Abradable DEM: A novel framework to capture the mechanistic evolution of particle shape

Although various methods exist for modelling non-spherical particles in DEM, particles’ shapes are usually treated as immutable. However, particles often change shape gradually, e.g., due to abrasion or accrued plastic deformation. This manner of shape evolution has largely been neglected in DEM, even though it can significantly influence bulk-scale behaviour. The following introduces an extendable framework for modelling the gradual and permanent evolution of particle shapes in DEM, focusing on abrasion. By extending the LAMMPS rigid-body implementation, a comprehensive novel wear model is adapted to simulate the abrasion of arbitrarily shaped particles. Abradable particles are represented as hollow shells of discrete spheres which compute forces via standard pair interactions. These spheres form the nodes of a triangulated mesh used to calculate well-defined local surface areas and normals. Following an impact exceeding a material yield criterion, spheres are displaced inwards along their associated normals. The result is a reduction in volume and a permanent change in shape. Each abraded particle’s moment of inertia is then recomputed to resolve future rigid-body dynamics. Thus, particle-level changes in shape affect the system’s bulk dynamics, which in turn informs subsequent abrasion. Results exhibit shape evolution in agreement with a variety of abrasion scenarios in literature and showcase the consequent effect on their bulk dynamics. By linking microscale abrasion mechanisms to macroscale system behaviour, the present research has widespread applications in both natural processes and industrial particle-handling systems. Furthermore, the outlined framework can be readily adapted to other sources of mechanistic particle shape evolution in DEM.尽管目前已有诸多方法可用于离散元法（Discrete Element Method，DEM）中非球形颗粒的建模，但颗粒形状通常被视为恒定不变的。然而实际工况中，颗粒形状往往会随时间逐渐改变，例如因磨损或累积塑性变形所致。尽管这类形状演化过程会显著影响系统的宏观行为，但在DEM研究中该现象长期以来被大幅忽略。下文将介绍一种可扩展的DEM颗粒形状渐次永久演化建模框架，重点聚焦于磨损过程。通过扩展LAMMPS的刚体实现模块，本研究适配了一套完整的新型磨损模型，以模拟任意形状颗粒的磨损过程。可磨损颗粒被表示为离散球体构成的空心壳层，这些球体通过标准成对相互作用计算受力。这些球体构成三角网格的节点，用于计算明确的局域表面积与法向量。当颗粒受到的冲击超过材料屈服准则阈值时，球体将沿其关联的法向量向内位移，最终导致颗粒体积减小且形状发生永久改变。随后，系统会重新计算每个磨损后颗粒的转动惯量，以求解后续的刚体动力学过程。因此，颗粒尺度的形状变化会影响系统的宏观动力学行为，而宏观动力学状态又会反过来为后续的磨损过程提供反馈。研究结果显示，颗粒形状演化过程与文献中多种磨损场景的表现一致，并验证了其对系统宏观动力学行为的后续影响。本研究通过将微观磨损机制与宏观系统行为相联结，在自然过程与工业颗粒处理系统中均具备广泛的应用前景。此外，本文所提出的框架还可便捷地适配DEM中其他由力学机制引发的颗粒形状演化场景。