Abstract: In this work, the dynamic behaviour of misaligned rotor is presented. The rotor is mounted in two hydrodynamic journal bearings and has two degrees of freedom. Reynolds’ equation is obtained by considering the effect of mass transfer across the fluid film. This is discretized by means of the finite difference method and solved numerically. By integrating the oil pressure distribution, the hydrodynamic forces are calculated. The elasticity of the fluid film is modelled by stiffness and damping matrices. The motion equations have been established for the rotor bearings system and simulated with Newmark method. The effect of bearings geometry on the dynamic coefficients is presented. A theoretical model describing the angular misalignment defect is analysed in order to survey the vibratory response of the misaligned rotor. Numerical simulation results are presented and discussed.

Abstract: Gearbox power transmissions are widely used in the automotive industry. They have a complex vibro-acoustic behaviour that is influenced by the various acoustic–structural interaction mechanisms. This paper concentrates on modelling these systems using a three-dimensional finite-element (FE) approach for the structure combined with a Rayleigh integral (RI) method for the acoustic radiation process. A modal analysis method is used to evaluate the elasto-acoustic modal characteristics for the coupled system. Effect of the fluid inside the gearbox on the vibration response is discussed. The combined use of this FE/RI model enables evaluation of the acoustic response. A case study of a simplified gearbox internally excited with gear mesh stiffness fluctuation is presented. Vibratory analysis allows concluding that the vibro-acoustic coupling between elastic housing, air-cavity and free acoustic field have not to be neglected.