| Rolling finishing technology,as a typical free abrasive surface finishing method,can not only improve the surface quality of parts,but also improve its physical and mechanical properties,and has been widely used in the final processing of various parts.At present,the overall research level of barrel finishing has been greatly improved,and the main research content is concentrated on theoretical analysis,model establishment,new process development,processing medium selection and process parameter optimization.However,there is still a lack of a quantitative description of the force chain of the granular medium in the barrel finishing process.The failure to accurately construct the flow field of the granular medium leads to the inability to effectively solve the problems of part processing efficiency and processing uniformity,which greatly limits the development of this technology.Based on the discrete element method,this paper numerically simulates the spindle-type barrel finishing and extracts relevant data,studies the force chain in the granular media,analyzes the spindle-type barrel finishing mechanism,and explains the granular media.The action mechanism of the workpiece provides a theoretical basis.The main research contents are as follows:(1)In order to study the force chain of the granular medium,the internal force chain of the granular medium needs to be extracted.Based on the simulation results of discrete element software,relevant data is extracted,and the power chain is extracted using the powerful data processing capabilities of the Python according to the three major conditions for the formation of the power chain.(2)For the spindle-type barrel finishing,a simplified model was established using discrete element software PFC(Particle Flow Code),and the influence of force chain parameters such as force chain direction,force chain load rate,force chain distribution rate and coordination number on the force chain was analyzed.It can be found that with the gradual increase of the load on the loading surface,the direction of the force chain is biased toward the driving surface,the distribution rate and bearing rate of the strong chain also increase,and the coordination number also increases;as the friction coefficient of the granular medium gradually increases.The direction of the force chain is biased towards the driving surface,the greater the load-bearing rate and distribution rate of the strong chain in the system,the more uniform the movement of the granular medium and the greater the coordination number.As the speed of the driving surface increases,the direction of the power chain is biased toward the driving surface.The load-bearing rate and distribution rate of the strong chain are not proportional to the speed of the drive surface.The coordination number is the largest.(3)Taking spindle-type barrel finishing as the research object,a two-dimensional simulation model was established to study the effect of drum speed and particle medium diameter on the force chain characteristics of the particle media group in the drum during the barrel finishing process.By establishing the number of force chains,The length,strength and quasi-straight line coefficient evaluation standards quantify the force chain.Analysis shows that under the same conditions,when the drum speed increases from 40 rpm to 120 rpm,the number of force chains increases by 37.5%,the strength of the force chain increases by 1.5e+6 N/m,the quasi-linear coefficient of the force chain increases by 5.5%,and the length of the force chain remains unchanged;The diameter of the granular medium is within 4mm-10 mm.As the diameter of the granular medium increases,the quasi-linear coefficient of the force chain increases.The more stable the force chain system is,but the relative motion between the granular media in the drum weakens.Conversely,the smaller the diameter of the particulate medium,the greater the number of force chains and the greater the strength of the force chain.(4)PFC-3D is used to simulate the change of the three-dimensional force chain during the spindle-type barrel finishing process,the characteristics of the force chain at different fixed angles of the workpiece are studied,and the strength of the force chain,the direction of the force chain,and the contact force with the workpiece.The five parameters of chain number,quasi-linear coefficient of force chain and total number of force chains are the main quantification standards for spindle-type barrel finishing and finishing force chains.By analyzing the material removal rate of the workpiece through the quantitative standard of the power chain,the analysis shows that: the processing angle is within 0 °-90 °,the strength of the power chain gradually increases,the direction of the power chain gradually decreases,and the number of power chains in contact with the workpiece gradually decreases.The number of total force chains gradually decreases,and the number of quasi-straight lines of force chains gradually increases.When the processing angle is within 90 °-157.5 °,the strength of the force chain gradually decreases,the direction of the force chain gradually increases,the number of force chains in contact with the workpiece gradually increases,the number of total force chains gradually increases,and the number of force straight lines gradually decreases.The research work verified the feasibility of the force chain for analyzing barrel finishing.The force chain extraction program laid the foundation for quantitatively studying the characteristics of the force chain.Dimensional and three-dimensional analysis provides a theoretical basis for explaining the mechanism of the granular medium on the workpiece from a meso level. |
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