Planetary gear trains are widely applied in various transmission units.Whether strengths of all gears are accurately calculated or not can affect reliability of the entire system significantly.Strength calculation method for planetary gear trains usually follows the method for cylindrical gears,in which the worst meshing positions for both contact stress and bending stress cannot be determined precisely,and calculation results tend to be conservative.To overcome these shortcomings,a kinematics analysis for a planetary gear train is firstly performed,in which the influence of relative speed is investigated.Then the finite element strength analysis of a planetary gear train based on its transient meshing properties is carried out in ANSYS.Time–history curves of contact and bending stresses of sun gear,planetary gears and ring gear are respectively obtained.Also the accurate moment and its corresponding position of the maximum stress are precisely determined.Finally,calculation results of finite element method(FEM)and traditional method are compared in order to verify the effectiveness.Simulation and comparison show the stability of the proposed method in this paper.Researches in this paper establish the foundations for fatigue analysis and optimization for a planetary gear train.
