Influence of Contact States on the Dynamic Behavior of Rubbing Structures

Abstract

One of the most common failure modes for turbomachinery wheels is associated to high-cycle fatigue of blades. A classical way to extend the working life of those structures is obtained through the introduction of specific devices in order to reduce vibrational amplitudes during resonance. Different kinds of components are used such as shrouds and wires within power industry and under platform limiters for aeronautics. Dry friction between the devices and blades induces non linear behaviors and flattens the associated frequency response functions (FRF). Even if this phenomena is now well known, different interpretations are presented in bibliography to explain the origin of this flattening. The most common one is based on the dissipated energy while more recent studies propose a different approach and explain peak flattening by changes in boundary conditions induced by the stick/slip phenomenon. The objective of the proposed study is to progress towards a better understanding of the flattening phenomena during vibration of bladed assemblies in presence of dry friction. A simple case is analyzed in order to show the contribution of respectively energy dissipation and changes of contact state on peak levels.