Research On Durability Life Prediction Of Passenger Car's Steering Knuckle;李 飞

With the rapid growth of automobile production and sales, automotive product quality have become one of the most issues which automobile OEMS and consumers are concerned about.In the the process of automotive development, proving ground durability experiment is commonly used to evaluate the quality of the developing models by automobile OEMS. Durability experiment is the only way to find out the fatigue problems in the designing process, If any fatigue problems have been found out , improvement and optimization will be carried out, then a proving ground durability experiment will be put into practice. Automotive proving ground durability experiment usually lasts several times, so it may postpone the automotive development cycle. During the the process of automotive development cycle, based on the proving ground durability experiment, it will reduce the iteration times of the proving ground durability experiment and shorten the automotive development cycle that using the digitized CAE method to to identify the weak point in the automotive durability design process and to carry out the improvement before the proving ground durability experiment. At present, the life prediction simulation which is based on proving ground durability experiment is one of the traditional vehicle dynamic hotspots in domestic and abroad.Associated with the project of National 863 Program, in this paper , a domestic A0-class passenger car's steering knuckle is used for study, based on target vehicle's durability experiment data measured in hainan automotive proving ground, by making fully use of the combination of experiment and simulation technique, research on the life prediction of target vehicle's steering knuckle for proving ground experiment has been carried out.This thesis is divided into six parts.The first chapter briefly introduces the development of vehicle durability experiment, and the current research situation of the dynamic load simulation and fatigue prediciton based on proving ground durability experiment is also introduced and summaried.By introducing and comparing the several ways of the proving ground durability experiment dynamic load simulation, the advantages and disadvantages of each method have been Summaried; By introducing the method and current research situation of proving ground durability experiment fatigue life prediciton, the difficuties of fatigue life prediction are also illustrated. The first chapter also gives the mainly research contents of this thesis.The second chapter establishes a muti-dynamic vehicle model for the fatigue life prediciton of proving ground durability experiment.According to the research characteristic of this paper and the structure of the target vehicle, and using ADAMS structure based modeling method, the target vehicle model has been established, it is composed of front suspension, rear suspension, steering and tire model. The vehicle model is validated by taking advantage of the ride and handling test data of the target vehicle. The results show that the vehicle model which is established in this paper is Basically correct, it can describe the dynamical characteristics in linear and nonlinear area correctly and accurately. The vehicle model can be used for further study.Based on the durability experiment data measured in hainan automotive proving ground, the experimental program of vehicle proving ground durability experiment is studied in the third chapter. Firstly, the overall program of the measurement platform for vehicle proving ground durability experiment and its major components are introduced. Secondly, the experiment road is also introduced, and the experimental criterion and load status for target vehicle a hundred thousand kilometers proving ground durability experiment are proposed. Lastly, taking advantage of the experimental criterion and measurement platform, the data measurement of the target vehicle proving ground durability experiment is implemented, it will provide correct experimental data for further dynamic load simulation.The fatigue life prediction of a hundred thousand kilometers durability experiment in hainan automotive proving ground of the target vehicle is studied in the fourth chapter. First by studying the fatigue life prediction analysis method, the influence coefficient method is selected as the life prediction approach of the target vehicle's steering knuckle for proving ground durability experiment. Next, the technique of the steering knuckle fatigue life prediction analysis is introduced, and several influence fators of the steering knuckle fatigue strength have been studied intensively. In order to make sure the correction of the dynamic load simulation, the steering knuckle FEM model and the suspension force transmission characteristics are validated, the analysis research of the comparison on several dynamic load simulation method is carried out by using the vehicle model, the body fixed method is choosen and its accuracy for dynamic load simulation is validated. At last, based on the boundary condition load of the target vehicle's steering knuckle which is generated from dynamic load simulation, the FEM analysis software MSC NASTRAN and the fatigue life analysis software MSC Fatigue are used to evaluate the fatigue life of the target vehicle's steering knuckle for proving ground durability experiment, the fatigue cumulative damage of each experimental road for a hundred thousand kilometers proving ground durability experiment is also attained.The life prediction of the target vehicle's steering knuckle for proving ground durability experiment is accomplished by using the proposed steering knuckle fatigue fracture bench scale test in the fifth chapter.First, this chapter has studied the program of the steering knuckle fatigue fracture bench scale test, and the steering knuckle separate loaded program is validated to execute the steering knuckle fatigue fracture bench scale test. The experiment is executed, and the FEM method is used to simulate it. By comparing the experimental and simulated results, the accuracy of the life prediction of this steering knuckle bench scale test by using FEM method is recognized. Next, based on this experimental program, the steering knuckle residual life bench scale experiment and simulation are executed, the steering knuckle fatigue cumulative damage due to the steering knuckle residual life bench scale experiment is also predicted. At last, the accuracy of the life prediction of target vehicle's steering knuckle for proving ground durability experiment is validated by adding the steering knuckle fatigue cumulative damage caused by proving ground durability experiment and the residual life bench scale experiment.Chapter six summarizes the contents of this paper, and the future research directions are proposed and discussed.For resolving practical issues, the life prediction of target vehicle's steering knuckle for proving ground durability experiment has been studied, and it has creative works following:(1) The vehicle dynamic load simulation method based on automotive proving ground durability experiment data is deeply analyzed. By using the combination method of experiment and simulation, the body fixed loading method is confirmed more accurate for the vehicle dynamic load simulation.(2) By deeply studyed the life prediction of passenger car's steering knuckle for proving ground durability experiment, a complete and regulate fatigue life prediction method of passenger car's part for proving ground durability experiment is proposed, from proving ground durability experiment data collection to dynamic load simulation, to the life prediction and validation of vehicle's part.