Contact interface damping effect on internal friction and rotordynamic instability

Abstract

Rotating machinery shafting is typically comprised of multiple components that are assembled to ensure reliable operation, proper alignment minimal vibration. However, conventional rotordynamics approximates the shafting as a single, continuous member, neglecting contact interfaces between the components. The presence of an interface can induce microslip, which generates internal friction that may cause instability and machinery failure. A novel approach of modeling the interface viscous damping effect on rotordynamics is proposed by combining a GW (Greenwood and Williamson) contact model with the Yoshimura damping model. All structural components are modeled using 3D solid finite elements. Modal damping ratio is utilized to identify the instability onset speed (IOS). The results show that internal friction has a destabilizing effect on whirl motion above the first critical speed, but has a stabilizing effect on the motion below the first critical speed. The destabilizing effect can be reduced by increasing the bearing damping, however excessive bearing damping can drive the effective damping towards negative values. Increasing the number of interfaces reduces stability while increasing an interface preload prevents microslip, and increases stability. Lastly, smoother surfaces at the interfaces increase the IOS.