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方法模拟(DEM)，例如药物粉末，以更好地预测微观和宏观机械性能。到目前为止，高塑性颗粒变形和低孔隙率是一个挑战，这使得DEM无法作为压片工艺和配方设计的标准工具。已经建立了DEM的多接触接触模型，并由申请人成功地测试了以弹性变形和中等压实程度为主的DEM。然而，为了能够模拟工业上相关的过程，如粉末压制和压片，必须额外记录材料的塑性变形和高压缩应力下接触表面的变化，并在现有模型中实现。其目的是建立基于机械依赖的多接触接触模型，并用实验数据对其进行校准和验证。随后，将从结构参数方面对实验进行分析。然后结合有限元和离散元模拟方法，系统地研究了微细结构参数的变化及其对接触力的影响。此外，还将通过自动局部模型评估、模型开发和使用遗传算法的参数化来识别更复杂的物理依赖关系并将其整合到新的接触模型中。多接触模型的验证和最终适应将通过模拟和实验研究的方式进行，该模型系统在装备齐全的“压实模拟器”中使用。

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".