（通讯员 杜俊）近日，我校工学院夏俊芳教授课题组研究成果以“Investigation of the burial and mixing performance of a rotary tiller using discrete element method”为题在Soil and Tillage Research发表。研究建立了粘性土壤的颗粒力学模型，揭示了旋埋刀辊对粘性土壤的扰动过程，为长江中下游水旱轮作区秸秆还田机具作业性能优化提供了新思路。
该研究基于离散元法建立粘性土壤颗粒力学模型，针对粘性土壤离散元法建模过程中输入参数及接触模型难以确定的问题，本研究基于土槽试验对粘性土壤颗粒输入参数的敏感性进行分析，对最敏感参数进行单一标定；对比不同粘性接触模型仿真效果，建立了粘性土壤的离散元法模型；通过提取不同深度土壤颗粒微观迁移特性，研究了旋耕刀和螺旋横刀对土壤的扰动形式、范围及强度，获取了刀具不同工作参数及结构参数下的土壤扰动过程，分析了刀具扰动特性的影响因素。研究表明，HM-JKR模型（Hertz-Mindlin contact model with JKR）对粘性土壤的模拟更符合旋耕作业时的土壤形态；作业参数方面，耕深对刀具扰动特性影响最显著，当耕深由150mm增加到180mm时，旋耕刀和螺旋横刀对土壤的平均扰动强度分别提高25%和30%；结构参数方面，旋耕刀正切刃结构、旋耕刀数量及间距是优化旋埋刀辊扰动性能的关键。该研究为优化长江中下游水旱轮作区秸秆还田机具作业性能提供了新思路。
Rotary tiller is a widely used tillage tool in China, and its burial and mixing ability determine its performance. Discrete element method (DEM) is a promising numerical method to study the soil-tool interaction, and a suitable contact model is required to obtain a reasonable accuracy. In order to investigate the burial and mixing performance of a rotary tiller consisted of rotary blade and spiral horizontal blade in silty clay loam, two cohesion contact models HM-B and HM-JKR were compared. The sensitivity analysis for HM-B and HM-JKR were conducted by Plackett-Burman test. The bonding stiffness of HM-B and the surface energy of HM-JKR were the most sensitive parameters for their contact model, respectively, and were calibrated to compare their simulation performance. HM-JKR obtained a relatively smaller error on torque compared with measurement results in a soil bin test. The tillage characteristics of rotary blade and spiral horizontal blade were studied, and the effect of working conditions and rotary tiller structures on these were investigated by simulation. The distribution ratio and the disturbance intensity were selected to evaluate the burial and mixing performance. Compared with rotary blade, the spiral horizontal blade obtained a larger disturbance area and intensity. Tillage depth had the most significant effect on the tillage characteristics. The average disturbance intensity of rotary blade and spiral horizontal blade increased nearly 25% and 30% with the increase of tillage depth from 150 mm to 180 mm. The L-bend structure of the rotary blade was important to the burial and mixing performance of rotary tiller. A reasonable number of rotary blade group in the rotary tiller and distance between each rotary blade group can obtain a satisfied burial and mixing performance with a relative low torque consumption.