IMPROVED MATHEMATICAL MODELS AND DYNAMIC ANALYSIS OF LIGHT ROTOR-BEARING SYSTEMS UNDER UNBALANCE AND STOCHASTIC EXCITATION WITH APPLICATION TO A GRINDING MACHINE.

摘要

Detailed stability analysis and accurate evaluation of the response of the light rotor-bearing systems are presented using improved mathematical models for both the rigid and the flexible states of the rotor. The nonlinear stiffness and damping of the finite bearing are specified through a numerical approach maintaining a practical treatment for the cavitation boundaries and leading to decoupled equations of motion from the hydrodynamic pressure equation. Using both linear and nonlinear approaches, modified stability boundaries are defined and further details about the nonlinear behaviour are obtained.;The equations of motion for the general case of flexible rotor-bearing are assembled using the finite element method and taking into account the gyroscopic moments, the rotary inertia, the shear deformation, the internal damping and the bearing support flexibility preserving the dimensions of the constructed system to a minimum. General modal analysis is applied on the nonsymmetric dynamical systems for the evaluation of both the deterministic and stochastic responses. Error bounds for justification of the linearized rotor-bearing system are provided in a chart form and comparisons with previous studies are made. An application of the rotor-bearing results on a grinding machine spindle wheel system is carried out with a new emphasis on the definition of rotor rigidity.