Dynamic behaviour modelling of a flexible gear system by the elastic foundation theory in presence of defects

In this paper a novel approach for modelling a spur gear system using finite element method combined with elastic foundation theory is developed. The pinion is modelled by shaft finite element and the wheel by a three-dimensional finite element. Elastic foundation is utilized to model the gearmesh. The modal analysis showed the presence of lower natural frequency for thin rimmed gear cases susceptible to be excited by the operating running condition. The transmission error is affected by the wheel shape and by the presence of lower natural frequencies. Eccentricity error and tooth crack are also modelled to observe their influence on the dynamics behaviour of the system. It was found that they are responsible of the apparition of an amplitude modulation.