球磨机DEM仿真中接触模型的精准性分析

Analysis for the Mechanical Characteristics of Contact Models in the DEM Simulation of a Ball Mill

颗粒-边界间的接触力通常由接触模型来求解,它是DEM仿真中的核心技术问题之一。以球磨机颗粒系统力学特性的数值模拟为背景,首先归纳了三种常用的接触模型LS、HM和H-DD。然后,将三者用于单颗粒-衬板间碰撞过程的DEM仿真,分析了三者恢复系数和法向力-位移曲线的变化。结果表明:在无滑移时H-DD预测的切向恢复系数更加真实,在滑移时三者均能有效预测切向恢复系数;HM和H-DD预测的法向力-位移曲线更合理。最后,将三者用于球磨机多颗粒研磨过程的DEM仿真,比较了三者功率预测的准确性,结果表明:中低转速下HM预测的功率更精准,高转速下H-DD预测的功率更接近真实实验数据。上述分析为不同工况下球磨机DEM仿真中接触模型的合理选用以及颗粒-边界间接触力的精准求解提供了依据和参考。

The contact force between the particle and structural boundary is generally calculated by the contact model, which is one of the core technical issues in the DEM simulation. On background of the numerical simulation for the mechanical characteristic of the granular system inside a ball mill, this paper generalizes the three common-used contact models firstly, including LS, HM and H-DD. Then, through simulating the collision process of a single particle onto a mill liner, the variations of the restitution coefficient and force-displacement curve among the three models are analyzed, respectively. The results showed that the tangential restitution coefficient by H-DD is more close to the experimental data, when the slip not occurs;while the tangential restitution coefficients by the three models consist with the experimental data, when the slip occurs. The normal force-displacement evolutions by HM and H-DD are more reasonable than by LS during the collision. Finally,through modeling the grinding process of multiple particles inside a ball mill, the power draw predicted by the three models are compared. The results showed that the power draw by HM is more consistent with the experimental data at the low-medium mill speed;while the power draw by H-DD is more close to the experimental data at the high mill speed. The above comparisons provided a basis and reference for the reasonable usage of the contact models in the DEM simulation of a ball mill and for the accurate calculation of the contact force between the particle and boundary.