Multi-contact elastoplastic contact model for DEM-simulations of high load compaction derived from realistic microstructure

本项目的目的是进一步开发和验证一种新的弹塑性多接触模型，用于压实和压片的离散元法模拟（DEM），例如药物粉末，以更好地预测微观和宏观力学性能。迄今为止，高塑性颗粒变形以及低孔隙率是挑战，这阻止了DEM分别用作压片和压实中的工艺和配方设计的标准工具。申请人已经建立了DEM的多触点接触模型，并成功地测试了主要的弹性变形和中等压实度。然而，为了能够对粉末压制和压片等工业相关过程进行建模，必须在现有模型中额外记录和实现材料的塑性变形和高压缩应力下接触表面的变化。其目的是在机械相关性的基础上对多接触接触模型进行建模，并使用实验数据对其进行校准和验证。为了实现这一点，在初始阶段，将在微型计算机断层扫描仪（µCT）中压缩少量颗粒。随后，实验将分析相对于结构参数。结合有限元法和离散元法的模拟方法，系统地研究了微结构参数的变化及其对接触力的影响。此外，还将通过自动部分模型评估、模型开发和使用遗传算法的参数化，确定更多复杂的物理依赖关系，并将其纳入新的接触模型。多接触模型的验证和最终调整将通过对设备齐全的“压实模拟器”中使用的模型系统的压实进行模拟和实验研究来进行。

The aim of the present project is the further development and validation of a new elastic-plastic multi-contact model for the Discrete Element Method Simulation (DEM) of compaction and tabletting, e.g. of pharmaceutical powders, for better prediction of micro- and macromechanical properties. The high plastic particle deformations as well as the low porosities are challenges so far, which prevent the DEM from being used as a standard tool for process and formulation design in tabletting, respectively compacting. A multi-contact contact model for the DEM has already been established and successfully tested by the applicant for predominantly elastic deformation and medium degrees of compaction. However, in order to be able to model industrially relevant processes such as powder compaction and tabletting, the plastic deformation of the material and the change in the contact surfaces under high compressive stress must be additionally recorded and implemented in the existing model. The aim is to model the multi-contact contact model on the basis of mechanistic dependencies and to calibrate and validate it with experimental data.To realize this, a small number of particles will be compressed in a microcomputer tomograph (µCT) in the initial phase. Subsequently, the experiments will be analyzed with respect to structural parameters. In combination with the simulation methods Finite-Element-Method (FEM) and Discrete-Element-Method (DEM), the change of microstructural parameters and their influence on contact forces will then be systematically investigated. In addition, further complex physical dependencies are to be identified and integrated into the new contact model by means of automatic partial model evaluation, model development and parameterization using a genetic algorithm. The validation and final adaptation of the multi-contact model will then be carried out by means of simulation and experimental investigation of the compaction of the model systems used in a fully equipped "Compaction Simulator".