基于FEM-DEM的三体摩擦界面中接触行为与应力的多尺度分析

The multi-scale analysis of contact behavior and stress in the three-bodies tribological interface based on FEM-DEM

为了研究三体摩擦界面中第一体变形与第三体状态的相互影响,利用耦合有限元法和离散元法的多尺度法模拟了平行板剪切颗粒第三体的过程。整个模型分为两个区域:有限元区域(上板)和离散元区域(第三体和下板),上板在一定的外载荷压应力下挤压颗粒第三体,下板以恒定的速度剪切颗粒第三体。为实现两个子区域间的相互联系,建立了子区域间应力应变的传递机制。实现了三体摩擦界面的多尺度分析,模拟了平行板剪切颗粒第三体的过程。模拟结果表明:当外载荷压应力低于10MPa时,颗粒间的碰撞增多使得第三体内量纲归一化平均应力增大,宏观摩擦系数也随之增大;在剪切过程中,第三体内部颗粒间的接触随接触角度的分布呈现出一定的规律性,0-90°各区间内的强接触较多,尤其在54°-72°之间;颗粒接触随接触力大小的分布也具有一定的规律性,接触力与第三体颗粒平均接触力的比值在0-0.6之间内的接触较多,随后接触力越大,接触数越少。同时,第一体内压应力分布与第三体内力链的分布相对应,力链越强则与其接触的第一体的压应力越大。

In order to account for the interaction of first body deformation and third body rheology in the three-bodies interface,multi-scale method based on coupling FEM and DEM is used to model the shear process of two parallel plates between which are full of solid particles.The model has two subregions: the FEM region(upper body) and the DEM region(third body and lower body).The upper body compresses the third body under a certain pressure and the lower body shears it at a constant velocity.A stress-strain transmission mechanism is established to achieve the interaction of two subregions.The results show that the mean dimensionless stress in the third body and the global friction coefficient increase because of strong collisions among particles under low pressures.During the shear processes,the particle contact distributions in the third body are regular: the strong contacts between particles appear more from 0 to 90°,especially from 54° to 72°.And there are more contacts possessing small contact force,about 0~0.6 times the mean contact force in the third body,and the larger the contact force is,the less the contact number is.Meanwhile the compressive stress profiles in the FEM regions correspond to the force chain distributions in the DEM regions.