Modelling collisions of soft agglomerates at the continuum length scale
Modelling collisions of soft agglomerates at the continuum length scale
复制标题
在连续长度尺度上模拟软团聚体的碰撞
DOI：
10.1016/j.powtec.2004.01.013
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发表时间：
2004
影响因子：
5.2
通讯作者：
J. Rance
中科院分区：
文献类型：
--
作者：
M. Adams;C. Lawrence;M. Urso;J. Rance
造粒过程中的生长和破碎机制可能涉及软塑性变形附聚物之间的碰撞。先前已经确定，在这种碰撞中的流动应力随着应变速率而增加，这取决于冲击速度和团聚体的尺寸。在目前的文件中，描述了一个缩放模型，是基于连续本构关系和制定的可访问的实验参数。它是一个现有的接触力学模型的弹塑性非粘性碰撞的扩展，因此限于变形中的接触半径小于约40%的团聚体半径。此外，假设弹性应变与最大值相比较小。有限元模拟进行了一系列的冲击速度和材料参数相关的弹粘塑性本构关系中使用的缩放模型的类型。结果被用来验证缩放模型。在规定的适用范围内，发现恢复系数、接触面积、加载和卸载曲线以及压缩位移的时间演变可以以相对较高的精度计算。此外，有人发现，对于粘塑性材料的恢复系数随冲击速度的增加而降低的速率大于塑性变形。该模型应被证明是有用的，在了解造粒系统中的碰撞过程，特别是那些发生在相对较高的冲击速度时，主要的能量耗散过程中产生的粘塑性变形。在这种情况下，粘附的影响可以忽略不计，并且当恢复系数小时，可以认为发生了聚结。
Growth and breakdown mechanisms in granulation processes may involve collisions between soft plastically deforming agglomerates. It has been established previously that the flow stress in such collisions increases with the strain rate, which is dependent on the impact velocity and the size of the agglomerates. In the current paper, a scaling model is described that is based on a continuum constitutive relationship and formulated in terms of accessible experimental parameters. It is an extension of an existing contact mechanics model for elastoplastic nonadhesive collisions and therefore limited to deformations in which the contact radius is less than about 40% of the agglomerate radius. In addition, it is assumed that the elastic strains are small compared to the maximum value. Finite element simulations were carried out for a range of impact velocities and material parameters associated with an elastoviscoplastic constitutive relationship of the type used in the scaling model. The results were employed to validate the scaling model. Within the specified limits of applicability, it was found that the coefficient of restitution, contact area, loading and unloading curves and also the time evolution of the compressive displacement could be calculated with relatively high accuracy. Moreover, it was found that for a viscoplastic material the rate of decrease of the coefficient of restitution with increasing impact velocity is greater than for plastic deformation. The model should prove useful in understanding collision processes in granulation systems, particularly those occurring at relatively high impact velocities when the main energy dissipation process arises from viscoplastic deformation. Under this circumstance, the influence of adhesion is negligible and coalescence may be taken to occur when the coefficient of restitution is small.