Effect of straightness tolerance on unbalanced response of flexible shaft passing through critical speed

Abstract Since the more destruction in rotating machinery occurs during start up or run down, the main purpose of this study is to investigate the influences of shaft bow coupling with unbalance fault on the rotor response for passing through critical speeds. The Finite element model is developed for a more realistic analysis. The Newmark-β method to solve the nonlinear lateral vibration of rotor-bearing systems is approached and the effects of various parameters including shaft bow, unbalanced mass and support parameters are shown. The results illustrate the crucial role of shaft bow when it is coupled with unbalance fault in phase of each other for passing through critical speed. As a result, in order to bring a rotor up to speed over the critical one, the source of energy can only grow the amplitude of vibration instead of angular velocity.