MEASUREMENT OF OIL FILM JOURNAL BEARING DAMPING COEFFICIENTS - AN EXTENSION OF THE SELECTED ORBIT TECHNIQUE

This paper describes a novel experimental procedure for measuring the four velocity or damping coefficients of an Oil Film Journal Bearing f rom imposed dynamic orbits. All four damping coefficients are derived from one imposed journal center dynamic orbit and, therefore, may be r egarded as being obtained at the same time. The method requires the pr oduction of a ''figure of eight'' shaped orbit and utilizes the ''cros s-over'' point therein. Coefficients are initially evaluated in a coor dinate system which is chosen to align with the designated parts of th e measured orbit. Each coefficient is then separately evaluated from s ingle values of instantaneous imposed force and resulting journal cent er velocity. Coefficients are then converted into any other desired ax es system. All the benefits of the original selected orbit technique a re retained. The presented method places much less severe demands on e xperimental procedure. An available example illustrates the technique. A realistic uncertainty analysis for this example is included. Indica tions are provided which show how the orbit features may be adjusted t o substantially reduce uncertainty.