Volume 100 (1996)




1996, Zeszyt 100

Nonlinear model of vibrations in rotor-bearings system. Part I. Calculation algorithm


The paper presents a theoretical model affording for non-linear description of the oil vibrations occuring in the rotor -bearings-supports systems after exceeding the stability threshold. A new approach to the determination of  the elasto-damping properties of the oil film, not based on the commonly used principle of superposition of pressure or the hydrodynamic forces in the bearing, is put forward. The dynamic features of the oil film are determined by the coefficients of stiffness and damping, non-linearly variable in time, calculated by using a fast and modefied pertubation maethod. The method applied to describe the oil film properties makes it possible to take advantageof the equations of motion, relating to the entire system, derived on the finite elements method.

The theoretical model takes also into account the effect of heat exchange within the bearing. With regard to kinetostatics problems the temperature distribution in the film is calculated on the basis of a complicated, so-called diathermic model of the bearing. On this basis it is possible to determine the mean "effective" dynamic viscosity of ,the oil, futher applied to the problem" of the system dynamics. 

There has been presented a general calculation algorithm  computer prograrn- consisting of two parts clearly separated from each other, the kinetostatic one and the dynamic one. 

The paper also gives examples of experimental verification of the model at a special large-size test ring. The experimental tests and the verificatign were carried out in the sphere of small oil vibrations. 


rotor -bearings-supports systems, non-linearly variable, oil vibrations