| There are many different types of transmissions including:Manual Transmission, Automatic Transmission, Continuously Variable Transmission, Automated Mechanical Transmission, and Dual Clutch Transmission, while regardless of what type of transmissions, as the main components in the transmission, the strength and reliability of gears are directly related to the transmission quality, thus affecting the performance of the vehicle.The national standard for calculating gear load capacity includes large numbers of coefficients, the solution of which is very complicated, and the variation of displacement field, temperature field and stress field in the whole gears construction region can not be obtained. The gear fatigue life and permissible stress can just be obtained in gear test, while the stress and temperature in the process of gears rotating can not be directly measured. In order to ensure gears are not destroyed, gears have to be conservatively designed. With the rapid development of computer and software technology, as a numerical analysis method applied widely, finite element method has been applicable to the design and analysis of gears. The application of the method can not only achieve gear contact bending and scuffing load capacity, but also optimize gear tooth profile and design light-weighted gears.The research has been supported by the National 863 High Technology Research and Development Plan Key Project (2006AA110101) and the Technology Development Program of Jilin Province (20076029). According to characteristics of the automotive industry, the classical method and the finite element method for load capacity of transmission gears were studied. By analyzing a certain type of actual transmission, the appropriate processes and norms were explored.Firstly, the study compared the advantages and disadvantages of various types of transmissions, automobile transmission gears background and significance, and the gear load capacity status at home and abroad were analyzed. Three common gear failure modes:flanks spalling (pitting), breakage, and scuffing were reviewed and analyzed. Main contents in this dissertation were described as follows.Oriented engineering application, factors including load factors, nominal stress factors, permissible stress factors, and stress formulas used for calculating stress and permissible stress in gear contact and bending load capacity standard GB/T 3480-1997 were systematically analyzed and summarized. Computer program modules for analyzing gear contact and bending load capacity were developed by using APDL, which was conveniently applied, and provided necessary basis for validating the results of the finite element model for analysis of gear contact and bending load capacity.Oriented engineering application, basic parameters, flash temperature and its factors, integral temperature and its factors, flash temperature scuffing risk and integral temperature scuffing risk in scuffing load capacity of flash temperature method standard GB/Z 6413.1-2003 and integral temperature method standard GB/Z 6413.2-2003 were systematically analyzed and summarized. Computer program modules for analyzing gear scuffing load capacity were developed by using APDL, which could predict the temperature of the engaging gears quickly and accurately.Corresponding to the research of the finite element method for analyzing gear contact and bending stress in the engagement gears and the development of relevant computer program modules, parametric three-dimensional model was developed for the finite element analysis on contact, bending, and scuffing. The contact finite element model of meshing points, the bending finite element model for meshing gears on different locations, gear tooth profile and the rotation were developed. Oriented engineering application, parametric geometric model for gears and computer program modules for automatically building contact and bending finite element models in meshing gears were developed by using APDL.The fundamental parameters of the finite element model for the analysis of gear contact temperature were made a research. By analyzing the theory of the gear contact temperature, the boundary conditions of the analysis of gear contact temperature and the moving heat load changing with the time and location were developed. The method of moving heat load in ANSYS was proposed. Computer program modules which could analyze the finite element model of gear contact temperature were developed to predict the profile of the gear temperature condition accurately by using APDL.Finally, in accordance with characteristics of the automotive industry and the need of reversal design of transmissions, the automatic finite element model was developed and applied. Moreover, aiming at the problem in analyzing load capacity of transmission gears, the load capacity of transmission gears in terms of contact, bending and scuffing was studied and analyzed.The creative contents in this dissertation are:(1) Oriented engineering application, the national standards were analyzed and summarized as follows:gear contact and bending load capacity of standard GB/T 3480-1997, scuffing load capacity of flash temperature method standard GB/Z 6413.1-2003 and integral temperature method GB/Z 6413.2-2003. By using APDL, computer program modules which could analyze the load capacity of gear contact, bending, flash integral and temperature integral were developed. Just applying the original datas of gear load capacity, the analysis of gear load capacity could be automatically completed. This method could not only improve efficiency and accuracy, but also avoid the errors caused by using simplified formulas or charts.(2)Based on the geometric relationship among gears, the finite element model of main meshing points for the engagement gears was developed in order to make a comprehensive analysis of gear contact states in the process of gears meshing. The most important question determined by the gear contact line and the load in the finite element model of gear bending was considered. According to the load distribution principle of helical gear contact line, the convenient method for engineering application to determine the contact line and the load assumptions for gear bending finite element model was put forward, which could not only be appropriate for meshing gears on different locations, gear tooth profile and the rotation, but also solve the problem of the face load and transverse load in the process of multi-tooth gears meshing.(3) Gear tooth average heat transfer coefficients, the average single gear tooth heat flux and their determination methods were proposed, which could avoid the weakness of using constant heat transfer coefficients and heat flux, making the results more close to the real distribution of gears temperature. Through the research of the tooth heating and the mechanism of transient temperature, the friction heat continuously varying during gears meshing was converted into a mobile function of heat load changing with time and location. The method dealing with loading moving heat function was proposed in ANSYS, which not only solved flash temperature on gears teeth, but also made a significance in solving various types of moving load function problems.(4) By using APDL, computer program modules for automatically building parametric gear solid geometry model, contact and bending finite element model corresponding to the process of gears meshing and contact temperature finite element model were developed. Just applying the original gear datas, the analysis of gear loading capacity could be automatically completed. Combined with the reverse design of a transmission and the computer program modules for classical analysis, the integration of classical analysis and finite element analysis of transmission gears contact, bending and scuffing load capacity was fulfilled, and the lack that only a certain load capacity could be analyzed in the past was overcame.
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