多种材料与不同含水率土壤的离散元接触参数标定

Calibration of Discrete Element Contact Parameters for Various Materials and Soils with Different Moisture Content

现有土壤与触土部件材料间的接触参数适用范围较窄,难以模拟高含水率下的作业状况。为了探索多种材料与不同含水率土壤的粘附情况,更加准确地解决触土部件与土壤的粘附问题,以南方稻茬田土壤为研究对象,应用EDEM中的Hertz-Mindlin with JKR Cohesion模型,对不同含水率的土壤与45号钢、超高分子量聚乙烯(ultra-high molecular weight polyethylene, UHMWPE)、聚四氟乙烯(polytetrafluoroethylene,PTFE)的接触参数进行标定。在前期试验的基础上,以碰撞恢复系数、静摩擦系数、滚动摩擦系数和JKR为试验因素,土壤的滚动距离为试验指标设计了Box-Behnken四因素三水平试验。最后对所得回归模型进行优化,得到了含水率21%、26%、31%(±1%)的土壤与45号钢、UHMWPE、PTFE的碰撞恢复系数、静摩擦系数、滚动摩擦系数以及JKR的最优参数。仿真滚动距离与实测滚动距离的最大相对误差为3.46%,说明标定的参数准确可靠,可以为触土部件在进行减粘脱附设计时提供参考。

The applicable range of contact parameters between existing soil and touching soil component materials is relatively narrow,making it difficult to simulate operating conditions under high moisture content.In order to explore the adhesion of various materials to soil with different moisture contents and more accurately solve the adhesion problem between touching soil components and soil,this article took southern stubble soil planting rice as the object,and used the"Hertz Mindlin with JKR Cohesion"model in EDEM to calibrate the contact parameters of soil with different moisture contents and 45#steel,ultra-high molecular weight polyethylene(UHMWPE),polytetrafluoroethylene(PTFE).On the basis of previous tests,Box-Behnken four factor and three level tests were designed with impact restitution coefficient,static friction coefficient,rolling friction coefficient and JKR as test factors and soil rolling distance as test indicators.Finally,the regression model was optimized,and the optimal parameters of collision coefficient of restitution,static friction coefficient,rolling friction coefficient and JKR of soil with 21%,26%,31%(±1%)moisture content and 45#steel,UHMWPE,PTFE were obtained.The maximum relative error between the simulated rolling distance and the measured rolling distance was 3.46%,indicating that the calibrated parameters were accurate and reliable,and provided reference for the design of touching soil components in reducing adhesion and detachment.