Subcritical behaviour of short cylindrical journal bearings under periodic excitation

Abstract Rotating machinery supported on journal bearings is affected by forces due to rotating unbalance and pressure gradients in the oil film. The interaction of these can evoke nonlinear behaviour, including asynchronous motion even chaos. This work attempts characterise sub-synchronous rigid rotor cylindrical abovementioned interaction. analysis focuses behaviour at speeds lower than threshold speed for whirl, associated with vibration magnitude equaling bearing clearance. It shown that occur well before reaching underlying period-doubling bifurcation depends amount unbalance. response stability are analysed using a numerical continuation method employing infinitely short model. Continuation results further validated time simulations which utilise finite difference compute hydrodynamic forces. validation process employs diagrams, Poincaré sections estimates largest Lyapunov exponents.