研磨抛光颗粒流剪切膨胀及力链演变的力学机制

Mechanical Mechanisms of Shear Dilatancy and Force Chain Evolution in Abrasive Polishing Granular Flow

将研磨抛光作为后处理可以提高工件的表面质量,如何将研磨抛光工艺价值最大化是本文首要解决的问题。由于颗粒流润滑既适用于极端环境又具有环保作用,因此本文将颗粒流用于研磨抛光。通过离散单元法建立平行板结构模型,将颗粒流作为第三体填充至摩擦副间隙,将工件表面与刀具作为第一体对颗粒流体系施加法向力和剪切力,对研磨抛光过程进行数值模拟。研究结果表明:单个颗粒剪切膨胀过程可以分为上升阶段、最高点阶段和下降阶段,不同阶段的弱力链方向都偏向于x轴,其中上升阶段强弱力链方向稳定,可提高工件的加工效率以及表面质量。当载荷的较大,会使强弱力链的分布律与承载率稳定,当载荷较大及较小时,剪切膨胀率降低,强力链方向更偏向于x轴。通过本研究,可以将不易检测的力链和剪切膨胀现象进行数值模拟,为研磨抛光条件下使用颗粒流提供了理论基础。

The use of grinding and polishing as post processing can improve the surface quality of a workpiece.This paper mainly solves the problem of how to maximize the values of grinding and polishing processes.Since granular flow lubrication is suitable for extreme environment and environmental protection,the paper uses granular flow for grinding and polishing.A parallel plate model was established with the discrete element method.Granular flow was used as the third body to fill the gap between friction pairs,and the workpiece surface and tool were used as the first body to apply normal force and shear force to the granular flow system.The polishing process was numerically simulated.The results show that the shear dilatancy process of a single particle can be divided into rising stage,peak stage and falling stage.The weak chain direction in different stages is inclined to the x axis.In the rising stage,the weak chain direction is stable and can improve the machining efficiency and surface quality of the workpiece.When the load is large,the distribution law and the bearing rate of strong and weak force chains are stable.When the load is small,the shear dilatancy rate decreases and the strong chain direction is inclined to the x axis.This study numerically simulates the force chain and shear dilatancy that are not easily detected,thus providing a theoretical basis for the use of granular flow under the condition of grinding and polishing.