| With the gear transmission towards heavy-load, high-speed, low-noise,high-reliability, the modern design methods put higher demand on the static and dynamic characteristics and fatigue performance of gear transmission system. In this paper, the vehicle transmission gear is taken as the research object, modern calculation methods of gear strength are studied in detail, which provide more accurate and reliable theoretical guidances for strength calculation of gears. The main contents are as follows:(1) Mathematical model of involute, transition curve and helical gear with tooth profile deviation were established. In addition, based on 3D modeling and surface modeling of UG, parametric modeling methods of helical gear and error modeling methods of involute with tooth profile deviation were studied using parametric expressions and discrete data points of teeth profile.(2) Based on finite element analysis of bending deformation of cantilever, a testbed of finite element method verification for strength calculation of gears was designed.Further, the relation between solution precision, meshing methods, mesh density, and element types was studied. Besides, based on finite element method, statics analysis methods of helical gear pair were also studied using model of five pairs of gear teeth without rim and model of single gear tooth, in which course the tooth profile deviation’s effect on the static characteristics was also taken into account. The results show that, maximum tooth surface contact stress changes periodically, and the stress in double-toothed meshing zone is larger than that in three-toothed meshing zone,double-toothed meshing model should be used in fatigue life analysis method of helical gear pair. The calculation of gear root bending stress under static contact analysis or surface loads is of higher accuracy. Tooth profile deviation leads to a extension of toothsurface contact stress.(3) Analysis methods of dynamics of helical gear pair and influence of tooth profile deviation to the dynamic characteristics were studied using model of whole pairs of gear teeth and model of five pairs of gear teeth with rim based on finite element method and virtual prototype technology. The results show that, the dynamic mesh force obtained by flexible dynamics simulation analysis, changes periodically. Natural frequency range of different order were obtained through pre-stress modal analysis. At the same time, no resonate occurs in the gear transmission system, and the system possesses good dynamic properties. Dynamic characteristics of helical gear pair are fully reflected by transient dynamic analysis. Tooth profile deviation has significant effects on the driven gear’s angular velocity and the driven gear’s angular acceleration.(4) Fatigue life analysis method of helical gear pair and influence of tooth profile deviation on fatigue performance were studied based on load spectrum of flexible dynamics simulation model, stress-strain of helical gear pair under static load and the S-N curve of gear Materials. The results show that, minimum fatigue life helical gear pair appears on the contact line of driven gear and it is near to tooth top. The fatigue life of helical gear pair decrease with the increase of tooth profile deviation.(5) Finite element analysis modules of gear strength were developed using APDL and UIDL. The module functions contain material property definition, geometric model establishment, meshing, static contact analysis, modal analysis and so on, making modular and automatic analysis of finite element method for gear strength calculation realized. |
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