大麻茎秆-往复式切割器交互作用切割机理及高质量切割多参数优化

Hemp, it means industrial hemp in the project, which stalk fiber is featured by hygroscopicity, bacteriostasis and antistatic properties, and thus it is popular with people at home and abroad. During the machinery harvesting, the phenomena, such as stubble breaking and phloem tear, can easily occur in hemp stalks, which can reduce the harvesting quality. Oriented at technical demands during the R&D process of hemp harvesting machines, based on the previous research foundation of applicants, we will seek for the basic and guiding principles for breaking through technological bottlenecks in the project. From the perspective of research on basic principles, we will explore the mechanical physical properties of hemp stalk and mechanical model of composite materials, construct the flexible body model of hemp stalk and rigid body model of cutter, conduct research on the rigid-flexible coupled multibody dynamics model which accurately describe the harvesting process of hemp stalk, explore the mechanism of cutting failure, and finally rearrange and perfect the cutting mechanism of stalk-reciprocating cutter interaction in this project. From the perspective of research on guiding principles, we will design the cutting blade teeth by bionics means, conduct the parametric design on non-standard cutting blades interacted by blade teeth and sliding cutting angles, and establish the multi-index evaluation model in conformity with operation quality actually required by hemp stalk harvesting. In addition, we will also use the multi-type bench cutting test to obtain the cutter geometric parameters, cutting dynamic parameters and planting density parameters for high-quality cutting. At last, we will rearrange and perfect the guiding principles for overall optimization on harvesting parameters in the project.

大麻，项目特指工业大麻，其茎秆纤维具有吸湿、抑菌和防静电等优良特性，受国内外人们的欢迎。大麻茎秆机械收割时易产生破茬和韧皮撕裂的现象，影响收割质量。项目以大麻茎秆收割机械研发过程中的技术需求为导向，基于申请人前期研究基础，寻求突破技术瓶颈的基础性和指导性原理。在基础性原理研究方面，项目将探究大麻茎秆机械物理特性及复合材料力学模型，构建大麻茎秆柔性体模型和切割器刚体模型，研究准确描述大麻茎秆收割过程的刚柔耦合多体动力学模型，探索切割失败现象产生的机理，并整理完善茎秆-往复式切割器交互作用切割机理；在指导性原理研究方面，项目将利用仿生手段设计切割刃齿曲线，参数化设计刃齿、滑切角交互的非标准切割刀片，构建符合大麻茎秆收割实际要求的作业质量多指标评价模型，利用多层次台架切割试验获得高质量切割的切割器几何参数、切割动态参数和种植密度参数，并整理完善收割参数综合优化的指导性理论。

本研究面向大麻茎秆切割部位极易产生破茬和韧皮撕裂的现象，研究解决方法。梳理了大麻收获技术、高效切割技术文献资料，获得了大麻茎秆关键力学特性参数，完成了相关样机对大麻切割-输送作业质量影响参数分析，探索了针对高质量切割的仿生切割器几何参数设计，设计改进了茎秆切割试验台，完成了高质量切割相关作业因素综合影响原理和因素优化，从而系统获得突破关键技术的基础性和指导性原理。发表获得仿生切割器1套，发表相关论文4篇、授权发明专利3件、作学术报告2次、指导研究生1名。项目研究为后续关键收获样机切割器制造提供指导意义，具有一定的应用前景。试验研究具体结果如下：.获得大麻轴向抗压强度17.39 Mpa，模量1197.29 Mpa；径向抗压强度8.38 Mpa，模量50.27 Mpa；切向抗压强度8.21 Map，模量46.43 Mpa；抗弯强度78.43 Mpa。测得大麻单茎秆最大切割力和切割功耗平均值分别为482.7 N和2.46 J。根据仿生学理论，将蝗虫口器上颚作为仿生对象，提取蝗虫上颚轮廓曲线，设计制造仿生刃齿刀片的切割器。自行设计试验台架，通过多因素正交试验，分别考察了刀刃类型、刀片长度（该因素代表滑切角，刀片长度长的滑切角小）和动刀组数对综合评分值的影响情况。获得仿生齿刃刀片、长刀片（120 mm）、往复式双动刀切割器的最优组合。通过正交试验评分值最优的水平组合，对平均切割速度和茎秆喂入速度两组参数连续可调节的因素进行二次回归正交旋转设计试验，研究因素对切割功率、切割质量和综合评分值的影响情况。通过求解回归函数获得最优值。当平均切割速度为0.8m/s、茎秆喂入速度为1.1 m/s时，切割功率最小，为950.4215 W（3次切割总和，即3 m割幅）；当平均切割速度为1.2610 m/s、茎秆喂入速度为0.6725 m/s时，切割失败株数最少，为15.8915株（3次切割总和，3平方米面积）；当平均切割速度为1.1146 m/s、茎秆喂入速度为0.7018 m/s时，评分值最高。综合试验结果，大麻切割最佳切割器和最佳参数为：平均切割速度为1.1146 m/s、茎秆喂入速度为0.7018 m/s，采用往复式双动刀切割器，选用仿生齿刃长刀片（120 mm）。