Durability Analysis And Optimization Design Of Key Parts Of Gear Shaft System Of Automobile Transmission

With the rapid growth of automobile popularity,consumers pay more and more attention to automobile safety performance,and the development cycle of automobile is also sharply compressed.Under this background,as one of the most important driving mediums of automobile,the automatic parameter optimization design of transmission gear has become the key to improve the reliability of transmission and even the whole vehicle.It is also of great significance to improve the safety performance of transmission and even automobile by studying the contact stress and strain of transmission bearing to ensure its safe and reliable operation.In this paper,the evaluation method of gear performance including gear durability and usability performance is studied,and the important performance evaluation indexes in gear optimization design are summarized.On this basis,taking improving gear durability as the optimization goal and ensuring gear usability performance as the constraint condition,the mathematical model of multi-objective optimization design for macro parameters of automobile transmission gears is established.In view of the limitations of nsga-iii algorithm in high-dimensional multi-objective optimization,this paper proposes an modified genetic algorithm: introducing a totally ordered mechanism of forced association with reference points and "elimination of challenge arena",which makes the performance of the algorithm not affected by the increase of target number;proposing an elite selection strategy based on the unified measurement of population convergence and distribution,which makes the convergence and distribution of population both considered in the evolution;in addition,an adaptive genetic operator based on evolutionary generations is proposed to improve the optimization speed of the algorithm,aiming at the problem of computing efficiency degradation caused by the "challenge elimination" mechanism.Finally,the multi-objective optimization mathematical model of transmission gear parameters is solved based on the modified genetic algorithm on the platform of scientific calculation software MATLAB.Compared with the optimization result of nsga-iii algorithm,the final optimization result is 4.1% higher in GD index and 86.8% higher in IGD index.It shows that the modified genetic algorithm can greatly improve the distribution uniformity of the population while keeping the convergence of the population similar.In the aspect of contact mechanics analysis of transmission bearing,this paper first discusses the basic equation of Hertz contact theory,and uses the numerical solution method of Hertz point contact problem to calculate the maximum contact stress of deep groove ball bearing of different gears of transmission.The errors between the calculated results and commercial software results are less than 1%.The classical Hertz line contact theory puts forward many assumptions,and its application in practical engineering has great limitations.The contact mechanics analysis of the roller bearing of gearbox belongs to the non Hertz contact problem.In this paper,based on the onedimensional simplification of the finite line contact problem,according to the conditions of deformation coordination and force balance,the mathematical model of the whole contact analysis is established,and the numerical solution program is compiled with MATLAB.The solution of the contact stress of the cylindrical roller bearing of different gears of the transmission is completed by iteration.The errors between the calculated results and the commercial software results are less than 4%.This paper standardizes the automatic optimization design process of gearbox gear parameters,proposes an modified multi-objective genetic algorithm,which improves the efficiency of gear parameter design and the quality of gear design.At the same time,the non Hertz contact theory is used to solve the bearing contact problem,which improves the accuracy of the bearing contact mechanical analysis of gearbox.This paper provides a reference for the design and performance verification of the key parts of the gearbox gear shaft system.