Experimental studies (out of operation):
The foil bearing consists primarily of compliant foil structures connected in series with the lubrication film to provide stiffness and damping. This additional viscoelastic property keeps the bearing more robust to harmonic and subharmonic shocks and protects the minimum lubrication film thickness from failure.
Based on this consideration, the dynamic properties of the foil structure as a function of the excitation frequency play an essential role. In this respect, SADAP offers a careful investigation of the dynamic behavior of the foil bearings with a focus on film structure and out of service. This type of investigation is called measurement of the mechanical impedance of the foil structure.
The bearing assumed for investigation is harmonically excited in two directions perpendicular to each other (up to 9000 Hz) and the deflection in the respective directions is measured. Post-processing of the measured data determines how the stiffness and damping coefficients of the foil structure react to different frequencies that may occur during operation.