Authors

Abstract

In order to simulate straw cutting process, this paper established a maize straw cutting model with discrete element method (DEM) based on straw cutting experiment. Firstly, maize straw model consisting of several small particles was established by DEM. Then, a straw cutting experiment was conducted and the maximum straw cutting resistance was 199 N for straw with 15 mm diameter. Then, single-factor experiment was conducted to analyze the effect of DEM parameters on straw cutting effect and the max straw cutting resistance Fmax. The normal stiffness between particles and blade (ball-facet-kn) and shear stiffness between particles and blade (ball-facet-ks) were found to be the significant factors affecting Fmax, and the value of the parameters that has no significance was determined. The optimum combination of the significant parameters was 17662 N·m-1 of ball-facet-kn and 52499 N·m-1 of ball-facet-ks. The verification test results showed that the maize straw model was cut off, thus it could simulate the real straw cutting effect, and the relative error of max straw cutting resistance Fmax between the simulation and the experiment was below 9.1%. Thus, it could be concluded that the established maize straw cutting model was accurate and reliable.

Abstract in Chinese

玉米秸秆切断是秸秆粉碎还田、少免耕播种等作业中重要的技术环节之一，对玉米秸秆进行离散元建模及参数标定，有利于更好地理解分析玉米秸秆切断行为。本文首先利用万能材料试验机进行秸秆切断试验，测得秸秆最大切断力。其次通过单因素试验，分析不同离散元模型参数对玉米秸秆切断效果及最大切断力的影响，筛选出对玉米秸秆模型最大切断力有显著影响的参数为颗粒墙体间法向刚度ball-facet-kn与切向刚度ball-facet-ks，并确定了其他非显著因素的值。通过最陡爬坡试验确定了这两个关键参数的最优区间，在此基础上，根据中心旋转组合试验建立了最大切断力与显著性参数的二阶线性回归模型。通过Design-Expert优化模块，以最大切断力为目标，得出显著性参数的最佳组合为：颗粒墙体间法向刚度和切向刚度分别为17662 和52499 N·m-1。最优参数组合验证试验表明，秸秆模型和秸秆颗粒之间粘结键被从中间切断，所校核参数模型可模拟真实切断效果，且不同直径秸秆最大切断力仿真值与试验值误差不超过9.1%，所建立秸秆模型准确可靠。研究结果可为少免耕播种、秸秆还田中玉米秸秆切断过程研究提供参考。