基于FEM-SPH耦合的卷辊式耕层残膜回收部件结构优化与试验

    Structural optimization and test of the roll type tillage residual film recovery components using FEM-SPH coupling

    • 摘要: 针对棉田耕作层内残膜力学性能差及膜土分离困难,残膜拾净率低和回收的残膜含土量高等问题,该研究对卷辊式残膜回收部件进行优化。在分析起膜捡膜工作过程和建立卷辊弹齿与膜土团聚体之间动力学关系的基础上,采用有限元法(finite element method,FEM)和光滑粒子流体动力学(smoothed particle hydrodynamics,SPH)耦合算法,建立卷辊弹齿-膜土团聚体接触计算模型,探究卷辊弹齿与膜土团聚体之间相互作用机理,分析卷辊弹齿接触膜土团聚体后残膜受力程度和土壤扰动程度的变化规律。以卷辊回转半径、弹齿直径、弹齿顶端折弯角为试验因素,以残膜平均峰值应力及土壤最大应变为指标开展仿真试验,分析各因素对指标的影响规律并对卷辊弹齿结构参数进行优化,获得卷辊弹齿最优结构参数为:卷辊回转半径100 mm、弹齿直径5 mm、弹齿顶端折弯角42°,此时残膜平均峰值应力为0.1201 MPa,土壤最大应变为3.7584。为了验证优化后卷辊弹齿的捡拾作业性能,以拾净率和含土率为试验指标进行田间试验,结果表明:机具拾净率为80.34%,含土率为37.13%,与初代研制的样机相比拾净率提升了8.74个百分点,含土率下降了12.18个百分点,机具作业性能明显提升且试验指标达到设计要求。本文建立的有限元模型可为残膜回收机关键部件的结构优化提供参考。

       

      Abstract: Residual film recovery is highly required for the high mechanical properties and picking-up rate with the low soil content of the recovered residual film. In this study, a roll-type picking component was designed to easily separate the soil. The rotary tillage blade was also used to throw up the membrane-soil agglomerate. The roll spring teeth were then selected to effectively pick up the residue film. The finite element method (FEM) and smoothed particle hydrodynamics (SPH) were coupled to establish the contact model between the roll spring teeth and the membrane-soil agglomerate. The finite element meshing was performed on the roll spring teeth and the residual film. The soil was assumed to the smooth particles. A microscopic analysis was made on the residual film stress and soil disturbance after the roll spring teeth were contacted on the membrane-soil agglomerate. It was found that the residual film stress was concentrated near the contact tip point of the roll spring teeth. The peak stress of residual film increased first and then decreased with the increase of the contact time. The maximum and average peak stresses of residual film were 0.2518 and 0.1319 MPa, respectively. The soil strain increased gradually with the increase of contact time, where the maximum soil strain was 3.271. The soil particles near the tip of the roll spring teeth were cracked to increase the soil disturbance. A three-factor five-level quadratic regression was conducted with the turning radius of roll, the diameter of spring teeth, and the top bend angle of spring teeth as the test factors, while the average peak stress of residual film and the maximum soil strain as the test indexes. A mathematical model was also established to clarify the influence of each influencing factor on the test indexes. At the same time, the optimal structure parameters of roll spring teeth were obtained as the roll turning radius was 100 mm, the spring teeth diameter was 5 mm, and the top bend angle of spring teeth was 42°. In this case, the average peak stress of residual film was 0.120 1 MPa, and the maximum soil strain was 3.758 4. The roll spring teeth were then fabricated using the optimal structural parameters after simulation. A new machine of residual film recovery was assembled to verify the influence of structure parameters of roll spring teeth on the picking-up performance. Field verification tests were conducted with the picking-up rate and soil content as the test indexes. A better performance was achieved in the picking up rate of 80.4% and soil content of 37.13%. There was no slip on the high-speed rotating of roll spring teeth. The residual film was constantly wound and indirectly punctured at the tip of the teeth. The roll spring teeth made it easier to crack the soil in the membrane-soil aggregate. The soil was then much easier to leave the residual film. The membrane-soil separation was gradually completed, indicating the soil no longer sticking to the residual film. Compared with the previous soil tank test, the picking-up rate increased by 8.74 percentage points, whereas, the soil content decreased by 12.18 percentage points, indicating the better performance of the machine. The finite element model can provide a strong reference for the structural optimization of the residual film recycling machine.

       

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