Abstract
The stiffness and dampness parameters of journal bearings are required in rectangular coordinates for analyzing the stability boundary and threshold speed of oil film bearings. On solving the Reynolds equation, the oil film force is always obtained in polar coordinates; thus, the stiffness and dampness parameters can be easily obtained in polar coordinates. Therefore, the transformation between the polar and rectangular coordinates of journal bearing stiffness and dampness parameters is discussed in this study.
Highlights
Due to the oil whip effect in a rotating hydrodynamic journal bearing, self-excited vibration occurs in the oil film, which increases with an increase in the rotation speed [1–4]
As a result of the self-excited vibration, threshold speed and stability boundary exist for the rotating bearings
Jang and Kim [11] studied the dynamic characteristics of journal bearings with five degrees of freedom (DOF) and derived the perturbation equations
Summary
In modern industry, rotating parts of engineering equipment are supported by journal bearings in the vertical direction. The Reynolds equation is derived with respect to Cartesian coordinates and stiffness and damping coefficients are obtained by integrating the new equations Based on this method, Jang and Kim [11] studied the dynamic characteristics of journal bearings with five degrees of freedom (DOF) and derived the perturbation equations. The coordinate system applied in the previous study on linear threshold speed and stability boundary was either polar coordinates or rectangular coordinates for the complete calculation, which complicated the analysis To address this complication, the transformation between polar and rectangular coordinates of journal bearing stiffness and dampness parameters is discussed in this study. The stiffness and dampness parameters in rectangular coordinates can be applied to calculate linear threshold speed and stability boundary of hydrodynamic bearings
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