systematically analyzed to study the mechanism on the macroscopic mechanical behavior of particle crushing.Single particle crushing physics experiment were carried out,establishing a real particle model of physical test material particles with the aid of three-dimensional laser surface scanning technique,through the real particle shape aggregate of single particle numerical compression test to study the effect of particle shape on the particle breakage,meanwhile comparing with the physical test results to find the connection between the fragmentation distribution characteristic of the particle breakage type and the crushing strength.For the study of different particle material mesoscopic parameters on the particle breakage mechanism,choosing the sphere particles to carry out the friction coefficient between sub-particles,the minimum radius of sub-particles,bond strength and local damping coefficient.The simulation results show that the effect of bond strength on single particle crushing is most prominent,and the particle crushing strength increases linearly with the bond strength.Secondly,the smallest particle size changes the internal structure of the particle.Furthermore,With the increase of friction coefficient between sub-particles,the bond becomes more and more difficult under shear stress,which cause the particle crushing strength increases accordingly.The local damping coefficient has the least influence on it,but it can inhibit the stress wave formed by bond broken,thus changing the spatial distribution of the agglomerate's broken bonds.Therefore,it has a significant impact on the fragment size distribution of the agglomerate.In the study on the influence of granular material heterogeneity,it was found that the heterogeneity of the microscopic composition could be characterized by the radius ratio sub-particles.The study found that the more heterogeneous the microscopic composition was,the larger the radius ratio was,the greater the dispersion of the particle crushing strength and the smaller the average coordination number,so the particle characteristic crushing strength decreasing.The heterogeneity of the granular materials strength spatial distribution can be simulated by Gaussian distribution,it has a significant effect on the particle breaking strength and the crushing mechanism,but not effect on the Weibull modulus.The variability of the internal structure is the main factor affecting the granular materials Weibull modulus.In the process of particle breakage,the number of shear failure cracks increased with the increasing of the material heterogeneity and the particle breakage mechanism changed.To explore particles breakage type and fragments distribution characteristics,choosing similar shape and particle size of white onyx particles,introduction the three dimension scanning technology to rebuild the real physical particle shape,carrying out the physical single particle compression and measuring the debris quality after each sample particle breaking,through the real particle shape of single particle crushing numerical experiments to analyzing the influence of particle shape on the particle breakage process,studying different particle breakage types of fragmentation distribution characteristics and the mechanism of particle breakage,exploring the connection between peak particle crushing strength and the particle breakage types.Due to the particle shape has edge stress concentration thus caused the force displacement appear more peak curve,white onyx particle breaking type is given priority to with middle fracturing,breakage types by different fragments particle size can be character by the first three debris of the particle.In different types of particle breakage,random cracking failure mode has the largest breaking strength,the breaking strength of middle crack mode is larger than the contact mode's.