| Transmission, as one of vehicle transmission system key components, plays a crucial role on the automobile driving force and speed. As the fast growth of automobile industry, this thesis describes the present status of transmission, and that is serialization, combination and lightweight. Then, it is necessary to put forward the requirements of transmission rapid design and production. In the conditions of assuring transmission reliability, to accelerate the development of new products further, exploring new ways of transmission fatigue life test is of great necessity. Transmission, as a complex system, from system perspective, analyzing combined with parts fatigue condition, has become a new direction. What is more, in practical production, the present effect of traditional time-frequency analysis method is far from perfect. Therefore, it has not been able to satisfy the need of signal dynamic analysis and monitoring in fatigue test. So, on the basis of the fatigue life prediction theory, the statistics analysis theory and vibration signal fault theory, transmission fatigue condition and life prediction are analyzed in this thesis. It is of significance in theory and practice to master transmission fatigue life dynamic characteristics.The main research contents of this thesis are roughly as follows.1) Through condutng finite element simulation analysis and modal test analysis, the low order natural frequencies and corresponding modes of transmission assembly are extracted. The test data is coincided with analytical results, which indicates the reliability of modal parameters. Modal analysis shows the weak position of transmission, which provides a basis for fatigue test. In view of the fatigue damage cumulative theory, by analyzing the relationship between transmission load spectrum and stress cycle times, and the damage degree of key parts with different load strengthen coefficient, a accelerating fatigue test method is put forward. With constant amplitude fatigue contrast test methods, under two test methods, constant amplitude fatigue test method and accelerated fatigue test method, the equivalent relationship of cycle time and damage degree is determined. It can be easily verified that accelerated fatigue test methods keep the correctness of the failure mechanism through contrast test.2) For three series transmissions, concluding triaxial transmission, double countershaft transmission and planetary gear train transmission, fatigue life dynamic test and vibration signal test are conducted. And transmissions fatigue life curve, which is based on kurtosis, mean square amplitude index and sample point number, is established. Combined with transmission fatigue invalidation condition, through analyzing key gear fatigue life curve changes of each transmission, it can be concluded that anti-vibration and impact performance of double countershaft transmission is superior to that of triaxial transmission and planetary gear train transmission.3) On account of cyclostationarity theory, independent component analysis and support vector machine classification, this thesis puts forward comprehensive analysis method for pattern recognition, which is aiming mainly at studying transmission fatigue state, and this kind transmission consist similar transmission structure,but different load. Kurtosis, kurtosis absolute value and kurtosis square are regarded respectively as independent component. By using the classification methods of support vector machine, which include one-to-one, one-to-many and direct constructing multi-class classification support vector classifier, this thesis deals with fatigue life test data of three kinds transmission, and conducts feature extraction and recognition for these data. The testl results show that the test method is correct.4) A dynamic simulation model of gear-shaft-bearing transmission system is established. Then, the dynamic contact stress and the bending stress variation of gear system are analyzed throughout the cycle. Based on the fatigue damage theory and nonlinear critical plane finite element analysis method, transmission fatigue life of every gear is obtained.Taking into consideration the main factors that influence transmission gear fatigue life, material S-N curve is modified in this thesis, and the accuracy of forecast are improved, and fatigue damage cumulative failure area of each gear is forecasted quickly.5) On the basis of fuzzy support vector machine regression theory, kernel function, which is influenced by transmission stress cycle accumulation factor and temperature variation factor, is proposed with transmission fatigue life prediction method. Residual life forecast is realized for every gear of transmission, and the feasibility of the technique is proved through comparing predicted valuel with test value of three kinds of transmission fatigue life.
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