新疆棉田秆土膜混合物离散元仿真参数标定

Discrete Element Simulation Parameter Calibration of Cotton Stalk-Soil-Film Mixture in Xinjiang

摘要:

针对新疆棉田地表及浅层秸秆-土壤-残膜(简称“秆土膜”)混合物离散元接触参数缺乏,制约残膜回收装备关键部件仿真分析与参数优化问题,本研究以新疆沙性土壤、棉花秸秆和残膜为研究对象,建立秆土膜混合物离散元模型。针对材料的物理特性,选取Hertz-Mindlin(no slip)与Hertz-Mindlin with Bonding模型分别表征土壤、秸秆、残膜的接触行为与残膜柔性变形的力学特性。通过分体圆筒法测得秆土膜混合物休止角为33.97°,并以休止角为响应指标,基于Plackett-Burman 设计对21 个接触参数进行筛选,确定土壤-土壤静摩擦因数、土壤-土壤动摩擦因数、残膜-钢静摩擦因数、残膜-钢动摩擦因数和秸秆-钢静摩擦因数为主要影响因素。最陡爬坡试验确定参数优化区间后,利用响应面法构建休止角与关键参数间的二次回归模型并进行参数寻优。结果表明:最优参数组合为:土壤-土壤静摩擦因数0.329、动摩擦因数0.114;残膜-钢静摩擦因数0.418、动摩擦因数0.150;秸秆-钢静摩擦因数0.293。采用该参数组合进行仿真验证,得到休止角平均值为35.11°,与实测值相对误差为3.36%。研究结果表明,标定后的参数能够较好表征新疆棉田秆土膜混合物的宏观堆积特性,可为残膜回收机起膜、输送、清杂与卷捆等关键部件的离散元仿真与参数优化提供基础参数。

Abstract:

In view of the lack of discrete element contact parameters of straw-soil-residual film mixture on the surface and shallow layer of cotton field in Xinjiang, the simulation analysis and parameter optimization of key components of residual film recovery equipment are restricted. Xinjiang sandy soil, cotton straw and residual film were taken as the research objects, and a discrete element simulation model suitable for the mixture was constructed. According to the physical properties of materials, Hertz-Mindlin (no slip) and Hertz-Mindlin with Bonding models were selected to characterize the contact behavior of soil, straw and residual film and the mechanical properties of flexible deformation of residual film. The repose angle of the cotton stalk-soil-film mixture was measured to be 33.97° by the split cylinder method. Based on the Plackett-Burman experimental design, five significant influencing factors were selected from 21 contact parameters, which were soil-soil static friction coefficient, soil-soil dynamic friction coefficient, residual film-steel static friction coefficient, residual film-steel dynamic friction coefficient and straw-steel static friction coefficient. After determining the parameter optimization interval by the steepest ascent method, the quadratic regression model between the angle of repose and the key parameters was constructed by the response surface method and the parameters were optimized. The results showed that the optimal parameter combination was soil-soil static friction coefficient 0.329, dynamic friction coefficient 0.114; the static friction coefficient of residual film-steel was 0.418, and the dynamic friction coefficient was 0.150, straw-steel static friction coefficient was 0.293. Using this parameter combination for simulation verification, the average angle of repose was 35.11°, and the relative error with the measured value was 3.36%. The results showed that the calibrated parameters can better characterize the macroscopic accumulation characteristics of the stalk-soil-residual film mixture in Xinjiang cotton field, and can provide basic parameters for discrete element simulation and parameter optimization of key components such as film lifting, conveying, cleaning and baling of residual film recovery machine.