Effect of mesh stiffness of healthy and cracked gear tooth on modal and frequency response characteristics of geared rotor system

Geared rotor systems are used in industrial machinery, automotive applications etc. to provide rotational speed changes and torque variations by transmitting rotational motion from driving shaft to the driven shaft. Gear tooth contact, as modelled using gear mesh stiffness and damping, considerably affects the dynamic characteristics of the system. This work primarily studies the effect of mesh stiffness and damping due to gear pair on the modal characteristics of the geared flexible rotor-shaft system supported on compliant bearing. The rotor-shaft is modelled using Timoshenko beam elements; whereas non-proportional viscous damping model is used to represent bearing and gear mesh damping. Fatigue loading causes development of gear tooth crack, which results in reduction of mesh stiffness. The effect of various cases of cracked gear tooth has also been investigated on the modal characteristics and frequency response functions of the system. The changes in the modal and frequency response characteristics due to cracked gear tooth have been compared with that of healthy geared rotor system. The study may prove helpful in detection of faults developing in the gear tooth by observing the changes in the dynamic characteristics of the system.