Cutting processes of agricultural stalk goods: Maize - experiment and simulation

切碎滚筒的切割过程是玉米收获的主要工作过程，占总功耗的50%以上。许多工艺参数和随后的切碎材料的加速影响切割过程的功耗。为了优化这一过程，减少功耗，一个计算机辅助程序的基础上相结合的离散单元法（DEM）和虚拟单元法（VEM）是在本研究项目开发，与切削过程可以模拟。在广泛的实验活动的帮助下，将在玉米秸秆上校准和验证建模方法。在秸秆收获领域，DEM用于绘制和优化收获过程中机器内的作物流。当用离散元研究分离行为时，柄由颗粒组成，颗粒之间形成唯象的结合律。DEM的主要缺点是DEM的接触力学不考虑物理输入变量，例如刀片几何形状（切割和攻角）或切割过程中的切割速度。因此，切割过程的债券映射，除其他事项外，通过实验确定的特性图来描述材料的故障。在本研究项目中，特征图是由一个高分辨率的VEM模型的帮助下，而不是一个精心设计的实验活动的分离过程的本地分析确定的。层特定的材料特性，材料故障和切削工艺参数的信息被纳入VEM模型。VEM模型的一个显著优点是可以在模拟中设置不同的工艺参数，从而获得材料失效、反作用力、功耗和工艺参数之间的相关性。为了能够使用VEM模型来校准玉米秸秆DEM模型中的约束参数，通过在秸秆组织水平和整个秸秆上的实验来确定秸秆的结构力学、材料和破坏特性。

The cutting process at the chopping drum represents the main working process of a forage harvester for maize harvesting, accounting for more than 50% of the total power consumption. Numerous process parameters and the subsequent acceleration of the chopped material influence the power consumption of the cutting process. In order to optimize this process with regard to a reduction of the power consumption, a computer-aided procedure based on the combination of the Discrete Element Method (DEM) and the Virtual Element Method (VEM) is to be developed in the present research project, with which the cutting process can be simulated. With the help of an extensive experimental campaign, the modelling approach will be calibrated and validated on maize stalks. In the area of stalk harvesting, the DEM is used to map and optimize the crop flow within the machine during the harvesting process. When investigating the separation behavior with DEM, the stalk is built up of particles between which a phenomenological binding law is formulated. A major disadvantage of the DEM is that the contact mechanics of the DEM do not take into account physical input variables such as the shape of the blade geometry (cutting and angle of attack) or the cutting speed during the cutting process. Therefore, the cutting process of the bonds is mapped, among other things, by an experimentally determined characteristic diagram to describe the material failure. In the present research project, the characteristic map is to be determined by a local analysis of the separation process with the help of a high-resolution VEM model instead of an elaborate experimental campaign. Layer-specific material properties, information on material failure and cutting process parameters are incorporated into the VEM model. A significant advantage of the VEM model is the possibility to set different process parameters in the simulation and thus obtain a correlation between material failure, reaction force, power consumption and the process parameters. In order to be able to use the VEM model to calibrate the binding parameters in the DEM model of the maize stalk, the structural mechanical, material and failure properties of the stalk are determined by experiments at stalk tissue level and on the entire stalk.