基于多特征综合分析的农用残膜柔性离散元模型构建方法

Construction Method of Flexible DEM Model for Agricultural Residual Film Based on Multi-feature Comprehensive Analysis

摘要:

由于缺乏柔性薄膜离散元模型构建方法，对薄膜类物料在机械装置上运动特性的模拟研究受到限制，提出了一种基于柔性变形特性、摩擦特性及空气动力学特性的多特征综合分析的薄膜类物料离散元模型构建方法，以农用塑料残膜为例对其有效性进行了评价。通过物理试验测得单片塑料残膜悬垂系数、静摩擦因数、摩擦角、动摩擦因数及悬浮速度分别为0.397、0.417、22.636°、0.373及2.327m/s。利用Rocky仿真软件的Shell模型建立了残膜离散元模型，以悬垂系数、摩擦角及悬浮速度为响应指标，采用因子筛选试验、最陡爬坡试验和中心组合试验确定最佳参数组合为：基本壳体单元面积174.017mm2、弹性比0.850、密度238.583kg/m3、杨氏模量5.676MPa、膜间静摩擦因数0.437和膜间动摩擦因数0.397。最后，通过残膜料群流动试验开展了模型可靠性验证。结果表明，残膜料群悬浮速度模拟值与物理值相对误差为3.18%，吻合较好；残膜料群在气流作用力、膜间摩擦力及重力作用下表现的团聚迁移、悬停、膨胀松动及料群解体等动态行为与物理试验结果一致，证明了建立的残膜柔性模型具有可行性和适用性。

Abstract:

Due to the lack of film model construction methods, the motion characteristics numerical simulation of the flexible materials on mechanical equipment is limited. A flexible model construction method based on a multi-feature comprehensive analysis of deformation, friction and aerodynamic characteristics was proposed, and its reliability was verified by using the plastic film as a study case. Firstly, the drape coefficient, static friction coefficient, friction angle, dynamic friction coefficient and suspension velocity of the film were measured to be 0.397, 0.417, 22.636°, 0.373 and 2.327m/s, respectively, by physical tests. Based on this, a film model was constructed by using the custom shell model of Rocky software. Taking the drape coefficient, friction angle and suspension velocity as the response indexes, the optimal parameter combination of the model was determined as the basic shell element area of 174.017mm2, elastic ratio of 0.850, density of 238.583kg/m3, Young’s modulus of 5.676MPa, film-film static friction coefficient of 0.437, and film-film dynamic friction coefficient of 0.397. Finally, the film group flow test was conducted to verify the general applicability of the model. It showed that the relative error between the simulated suspension velocity and the physical value was 3.18%, and the behaviour of migration, suspension, expansion loosening and disintegration were consistent with the physical test, indicating that the flexible model has feasibility and applicability.