Analysis And Evaluation For Strength Of Automotive Transmission Gears

With the continuous improvement of automotive technology, the demand of the transmission structural strength has become more and more increasingly. As a key component of the transmission, the working conditions of gears are poor and the gears are easy to damage. The quality of gears decides whether the transmission can operate smoothly and efficiently or not. The analysis of gear strength is the basis for the research of the gears carrying capacity, vibration, noise, profile optimization.The common forms of damage are tooth surface pitting caused by contact and tooth broken caused by bending fatigue. As to determine whether the damage occurred, the gear contact and bending strength need to analyze. Using classical method to calculate gear strength, many factors need to calculate, the process is very trouble. It is necessary to normalize and summarize the analysis process, and to develop the gear strength analysis professional module. The complete gear strength can be finished the certain input parameters are only provided.The finite element analysis of transmission gear contact and bending is an effective means of gear structural design and optimization. To establish the efficient and precise analysis of the gear contact and bending stress, there are some problems in the contact rigidity, mesh method, mesh density control, load lines. It is necessary to conduct in-depth study. There are so many gear pairs in transmission that it is difficult to analyze and calculate. At present, there is no application software having special module for gear stress simulation analysis. To develop professional modules of parametric modeling and simulation for gear stress analysis can greatly improve efficiency and shorten the design cycle.Main research contents in this paper are as follows:(1) Standardized summarization of the classical method of strength for involute gears.The contact and root stresses for the external involute gear are described in classical method. The allowable contact stress, allowable root stress and their amend coefficients are studied and analyzed in detail. The coefficients calculation process of standard is summarized, and standardization of gear strength calculation is achieved.(2) The finite element method research for involute gear stress.When establishing finite element model of the gear contact and bending, the right mesh method need to consider the accuracy and efficiency. Considering the key issues for the surface-surface contact analysis, APDL in ANSYS are used to complete the automated finite element modeling and simulation for helical gear contact stress based on three kinds of mesh methods. The optimal mesh approach has been found by analysis and comparison. The right mesh control and contact stiffness are obtained by exploring the effect of tooth surface mesh density and model stiffness for simulation result. The automated finite modeling and simulation of helical gear bending stress are completed with APDL. The effect of the mesh density on bending stress is studied in-depth by changing the cell size, local wire mesh refinement, local surface mesh refinement and so on, and, the right mesh control has founded. The effects of two different load locations are analyzed and compared.(3) Development of the modules for gear strength and gear stress finite element analysis.Based on the process of gear strength analysis and finite element modeling and simulation, the combination of APDL and UIDL in ANSYS is used to develop the gear strength analysis module and finite element modeling and simulation module in ANSYS interface. When the required parameters are inputted, the gear strength analysis module can complete analysis for the load factor, contact stress, root stress, allowable contact stress and allowable root stress. The gear contact finite element analysis module uses the mapped meshing method, and its mesh density and contact stiffness are both adjustable. The gear contact finite element analysis module uses the free-mesh method, its mesh density is adjustable, can also finish modeling and simulation with two loading method.(4) Analysis and evaluation of gears strength of a light truck transmission.The main parameters of transmission gears have been gotten by a light truck transmission analysis. The analysis of contact strength and bending strength for a transmission gears are completed using the development module. The finite element modeling and simulation of gears contact stress and bending stress are achieved. The finite element simulation results are compared and verified with the classical results. The safety factor and reliability factor for gear strength evaluation are analyzed and the gears contact strength and bending strength ate evaluated.