Effects of the Geometry of Friction Interfaces on the Nonlinear Dynamics of Jointed Structure

Friction interfaces are commonly used in large-scale engineering systems for mechanical joints. They are known to significantly shift the resonance frequencies of the assembled structures due to softening effects and to reduce the vibration amplitude due to frictional energy dissipation between substructural components. It is also widely recognized that the geometrical characteristics of interface geometry have a significant impact on the nonlinear dynamical response of assembled systems. However, the full FE modeling approaches including these geometrical characteristics are extremely expensive. In this work, the influence of geometry of friction interfaces is investigated by using a multi-scale approach. It consists in integrating a semi-analytical contact solver into a high-fidelity nonlinear vibration solver. A highly efficient semi-analytical solver based on the boundary element method is used to obtain the pressure and gap distribution from the contact interface with different geometrical characteristics. The static pressure and gap distribution are then used as input for a nonlinear vibration solver to evaluate nonlinear vibrations of the whole assembled structure. The effectiveness of the methodology is shown on a realistic “Dogbone” test rig, which was designed to assess the effects of blade root geometries in a fan blade disk system. The friction joints with different interface profiles are then investigated. The obtained results show that the effects of the surface geometrical characteristics can have a significant impact on the damping and resonant frequency behavior of the whole assembly.