| The boat-type tractor,invented in 1970 s, has become one of the most important power equipments with its unique advantages in deep mud paddy cultivation of southern China. From then, domestic scholars have been devoted to the study of the boat-type tractor, however the unified theory of the structure design and performance has not been formed, which leads to problems when the boat-type tractor into practical work. In the article the glitch of the exciting boat-type tractor would be started from, and then the research on structural design and optimization of the boat-type tractor chassis structure would be carried on.Based on perusing extensively referenced literature about the boat-type tractor, soil dynamics and agricultural machinery design, the fracture of the rear axle and the damage of the chassis structure of the exciting boat-type tractor in the working process are researched in this article. Firstly, the basic chassis structure and transmission system of the boat-type tractor are analyzed. Secondly, multi-excitation modal analysis is used to test the dynamics characteristic of the load-bearing structure of the boat-type tractor chassis based on the basic theory of modal analysis after analyzing the damage of the boat-type tractor. Thirdly, improve the thickness of the chassis load-bearing structure according to the result of the research.In order to obtain excellent performance of boat-type tractors, a separable new boat-type tractor is designed on the basis of previous study. Strength and vibration characteristics are obtained through static analysis and modal analysis on the chassis load-bearing structure. The performance of the new boat-type tractor chassis structure is evaluated combined with the characteristics of the structure of the boat-type tractor, according to the results of static and dynamic analysis.After that, multi-objective optimization design is conducted on the established separable boat-type tractor chassis load-bearing structure on the strength of sensitivity theory. The target, response and design variables of the optimization are designed by related analysis according to the design process. After all this, non-inferior solution in a certain rang is obtained after accomplished the analysis and optimization of the structure by using solver. At last, the optimal design scheme from the non-inferior solution is selected by adopting fuzzy matter-element method and entropy-weight method. Comparative analysis on chassis structure before and after optimization design showed that the optimized boat-type tractor chassis load-bearing structure has good dynamic performance and meet the stiffness requirement.On the basic research of the existing boat-type tractor chassis structure, a new boat-type tractor chassis structure is designed, and the research of the dynamic characteristics, structural optimization, performance verification on the load structure of the boat-type tractor chassis makes the new boat-type tractor does well in field experiment. At the same time, the achievements in this topic laid a foundation for the reliability and the realization of the standardization design of the boat-type tractor. |
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