软固结磨粒群微观力学特性分析与试验研究

Analysis of Micromechanical Characteristics of Softness Consolidation Abrasives

针对软固结磨粒气压砂轮加工过程中磨粒群内部发生剪胀效应,造成磨粒群表面局部堆积,进而引起工件表面产生划痕、降低二次精加工效率和表面质量的问题,建立磨粒群内部微观接触力学模型,揭示磨粒群内部力链传递过程。采用Li-Dafalias弹塑性剪胀本构模型,来反映磨粒群内部微观力-位移的关系。通过颗粒流三维分析PFC3D软件数值模拟具有不同孔隙率的磨粒群力链网络演化过程,以及加工件表面压强分布,结果表明:当孔隙率超过44%后,磨粒群内部力链传递路径消失;工件表面压强呈周期分布,随着孔隙率增大,压强幅值减小。搭建试验平台,通过光整加工试验得到孔隙率和磨粒目数对工件表面粗糙度的影响规律,结果显示:当采用磨粒目数800、孔隙率24%时加工得到的工件表面粗糙度较小,表面粗糙度轮郭算术平均偏差从313.74nm降低到67.11nm.

A model of microscopic contact mechanics inside abrasives group is established to analyze the force chain transfer process. The Li-Dafalias elastoplastic dilatant constitutive model is used to reflect the relationship between micro-force and displacement within the abrasives group. The evolution of force chain network of abrasives group with different porosities and the pressure distribution on workpiece surface were simulated using the three-dimensional particle flow code (PFC3D) software. The simulated results show that, when the porosity exceeds 44%, the internal force chain transmission path of abrasives group disappears;the surface pressure of workpiece exhibits a periodic distribution, and the pressure amplitude decreases with the increase in porosity. A test platform was set up, and the influence laws of porosity and abrasive mesh on the surface roughness of workpiece can be concluded after a series of polishing experiments by pneumatic grinding wheels with softness consolidation abrasives. The experimental results show that the contour arithmetic mean deviation of workpiece surface roughness is small and decreases from 313.744 nm to 67.11 nm when the abrasive mesh is 800 and the porosity is 24%.