The film forces in journal bearings may cause self-exciting oscillations under particular operating conditions; if the amplitude of these oil-whirl oscillations becomes too large, it may involve unsafe machinery dynamics. Thus, there is a need to understand the dynamic characteristics of the journal bearings evaluating the performances of the couple stress lubricants used to minimise the friction losses in steady operating conditions. The purpose of this paper was to illustrate a method to formulate with closed-form solutions the non-steady fluid film forces, and the stiffness and damping coefficients for ‘short’ liquid-lubricated couple stress journal bearings, assuming the micro-continuum Stokes’ model. It is shown that the model allows the advantage of minimising the computational time required for the nonlinear dynamic analysis of couple stress journal bearings without any significant loss of accuracy, while the analytical form of the solution involves a better readability of the parameter effects on the system unsteady behaviour.
APPROXIMATE CLOSED-FORM SOLUTION FOR THE DYNAMICAL ANALYSIS OF SHORT BEARINGS WITH COUPLE STRESS FLUID
SENATORE, ADOLFO;RUGGIERO, Alessandro
2007-01-01
Abstract
The film forces in journal bearings may cause self-exciting oscillations under particular operating conditions; if the amplitude of these oil-whirl oscillations becomes too large, it may involve unsafe machinery dynamics. Thus, there is a need to understand the dynamic characteristics of the journal bearings evaluating the performances of the couple stress lubricants used to minimise the friction losses in steady operating conditions. The purpose of this paper was to illustrate a method to formulate with closed-form solutions the non-steady fluid film forces, and the stiffness and damping coefficients for ‘short’ liquid-lubricated couple stress journal bearings, assuming the micro-continuum Stokes’ model. It is shown that the model allows the advantage of minimising the computational time required for the nonlinear dynamic analysis of couple stress journal bearings without any significant loss of accuracy, while the analytical form of the solution involves a better readability of the parameter effects on the system unsteady behaviour.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
