Rotor-Ball Bearings System Under Variable Regime

One of the most frequent events that can occur in rotating machinery is bearing damage. Diagnosis of bearing failure under varying operating conditions present a huge challenge for research and investigation. In this paper, a model based study of a rotor-bearing system is carried out under variable speed and load conditions. The model studied refers to a real test bench developed at the ITHIMM laboratory of the University of Reims in France. It consists of a line of rotating shafts supported by two identical ball bearings, excited by a synchronous electric motor, and radially preloaded by a hydronic actuator. Based on the Hertizian contact theory, the proposed model has been performed in the case of a crack defect in the outer ring of the load-side bearing. The equations of motion of the system are formulated and solved using Newton Raphson combined with Newmark algorithms. Because of the noise masking effect, the recorded time response signal does not clearly show the defect impulses. Therefore, wavelet de-noising techniques are used to highlight the damage. A designed time-frequency envelope spectrum is also applied to the noise-free signal to study the effect of the speed and load variation on the defect frequency.