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

Abstract

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.