基于非线性接触的杆齿式拾膜、卸膜机构工作机理研究

Collecting plastic film residue and waste by used rod shaped tooth agricultural equipments exhibits some difficulties such as low reliability during operation, problems with releasing film and low efficiency in collecing edge film. This project aims at the study of mechanical dynamics and working mechanism of non-linear contact for mechanical equipments that are used for collecing/releasing plastic film residue and waste agricultural fields. The project intends to carry out studies on the separation mechanism between plastic film and hardening soil, and design the lifting mechanical device with edge film by experimental tests and analysis of the plastic film's mechanics properties, it will establish a non-linear contact dynamics model for the rod shaped teeth device when interacting with film-soil or with film only, and explore the mechanism of the rod shaped tooth's movement when collecing and releasing plastic film by utilizing the multi-physical field coupling function between the rod shaped teeth and film-soil or between the rod shaped teeth and plastic film. The project integrates various techniques such as contact dynamics, non-linear finite element method, numerical analysis and complex surface modeling, and combining theorical analysis, bench experiment and field test/evaluation, which therefore has both theoretical and practical significance. The project is expected to help establishing an adanced design theory and improve the design standard of the rod shaped tooth agricultural equipments for recyling plastic film residue and waste. The scuccess of this project will therfore contribute to popularizing and spreading the technology of recyling plastic film redidue and waste in argoricultural field and to facilitating production of commerical recycling equipments.

本项目针对目前使用的杆齿式残膜回收机具存在工作可靠性低、卸膜难度大以及无法有效回收边膜等问题，研究杆齿式拾膜、卸膜机构的非线性接触动力学模型和工作机理。本项目在对不同厚度、不同使用时间的残膜物理力学特性进行分析与测试的基础上，研究边膜与其上板结覆土的分离机理，设计起边膜装置；以地膜-土壤、单一地膜为作用对象，建立杆齿在拾膜、卸膜过程中与地膜-土壤、地膜间非线性接触动力学模型；探索拾膜、卸膜杆齿与地膜-土壤复合模型或与单一地膜模型间的多物理场耦合作用，研究拾膜、卸膜的运动机理。本项目融合了接触动力学、非线性有限元方法、数值分析和复杂界面建模技术，将理论分析、台架试验和田间测试验证结合，不但有重要的理论价值，更有广泛的应用前景。本项目的研究有助于建立杆齿式拾膜、卸膜机构的设计理论，提高残膜回收机具的设计水平，从而促进残膜回收技术的推广和先进残膜回收机具的产业化生产。

残膜回收技术对解决我国覆膜种植地区农田和环境的污染、保证农业的可持续发展至关重要。由于缺乏残膜的物理特性、土壤粘着特性的研究，目前的各种残膜回收机具等存在无法有效回收边膜以及拾膜、卸膜机构工作可靠性低、卸膜困难的问题。针对上述问题，在国家自然科学基金项目“基于非线性接触的杆齿式拾膜、卸膜机构工作机理研究”的支持下，本课题在对不同厚度、不同使用时间的残地膜力学特性研究与测试的基础上，开展杆齿式残膜回收机具拾膜、卸膜过程中非线性接触动力学研究。主要完成内容如下：. (1) 对不同厚度、不同铺膜时间的残地膜的拉伸负荷和断裂伸长率等力学性能进行了测试和分析，获得了农用地膜厚度、使用时间与抗拉强度、延伸率等力学性能的关系以及地膜厚度、使用时间和拉伸方式对残地膜力学性能影响的显著性。. (2) 研究板结土壤内聚力以及板结土壤—地膜结合力，利用组合式建模法建立地膜-土壤、板结土壤-深层土壤的复合模型；分析了圆盘碎土性能，建立圆盘碎土过程的非线性接触有限元模型；当圆盘半径为160mm、机具行进速度为0.85m/s、工作倾角为300时，圆盘碎土装置碎土性能最好。. (3) 分析了拾膜杆齿与地膜、拾膜杆齿与卸膜刮板以及拾膜杆齿与卸膜杆齿的接触关系，建立拾膜杆齿与地膜、拾膜杆齿与卸膜刮板、卸膜杆齿的有限元接触模型进行接触动力学分析，获得各自变形及应力情况，并通过高速摄像试验验证。. (4) 建立杆齿式拾膜、刮板式卸膜机构及摆杆驱动式卸膜机构的运动学、动力学模型，以机构效率最大、接触应力最小等要求为目标，采用多目标模糊优化法优化拾膜机构；利用Adams动力学仿真软件对卸膜机构进行动力学仿真分析，并通过台架试验确定机构最佳参数组合。. (5) 根据优化结果改进杆齿式残膜回收机并制作物理样机，通过多因素正交试验及响应面试验确定机具的工作参数为拾膜齿入土深度为65mm，机具前进速度为1.2m/s，速比为1.0。