A micro-slip friction modeling approach and its application in underplatform damper kinematics

Underplatform dampers are widely used to dissipate vibration energy and to further prevent high cycle fatigue in turbine blade systems. The purpose of this work is to improve the simulation of the frictional contact of blade platforms/dampers in the modeling of a blade-damper system. A micro-slip friction modeling approach was developed by combining the classic Iwan model with a known contact pressure distribution on the contact surface. The proposed model creates a relationship between the contact pressure distribution and the density function used to describe the tangential force-displacement relationship in the Iwan model. In contrast to the classic Iwan model, the proposed model does not introduce any additional parameter related to the density function of the tangential force. Experimental results from a laboratory asymmetrical underplatform damper test rig were employed to validate our model. A dedicated contact parameter extraction procedure was devised, based on a random sampling method, to obtain the friction coefficient and contact stiffness. The effect of the contact pressure distribution on the prediction performance of the proposed model was further studied by comparing three distributions of contact pressure. The out-of-phase movement was analyzed numerically, and results show that the proposed model provides an accurate prediction of the behavior of nonlinear damper mechanics.