Mesoscopic Scale Behavior Analysis Of Granular Media In Horizontal Vibration Mass Finishing

The mass finishing technology is a widely used surface finishing technology.The complex relative motion between the workpiece and the media produces a micro-grinding effect on the workpiece surface during processing,and comprehensively improves the surface integrity of the workpiece surface.The research on mass finishing technology has made great progress in theoretical analysis,new technology development,advanced testing technology,etc.But the dynamic behavior of media and the action mechanism of media on workpiece surface are very complicated,and at present,there is still a lack of research on quantitative description and precise control strategy of particle flow field.At the same time,there is little research on revealing the behavior of media from micro,meso and macro multi-scale.In this paper,the discrete element method is used to study the horizontal vibration mass finishing.The macroscopic motion behavior of media during processing is analyzed.The relationship between the evolution mechanism of the force chain network of the particle system and the macroscopic motion behavior of the particles is explored.Cloud map of wear depth on workpiece surface is explained based on the force chain network characteristics of different regions.The main research contents are as follows :(1)The quantitative description criterion of force chain and the specific retrieval algorithm are determined,the force chain retrieval program is developed and the feasibility of the method is verified by photoelastic test.(2)Based on the discrete element software EDEM,horizontal vibration mass finishing model is established.The macroscopic kinematic behavior of media with different amplitudes(frequencies)is analyzed,the particle flow field is quantitatively described by the overall velocity,horizontal velocity and velocity ratio,and the change of macroscopic motion behavior of media after adding workpiece is compared and analyzed.(3)Based on the discrete element software PFC2 D,a two-dimensional discrete element model is established.The relationship between the space-time distribution evolution of the mesoscopic scale force chain network and the macroscopic behavior of the particles is analyzed,and the characteristics of the force chain network of the particles under different states are determined.Five quantitative indexes,including the number,alignment coefficient,strength,length and directional coefficient of force chains are used to characterize the internal force chain network of the particles under excitation load,and analyze the relationship between the change of overall characteristics of force chain network and the change of macroscopic behavior under different amplitudes(frequencies).(4)The influence of different amplitudes(frequencies)on the force chain network character and macroscopic behaviors of particles in different regions is explored.On this basis,the surface wear depth cloud map of workpiece is explained,and the difference of the influence of amplitude and frequency on the dynamic behavior of fluidized particles is found from mesoscopic perspective.