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

斩鼓处的切割过程是玉米收获饲草收获机的主要工作过程，占总功耗的50%以上。众多的工艺参数和随后被切割材料的加速影响切割过程的功耗。为了优化这一过程，降低能耗，本研究开发了一种基于离散元法（DEM）和虚拟元法（VEM）相结合的计算机辅助程序，可以对切削过程进行模拟。在广泛的实验活动的帮助下，建模方法将在玉米秸秆上进行校准和验证。在秸秆收获区域，利用DEM绘制和优化收获过程中机器内的作物流。当用DEM研究分离行为时，秸秆是由粒子组成的，它们之间形成了一种现象学的结合规律。DEM的一个主要缺点是，DEM的接触力学不考虑物理输入变量，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，除其他事项外，通过实验确定的特征图来描述材料失效，绘制了键的切割过程。在目前的研究项目中，特征图是通过在高分辨率VEM模型的帮助下对分离过程进行局部分析来确定的，而不是精心设计的实验活动。具体的材料层属性、材料失效信息和切割工艺参数被纳入到VEM模型中。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、功耗与工艺参数之间的相关性。为了能够利用VEM模型对玉米秸秆的DEM模型中的绑定参数进行标定，在秸秆组织水平和整个秸秆上进行了试验，确定了秸秆的结构力学特性、材料特性和破坏特性。

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.