Stress Distribution And Life Characteristics Analysis Of Flexspline In Harmonic Drive

With the development of aerospace in our country, more and more harmonicdrives have been used, and currently60%of the reduction gear is harmonic reducerin the field of aerospace. As an elastic part with thin wall in harmonic reducer,flexspline’s fatigue life severely limits the service life of harmonic reducer.Studying the fatigue life problems of harmonic reducer is a practical and significantengineering work. In this paper, the study on structure parameters and positioneffecting on stress and fatigue life of flexspline using finite element method hasbeen carried out.Take XB1-60type of harmonic reducer as an example, the key structureparameters of three parts in harmonic reducer are calculated according to theempirical formulas. And the parameterized3D model is established by using Pro/Esoftware. Based on the analysis of the actual working process of harmonic reducer,the assembly model of flexspline and wave generator are built by considering theinfluence of the tooth and ignoring the influence of the convex sets at the bottom offlexspline and the wave generator bearing stiffness. The3D model is imported intoANSYS through the interface of Pro/E and ANSYS, and the finite element model ofharmonic reducer is established. The stress of the flexspline is analyzed based oncontact analysis method by setting the boundary conditions and constrains. And thevalidity of the model is proved by comparing with theoretical calculation results.The stress distribution of the flexspline is obtained by using contact analysismethod on different variation of key structures, including cylinder length, thickness,tooth width, fillet radius and cutting edge length. The Von Mises stress of differentsections and parts and the corresponding curves using the polynomial fitting methodare obtained. The effects of variation key structural parameters on flexspline and themaximum equivalent Von Mises stress is analyzed, and the dangerous section offlexspline is found. These results will be useful for size parameter optimization offlexspline. Besides, the flexspline and wave generator contact stress under differentpositional accuracy conditions is obtained, and the variation law of the stress indifferent section and parts of flexspline are analyzed.On the basis of stress analysis of flexspline that has been done previously, thefatigue life under different stress condition of flexspline by using the S-N curemethod is estimated. Using polynomial fitting method, the curve of the relationshipbetween stress and fatigue life is obtained. Finally the variation law between fatiguelife and variation structure parameters and the relative position and coaxiality areanalyzed, which provides the basis for structure parameters optimization of flexspline.