Abstract: An experimental and theoretical investigation on the transient dynamic performances of a flexible rotor-SFDB system during passage through resonance is presented. The relationship among the boundary condition of oil-film pressure, unbalance load, speed range and jump phenomenon is discussed and a parameter of critical unbalance load for jump phenomenon,ucr, is introduced. The parameter ucr should be considered as the limit value of unbalance load of the rotor system in engineering designs.

Key words: squeezed oil-film damper, through resonance, jump phenomenon.