Nonlinear characteristics of gear pair considering fractal surface dynamic contact as internal excitation

A novel gear fractal backlash model is established to better consider joint action of all microscopic asperities on gear dynamics, which has the dynamic form from gear center motion simultaneously in this paper. Based on the fractal surface dynamic contact as internal excitation, a gear dynamic model involving surface morphology and gear center motion is established, and a corresponding close-loop algorithm is proposed to solve system dynamics by combining mesh stiffness and time-varying pressure angle. Accordingly, the chaos of the gear system is analyzed by the bifurcation diagram, phase portraits, and Poincare mapping. The comprehensive and strong influence of dynamic fractal backlash on the nonlinear characteristics of the gear system is also demonstrated. The intense effects of tooth surface topography through fractal backlash are explained in detail. Comparison with experimental data is conducted to verify the superiority of the proposed model.