The Design Of Plot Wheat Breeding Threshing Machine And Research On It’s Low Damage Characteristics

In the threshing course, there is a big problem of mechanical damage for breeding wheat grain. The damage mechanism of the breeding wheat were studied, and the mechanical properties of breeding wheat were analyzed by finite element method. And then the generation and propagation mechanism of cracks in wheat grain from macroscopic and microcosmic perspective is analyzed. According to the research conclusion, the threshing device of the plot wheat breeding threshing machine is optimized improvement. Finally the experimental study of overall performance is carried out. The main research of the paper is as follows:(1) A plot wheat breeding threshing machine is developed. According to the requirements of breeding wheat grain threshing method and agricultural technology, a plot wheat breeding threshing machine is developed through theoretical analysis and the design calculation of major working parts. This machine is mainly composed of feeding device, threshing device, transmission device and separate cleaning device, etc. The wheat threshing machine can realize a high degree of seed threshing and no seed retention, and it moves more easily. It increased the harvest of wheat breeding work efficiency and reduced labor intensity of breeding work.(2) The study analyzes the threshing process of wheat spike and the damage mechanism of grain. By the CMT2502 type electronic universal testing machine,breeding wheat is carried out the grain husk shell tension test, the compression damage test and shear damage test of grain. The threshing process of wheat head and damage mechanism of wheat grains is analyzed and studied, the results showed that the wheat glume in different parts of the cob by the different force. The force required for vertical tension is larger than that of the inclined tension. In the test of damage mechanism in wheat grain, the moisture content of breeding wheat grain, placement, varieties had quite an effect on its mechanical properties.(3) The stress distribution and damage state of wheat grains under compressive loading at different locations were analyzed. The geometric model and the finite element model with the measured results for breeding wheat grain were established. The stress distribution of breeding wheat grain was analyzed under different pressing locations and different pressing loads by applying the finite element method. The mechanical properties of breeding wheat grain under different pressing locations and different pressing loads were obtained, which could be provided as mechanical parameters for further studying damage mechanism of breeding wheat grain and optimizing threshing machine. And the breeding wheat grain external injury and internal damage cracks were observed and analyzed, the external damage of wheat grain was mainly in the grain surface, and the internal damage was mainly the internal stress crack. The results show that the position of the macro fracture, the position of the micro crack and the fracture direction are consistent with the finite element analysis. It shows that the finite element analysis method can be used to obtain the mechanical properties of the different parts of breeding wheat grain under compressive loading.(4) The study optimizes and improves the threshing cylinder of plot breeding wheat thresher. To reduce the mechanical damage of breeding wheat and develop the plot ofbreeding wheat thresher threshing cylinder, combined with the damage mechanism of wheat breeding experiment and finite element analysis results of the grain mechanical properties, the breeding wheat thresher threshing cylinder is changed to the nail tooth threshing cylinder for the nail tooth and short rasp bar. Make the threshing roller with high net rate, low damage rate, low impurity rate, etc.(5) The study optimized the design of the threshing machine working parameters.Performance the testing research on plot wheat breeding threshing machine after improved. Operating performance test conducted with feed quantity, rotate speed of cylinder, rotate speed of gettering fan as testing factors, with the threshing total loss rate,the threshing broken rate and the trash content of cleaning rate as evaluating indicators.Combined the orthogonal experiments and applied the comprehensive balance method to obtain the optimum scheme of the whole parameters when operating, which the feed quantity was 0.3 kg/s, the rotate speed of cylinder was 1350r/min and the rotate speed of gettering fan was 1000 r/min. Field test with the optimum combination of operational parameters, the results showed that, the average threshing total loss rate was 0.43%, the average trash content of cleaning rate was 15.03% and the average threshing broken rate was 0.48%, which could meet the demand of plot wheat breeding threshing.