2. Practical Applications of Bearing Dynamic Coefficients

Regardless of the type of bearings, be it rolling-element, gas, magnetic, or hydrodynamic, we assume that the dynamic coefficients of bearings determine the rotordynamics (in addition to other factors such as the rotor design, the material it is made of, the properties of the supporting structure, etc.). Their values result directly from the properties of the bearing. Due to the nature of operation of different types of bearings, they are characterized by stiffness and damping coefficients falling within different ranges. The conditions in an oil-based hydrodynamic bearing and in a rolling-element bearing are sufficiently different to result in different dynamic coefficient values. Higher damping value can usually be found in hydrodynamic bearings, while higher stiffness coefficient values are typical in rolling-element bearings. At this point it should also be stressed that the dynamic coefficients of bearings should be treated as an “abstract creation” of sorts, which is often impossible or very difficult to measure directly. It is also often connected with large error. With correctly determined values of stiffness and damping coefficients of bearings, the created numerical models reflect the results of experimental research very accurately. The creation of such models enables the design of a properly functioning rotor–bearing–supporting structure system.