Abstract:The time-varying meshing stiffness (TVMS) provides important information about the health status of the gear system. Tooth faults, like crack, pitting, spalling and breakage will change the TVMS. In order to comprehensively understand the vibration properties of a helical gear set, it is necessary to evaluate the mesh stiffness effectively. In this paper, slicing method, discrete integral method and potential energy method are combined to analytically evaluate the mesh stiffness of a helical gear set. A crack model is developed and the mesh stiffness reduction is quantified when a crack occurs in the pinion or the gear.