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在金属粉末高速冲击压制中,颗粒间的高速碰撞是一个重要因素,研究其相互间的碰撞接触力传递过程是个难点。研究采用基于离散单元法(DEM)的PFC2D颗粒流程序,从微观层面着手,建立三颗粒碰撞模型,探讨碰撞过程中摩擦因素、碰撞速度、剪切模量对接触力传递的影响规律。研究发现,颗粒在碰撞过程中会发生转动,在碰撞的起始及收尾阶段,颗粒处于滑动摩擦状态,而中间阶段则因处于静摩擦状态,颗粒发生了转动。数值模拟结果表明:模壁摩擦系数几乎不影响颗粒的接触力及碰撞时间,而颗粒间的摩擦系数会同时影响法向及切向接触力的大小;碰撞速度越大,颗粒间法向重叠量就越大,相应的接触力峰值也越大;剪切模量的不同也会影响到颗粒间接触力的传递情况。这些结果可对金属粉末高速压制致密化机理的微观研究提供一定的指导作用。
In the high-speed impact press of metal powder, the high-speed collision between particles is an important factor, and it is difficult to study the contact force transmission process between them. The PFC2D particle flow program based on discrete element method (DEM) was used to study the influence of friction factors, collision velocity and shear modulus on the contact force transmission in the collision process. It is found that the particles rotate during the collision, and the particles are in the state of sliding friction at the beginning and the end of the collision, while the particles rotate due to the static friction in the middle stage. The numerical simulation results show that the friction coefficient of the mold wall has little influence on the contact force and the collision time of the particles, but the friction coefficient between the particles will affect the normal and tangential contact forces at the same time. The larger the collision speed, The larger the corresponding peak contact force; the different shear modulus will also affect the transmission of particles between the contact force. These results can provide some guidance for the microscopic study of the mechanism of high-speed compacting and densification of metal powders.