【作者】 张凯鑫；

【导师】 张衍林；

【作者基本信息】 华中农业大学 ， 农业机械化工程， 2013， 博士

【摘要】 柑橘是我国重要的水果之一,种植面积和产量均居世界第一位。但因其种植在山地丘陵地区,且成熟期非常集中,加之果园附近人力资源短缺,果品的收获问题导致了人工成本非常高,占到了近一半。为了代替人工劳力,国外研制了多种果园运输机。由于成本、地形等原因,不能够完全适应我国的柑橘生产状况。其根本问题在于,果园运输机的轨道建设成本过高。因此,本文提出了单轨道与橡胶辊摩擦驱动方式,极大的简化了轨道的结构,降低了成本。本文针对橡胶辊和单轨道进行了研究。研究内容包括：橡胶辊单轨道的非线性模型的建立、橡胶辊静态驱动能力的研究、橡胶辊动态滚动过程研究、橡胶辊的模态分析、橡胶辊的疲劳寿命数值计算和摩擦式单轨道果园运输机的设计。主要研究结果如下：1)橡胶辊与单轨道非线性模型的建立通过proe建立橡胶套、齿轮芯和方钢轨道的几何模型,并将其组合成刚柔耦合装配模型。选择橡胶的非线性材料模型Mooney-Rivlin模型用于有限元分析,通过测橡胶的邵氏硬度方法确定材料模型参数：弹性模量E=9.39MPa、泊松比0.47、C10=1.565、C01=0.391。分别选择增强拉格朗日和罚函数非线性接触算法作为有限元接触算法。2)橡胶辊静态驱动能力的研究对橡胶辊静态接触摩擦状态的理论计算,得出最大静摩擦力f与σNN,σM和0有关。通过搭建的游动正压力夹紧和双自由度相向扭矩施加方式的试验台进行试验研究,得出了附着面积、压缩量、摩擦力与正压力的关系曲线。基于ansys,利用非线性Mooney-Rivlin模型和增强拉格朗日接触算法进行数值计算,得到了附着面积和压缩量与正压力的关系及接触应力分布、摩擦应力分布和接触状态分布；通过对比,发现仿真正压力对压缩量的关系与实验结果吻合,证明了正压力与摩擦力的驱动性能关系的正确性。结果表明,当正压力为2750N时,单边最大静摩擦力1167N,摩擦系因数0.85,附着面积1909mm2,压缩量4.6mm,达到了果园运输作业的静态技术要求,为橡胶辊的动力执行机构的设计提供了理论基础。3)橡胶辊动态滚动过程研究为了提高橡胶辊的工作性能,使其能够根据驱动力自动调整正压力至合理值,并能均分扭矩、差分转速,设计了将连杆系和锥差轮系作为橡胶辊的动力驱动机构。针对该机构对橡胶辊的影响,利用Abaqus对橡胶辊的滚动过程进行了动力学仿真。仿真中使用Abaqus提供的Mooney-Rivlin模型和非线性接触算法进行数值计算。仿真结果得到了正压力与滚动过程中的功率关系,速度与效率的关系。通过与试验对比,发现正压力对功率的影响与试验结果基本相符。试验表明,该机构作用下橡胶辊效率0.7。结果表明,该机构充分利用了两个橡胶辊的驱动能力,符合自动适应弯道的条件,并在低载状态下节能,提高了橡胶辊在果园运输中的性能。4)橡胶辊的模态分析基于ansys和有限元方法对橡胶辊进行了自由模态分析,并针对实际安装方式进行了约束模态分析。通过POST1后处理工具进行分析,发现自由模态的固有频率与约束模态相近,且有对称模态出现,说明约束方式对于固有频率影响不大。频率范围在1500-1700Hz内。运输机运行时适当避开这段频率,可以减少震动。5)橡胶辊的疲劳寿命数值计算通过Abaqus后处理器,对橡胶辊表面节点的最大主应力时间历程进行提取。对应力时间历程简化、降噪后,利用雨流计数法对橡胶辊表面节点在一个滚动循环周期内进行计数。再通过线性疲劳损伤理论,基于Nsoft软件,对节点进行疲劳寿命计算。结果表明,橡胶辊端面8mm以外节点具有无限次循环次数。疲劳寿命里程最低的点在齿根对应的中间截面处,运行55.8km后将会出现疲劳破坏。6)摩擦式单轨道果园运输机的设计为了降低单轨果园运输的制造成本,提高经济性,第七章设计了一种摩擦式单轨道果园运输机。其结构包括传动系统,摩擦力的正压力加压装置,防侧倒和承重装置等。该运输机驱动力达300kg,额定运行速度1m/s,满足了果园运输的需要。其结构简单,能耗更低。更多还原

【Abstract】 Citrus fruit is one of the major fruit in China with the largest planting area and the highest yield in the world. However, as citrus fruit grows in mountainous and hilly regions, and its maturity is very concentrated, combined with a shortage of human resources nearby orchard, manual costs are very high, accounting for nearly half of the whole cost. In order to replace the manual labor, a variety of orchard transportation machines have been developed in foreign countries. Due to high cost, more complicated terrain and other reasons, those machines are not able to be applied in China’s citrus production.Therefore, a single track with rubber roller friction drive is proposed in this dissertation, which greatly simplifies the track structure and reduces costs.In this dissertation, rubber roller and the single track are studied. The research contents are as following:nonlinear modeling of rubber roller on single-track, study on the static drive capacity of rubber roller, study on the dynamic rolling process of rubber roller, modal analysis of rubber roller, fatigue life calculation of rubber roller and the design of friction single-track orchard conveyor.The main results are as follows.1) nonlinear modeling of rubber roller on single-trackBy using software, namely proe, geometric models of rubber sleeve, gear core and square steel track are established, and they are combined into a rigid-flexible coupling assembly model in chapter two. Rubber nonlinear material model—mooney-rivlin model—for finite element analysis is applied. By measuring the Shore hardness of rubber material, model parameters are determined:the Elastic Modulus E=9.39MPa, Poisson’s ratio0.47, C10=1.565, C01=0.391.2) study on the static drive capacity of rubber rollerBy conducting theoretical calculation to static friction between the rubber roller, it finds that maximum static friction σNN and σM are related toθ. By designing a test-bed measuring by means of floating vertical pressure clamping and double DOF of opposite torque, experiments were conduct which figured out the curves between vertical pressure and bond area&the compression amount&friction. The paper, based on ansys, utilizes nonlinear finite element, Mooney-Rivlin model and augmented Lagrangian contact algorithm in numerical analysis to figure out the relationship between vertical pressure and the adhesion area&the compression amount, the contact stress distribution, friction stress distribution and the distribution of the contact state. The effect of vertical positive pressure on the amount of compression in the simulation test is found by comparison to be in agreement with the result of the experiment test which further verifies the correctness of driving performance relationship between vertical pressure and friction. The statistics show that when the vertical pressure is2750N, the maximum static friction being1167N, the macroscopic friction coefficient0.85, the adhesion area1909mm2, and the compression amount of4.6mm, the orchard transportation meets the requirements of static parameters and provides a theoretical basis for power actuators of rubber roller.3) study on the dynamic rolling process of rubber roller,To improve rubber roller’s performance in rail transportation, making linkage and differential bevel gears train as rubber roller’s power drive mechanism was proposed in this paper at the aim of adjusting vertical pressure automatically to reasonable value according to driving force and achieving torque equalization and differential speed. In this paper, Abaqus was applied to conduct dynamic simulation of rubber roller in rolling process, which was to study effect of the mechanism on rubber roller. In the simulation, Mooney-Rivlin model and nonlinear contact algorithm, both from Abaqus, were applied in numerical calculation. The relation between vertical pressure and power in rolling process and the relation between speed and efficiency were obtained from simulation. By contrast, it was found that effect of vertical pressure on power was basically in line with the experiment results. The experiment indicated that the efficiency of rubber roller was0.7. The results showed that the mechanism can make good use of driving force of two rubber rollers, automatically adapt to curve and save energy in the state of low load, thus improving robber roller’s performance in orchard transportation.4) modal analysis of rubber rollerIn chapter five, the rubber roller’s free modal is analysed by ansys and finite element method, and a constrained modal analysis is conducted for the actual installation methods. By analysing with post-processing tool—OST1, it is found that the natural frequency of the free modal and constrained modal are similar, and there appears symmetrical mode,which shows that constrained methods have little effect on natural frequency. Frequency range is within1500-1700Hz. Conveyor running can properly avoid this frequency and reduce vibration.5) fatigue life calculation of rubber rollerIn chapter six, by abaqus post-processor, the maximum principal stress time history of the rubber roller’s surface nodes were extracted. After realizing stress time history simplification and noise reduction, it uses rain-flow counting method to count rubber roller surface nodes within a rolling cycle. Then, according to the linear theory of fatigue damage and nsoft software, it calculates the fatigue life of nodes. The results show that nodes beyond8mm from the rubber roller end have an infinite number of cycles. The lowest point of fatigue life mileage is at the corresponding mid-section of the tooth root, and fatigue failure will occur when the rubber roller runs55.8km.6) the design of friction single-track orchard conveyor.To reduce manufacturing costs and improve the economy of orchard transportation, a friction single-track orchard conveyor was designed in the chapter seven. By using a transmission system and opponents such as vertical pressure pressure device of friction, rollover prevention devices and burden wheel devices, the conveyor made it possible to produce a driving force300kg and a rated running speed lm/s. Consequently, energy consumption lowered and structure was simple, which met the requirements of orchard transportation.更多还原