Gearbox is commonly regarded as the most important power section of wind turbines which has been widely valued for its high malfunction rate. Gear fault researches mainly include wearing, pitting, spalling, breakage, falling off, etc, while little attention was paid to tooth Flank Pitch Error(FPE). Taking a single-stage parallel shaft spur gear as the research object, an 8-DOF gear transmission model and the FPE model were established in this paper and the gear’s time-varying meshing stiffness (TVMS) models with & without tooth FPE were obtained respectively, which the dynamic models with various tooth FPE values under different rotating speeds were simulated after. The simulation results showed that the TVMS mathematical model proposed in the paper under tooth FPE is practical at both low and high rotating speeds. Under the FPE model, side-bands are formed around each multiple of meshing frequency whose peaks are distributed by a fixed fault characteristic frequency ffp interval. The gearbox vibrates severely as the tooth FPE values and rotational speed grow. The peak value of the vibration signal is about 3 times that in case of fault-free state when the FPE value reaches 0.001rad, thus the impact of FPE on gearboxes cannot be neglected.

Tooth surface wear is one of the most common faults of gearboxes which increases the fatigue load on the gearbox and endangers its stable output characteristics and service life. Gear meshing characteristics vary significantly with the wear location and severity. Thus, the wear fault model considering tooth profile deviation, friction and time varying mesh stiffness (TVMS) was established in order to quantitatively study the vibration characteristics of tooth fatigue wear (TFW). Tooth profile modification and friction coefficient coupling were applied to characterize TFW, and the maximum wear depth was introduced to characterize TFW severity. The gear-pair simulation models under multiple wear severities were established and imported to a single-stage parallel gearbox whose dynamic differential equation was established under multiple torque conditions. The dynamic simulation results showed good agreement with the experimental data, which validated the method’s effectiveness. The vibration characteristics under different wear severities and simulation conditions were then obtained and compared.