Static Normal Stress Influence in Friction Damping of Blade Attachments

Abstract

It is well known that friction is really important to reduce amplitudes of vibration of rotor blades. Several approaches based on the classical Coulomb friction law have been used in order to model the friction damping at those interfaces, but their results are not accurate enough for those cases with small displacements and high normal loads. A more accurate method has been developed (InTerPart MIcroslip COntact method in [1]) to represent the damping introduced by these kind of friction sources. An improvement of this method has been made taking into account a more-in-depth study of the influence of normal stresses in those contacts areas under high normal stresses and small displacements (using the blade attachment friction source as reference). The paper includes a detailed study of the sensitiveness of different blade attachments to different normal stress distribution along the contact face, and the influence of this distribution in damping results. Experimental results are also presented to make comparison with simulation ones. These experimental results have been obtained from the test rig used in case 3 ([1]), but using different attachment geometries under the same conditions.