Abstract
In order to apply failure diagnosis of a rotating machine, normal and abnormal vibrations of a rotating-element bearing were formulated by Herzian contact theory and the results of numerical simulation were applied to decide the existence of a defect. In this paper, firstly three dimensional dynamics of a rotating-element bearing under thrust load were considered and motion equations of bearing elements were developed. And then, in order to consider abnormal vibrations by bearing defects, defects were classified to the three types of impulse train and these impulse trains were added to the motion equations. Moreover, some numerical simulations were conducted by Runge-Kutta method and compared with experimental examples. In the result, it was found that thrust vibrations of a rotating-element bearing has one eigen frequency and this eigen frequency does not change largely by rotating speed and presence of a defect. Using these characteristics, the new method of failure detection was applied to a rotating-element bearing at low speed and the effectiveness of this diagnosis method was confirmed by an example.
