沙柳颗粒致密成型过程中的颗粒运动及能量分析

Analysis on particle movement and energy in dense molding process of salix particles

为了研究沙柳致密成型过程中颗粒运动及能量变化的规律,运用离散元颗粒流软件PFC3D建立了长径比为5∶1的颗粒模型。按照应力-应变曲线的特点,将沙柳致密成型过程划分为3个阶段:松散阶段、压密阶段和塑性阶段,从3个阶段中各选取一个时间点,对颗粒速度变化、位移变化、受力分量的变化以及能量变化进行细致分析。结果表明:颗粒速度及位移变化的主要影响因素为压力,在压力传递过程中,颗粒间接触力和墙体的反作用力不断变化,沿X轴、Y轴方向的速度分量和位移分量渐渐增多;从松散阶段到压密阶段,颗粒位置重新排列,间隙不断改变,动能呈现波动性变化;在塑性阶段时,压力克服颗粒间作用力的最大值,颗粒变形产生塑性流动,间隙不断减小,动能逐渐增大。在整个压缩过程中,粘结能增长趋势放缓,其他耗散能所占的比重逐渐增加,为了减少能量的损耗,应把应变值控制在较小的范围内。

In order to study the laws of particle movement and energy change in the dense molding process of salix,a particle model with aspect ratio of 5∶1 was established by discrete element particle flow software PFC3 D.Then,according to the characteristics of stress-strain curve,the dense molding process of salix particles was divided into three stages,such as loose stage,compaction stage and plastic stage.Furthermore,from each of the three stages,a time point was selected to detailed analyze the changes of particle velocity,displacement,force component and energy.The results show that the main influencing factor of particle velocity and displacement changes is pressure.During the process of pressure transmission,the contact force between particles and the reaction force of wall change continuously,and the velocity component and displacement component along the X-axis and Y-axis direction gradually increase.From the loose stage to the compaction stage,the particle position is rearranged and the gap changes continuously,and the kinetic energy shows fluctuating changes.In the plastic stage,the pressure overcomes the maximum force between particles,the particle deformation produces plastic flow,the gap decreases continuously,and the kinetic energy increases gradually.In the whole compression process,the growth trend of bond energy slows down,and the proportion of other dissipated energy gradually increases.Thus,in order to reduce the loss of energy,the strain value should be controlled within a small range.