Influence of Tooth Surface Wear and Nonlinear Contact Stiffness on Dynamic Responses of Helical Gears

Background: Tooth surface wear is inevitable in helical geared transmission. Consequently, the worn profile deviates from the ideal involute one. As a result, the structural stiffness of worn tooth and contact stiffness of tooth-pair are both changed. Methods: This work presents an improved calculation method for structural stiffness of worn teeth by combining slicing and potential energy method, considering non-uniform distribution of wear amount along the tooth surface. Then, a nonlinear contact stiffness model is employed to investigate the influence of wear on contact stiffness. Meanwhile, taking wear as one kind of profile deviation, the analytical model of time-varying mesh stiffness (TVMS) of helical gear pair is derived. Furthermore, governing equations with 6 degree-of-freedom are established and influences of wear on dynamic responses are revealed. Results: Results indicate that structural stiffness of worn teeth decreases but contact stiffness does not always keep increasing or decreasing. The fluctuation of dynamic transmission error with the nonlinear contact model is not as significant as that from the constant contact stiffness model. Conclusion: The approach presented in this work is suitable for condition monitoring of helical gears in view of long-term service.