Estimation of critical speeds of a rotor supported on ball bearings

In this work study of a rotor supported on ball bearings and containing a fatigue crack is carried out. The primary objective of the work is to obtain the load-distribution of the ball bearings from which the support stiffness in two transverse directions are obtained. The other objective is the rotor-dynamic analysis of a shaftsupported on these bearings. A mathematical model of a rigid rotorsupported on flexible bearings is considered for the purpose. Effects of bearing stiffness, damping and gyroscopic effects are included in the study. The governing equations of motion are obtained. The whirl frequencies of the rotor system are obtainedusing Eigen value formulation of the problem. A Campbell diagram is plotted which is used to obtain the critical speeds of the rotor system. These results are supported with the results from frequency response function plots.