| 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. |
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