粘重土条件下残膜与土壤分离机理及捡拾机构优化的研究

Plastic film residue from farmland has seriously affected the production of crops and agricultural sustainable development. It is the inevitable trend of using machine to recycle plastic film residue. In order to solve the problems of wind damage, heavy soil led to low collecting rate and working quality, this project based on the mechanical properties of plastic film residue, establish dynamic model of plastic film residue rupture, obtain function of plastic film residue rupture, reveal the rule of plastic film residue rupture, research mechanical properties of heavy soil, analyze the relationship between the change of mechanical properties of plastic film residue and the soil movements, explore critical condition of separating between film and soil and build mathematic model, reveal separation mechanism between plastic film residue and soil, under the condition of heavy soil , in order to recycle the small plastic film residue in the surface of soil and topsoil, put forward the collecting structure which is the combination of spike tooth and harrow, research the relationship of different ways of combination ,location matching and the rate of collecting , try to make the sample of the machine , conduct the a series of experiments, obtain the relationship of collecting rate and the actuation characteristic and the geometrical parameters as well as the influence, confirm the influence of different factors to the collecting property , optimize structure and parameter , seek the optimal combination of parameter. The successful implementation of this project can lay the foundation for the research and development of the residual film machine.

农田残膜污染已严重影响作物的产量和农业可持续发展，机械化回收残膜是必然趋势。为解决新疆残膜因风化破损断裂严重及粘重土壤致使捡拾率低、作业质量差等难题，本项目在研究残膜力学特性的基础上，建立残膜断裂的动力学模型，获取残膜断裂函数，揭示残膜破损断裂规律；研究粘重土壤力学-流变特性，分析捡拾机构与残膜有效接触后残膜力学性能变化与土壤运动轨迹的关系，探索残膜力学特性范围内残膜与土壤分离的临界条件，构建残膜与土壤分离数学模型，揭示残膜和土壤分离机理；在粘重土壤条件下，为回收土壤表面及耕层内的碎片残膜，提出摆动式钉齿与链齿耙式相结合方式的捡拾机构，研究不同组合方式、位置匹配与捡拾率间关系，试制物理样机，开展试验研究，获取捡拾率与机构驱动特性、结构几何参数之间的关系及其影响变化规律，确定各因素对捡拾性能的主次关系，优化结构和工作参数，寻求最优参数组合。本项目的成功实施为残膜高效回收机械研发奠定基础。

地膜覆盖技术在农业生产中应用广泛，新疆因自然条件恶劣，导致地膜风化残留于土壤中造成严重的减产现象，亟需提高残膜回收质量。项目针对粘重土壤粘性大、流动性差、现有的残膜回收方式作业质量差等难题，开展了残膜在粘重土壤中的分布规律与力学特性、土壤与残膜的分离机理、残膜捡拾机构优化研究，并分析膜土分离技术研制残膜回收机。对春季播种前和秋季收获后的田间残膜分布进行测量，确定土壤深度5-10cm的残膜含量较多。使用万能材料试验机对不同深度、不同捡拾期的残膜进行抗拉强度、延伸率及最大拉断力特性实验，建立残膜断裂的动力学模型，得到残膜断裂函数与断裂规律。通过离散元分析软件仿真机具在粘性土壤中的工作状况，分析残膜捡拾装置与土壤接触的瞬态力学行为，确定弹齿土壤工作过程主要受力为前进过程中土壤给予的阻力。设计了链耙式残膜回收机，解决现有拾膜装置难以有效分离和回收粘重土壤中残膜的问题；该机通过链耙部件将起膜铲所铲出的膜土物料进行首次膜土分离，同时抖动机构使输送链持续抖动以便于膜土物料的破碎，筛选后的混合物进入振动部件进行二次筛选，实现膜土分离；分析链耙部件上任意位置混合物的运动情况，确定链耙部件作业倾角为39°；通过探究耙齿的运动轨迹，采用双排双勾单列的方式进行安装；在输送链将膜土物料向后输送过程中增加抖动机构，提高膜土分离的效果；分析膜土物料在筛面上沿进程工作时跃起的受力状态,设计栅条型筛面连杆振动机构进行膜土再次分离，提高残膜回收效率；应用链传动及连杆的驱动方式实现拾膜、脱膜的传动需求，能在恶劣的工况下作业，工作效果稳定且维修周期长。通过田间正交试验验证机具的可靠性与作业效果，结果表明链耙式残膜回收机能有效回收粘重土壤耕层中的残膜，并获得最优工作参数组合：前进速率为1.3m/s、入土深度为117mm、输送链驱动轮转速为65r/min，在该工作参数组合下将粘重土壤中残膜的回收率从65%提高至85%。