As the main component of the tractor gearbox, the box has the functions of shifting operation and carrying the cab, it also carries part of the framework function. If the strength, stiffness, or vibration characteristics of the box do not meet the allowable requirements, large vibration and noise may occur, and even there is the possibility of fracture in some limiting conditions. To solve this problem, according to the structural parameters of a gearbox, the three-dimensional model of the box was established by using the three-dimensional modeling software Creo. According to the dangerous degree of the transmission load when the tractor is working normally, three vehicle working conditions are selected: a round of suspension conditions, farm tool lifting conditions, and emergency turning conditions. In addition, according to the transmission ratio of each gear meshing inside the gearbox, two gear conditions are selected: gear condition one and reverse gear condition one. The forces of the box under these extreme conditions are analyzed. The static analysis and modal analysis of the tractor gearbox are carried out by using the Static Structural module of ANSYS Workbanch. The deformation, equivalent stress distribution, and modal vibration frequency of the gearbox are tested. The topology optimization method is used to improve structural defects and reduce box quality. The results show that the weight of the optimized box reduces by 8.44%, the deformation decreased by 15.89%, and the equivalent stress decreased by 18.34%. The strength and stiffness of the box are improved, the quality is lightweight, the waste of resources is reduced, and the heat dissipation performance and fracture resistance of the box are enhanced.
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