| Summary: | 碩士 === 中華大學 === 機械工程學系碩士班 === 96 === This thesis investigates dynamic characteristics of spur and helical planetary gear systems using continuously geometric models of the finite element approach (FEM). Not through a CAD geometric process but directly using the derived involute tooth profile equations generated by a rack cutter, high quality element models of planetary gear systems are parametrically and automatically constructed. After assigning suitable analysis conditions, numerical modal and dynamic responses of the planetary gear systems are solved by the commercialized general purpose dynamic FEM software, LS-DYNA, through which system natural frequencies, modal shapes, and dynamic fillet stresses are calculated. Additionally, the harmonic resonance of fillet stresses arising from excitation of nonlinear meshing stiffness of tooth pairs is also discussed. Accordingly, the connection between system modal characteristics and dynamic fillet stresses can be found. Finally, sophisticate parametric studies are performed in order to reveal the effects of variant influential factors on the modal and dynamic characteristics of planetary gear systems. Effect of material properties and design factors on modal behaviors and dynamic responses are incorporated. In the aspect of modal analyses, influences of Young's modulus (stiffness) and density (inertia), carrier stiffness, supporting bearing stiffness, gear module, helical angle, distributing angles of planet gears, number and meshing position of engaging tooth pairs on the modal characteristics are investigated. Plentiful useful results of gear modal property are obtained through the study. In the dynamic aspect, influences of the ring gear addendum and backlash of meshing gears on the dynamic fillet stresses of planetary gear systems are also discussed. Potentially, the proposed continuum geometry FEM approach can be served in analyzing dynamic problems of wide categories of planetary gear systems. The obtained modal and dynamic results are quite referable in design of planetary gear systems.
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