Dynamic simulation of a planetary gear set and estimation of fault growth on the sun gear

Planetary gears are widely used in aeronautic and industrial applications because of the properties of compactness and high torque-to-weight ratios. Due to high service load, harsh operating conditions or simply fatigue, faults may develop in gears. If the faults cannot be detected early, the health condition will continue to degrade, even the consequence of big economic loss or catastrophic accident. In this study, the vibration properties of a planetary gear set for different crack levels in the sun gear are investigated through dynamic simulation. A simplified crack growth model is proposed for the sun gear and the time-varying mesh stiffness of a planetary gear set with the crack on the sun gear is analytically derived using the potential energy method. Through analyzing the simulated vibration signals, a new method is proposed to estimate the crack growth without requiring the comparison with the vibration signals when the gear box is running in the perfect conditions.