Experimental and numerical analysis of the dynamic behaviour of a foil bearing structure affected by metal shims

This paper gives a detailed overview of a shimmed first generation gas foil bearing (GFB). Three metal shims are inserted inside the elastic GFB structure between the bumps and the bearing sleeve. Dynamic shaker tests with a harmonic excitation are used for evaluating dynamic stiffness and damping of the elastic structure. In addition, a numerical structural bump model, based on a link-spring model, is applied to confirm the experimental results, where a dynamic friction model with pure Coulomb friction is used. It neglects Stribeck's effects and avoids numerical problems in time domain analysis. Good agreement between experiments and simulations is observed.