An experimental study on oil-film dynamic coefficients

The oil-film force of hydrodynamic bearing is often characterized by a set of linear stiffness and damping coefficients. This paper presents an experimental method to recognize these coefficients and establishes their characteristics under varieties of operating conditions. The fundamental test model is obtained from a Taylor series expansion of bearing reaction force. A delicate test rig is constructed and experimental data are acquired under various testing conditions. The coefficients are evaluated by means of least mean square in time domain. The experiments indicate that the linear oil-film dynamic coefficients are sensitive to the excitation force. The sensitivity is varied for the different coefficients. From the investigation, it can be seen that the linear model is invalid under condition of high excitation force. That is to say, the nonlinear components, which are ignored in traditional linear model, should be considered in those conditions.