Valutazione dell’effetto della dimensione del difetto nella risposta vibrazionale di un cuscinetto a rulli

In the latest years many researcher focused on the pollibility to foresee the failure of a mechanical system in the early stages in order to allow quick response times. Monitoring and diagnostics are at the base of those methodologies of predictive maintenance, which represents the standard for many big companies. All informations acquired by monitoring systems are sometimes not enough to make the next step, that is the possibility of diagnosing the cause of the failure. In the present work the possibility of a relationship between the response of a system and the dimension of a defect causing the vibration is explored. Through a non-Hertzian contact model a roller bearing is studied and a correlation is sought between the dimension of the defect and the frequency content of the contact pressure history. The use of a non-Hertzian approach enables the determination with good accuracy the overpressures due to edge e ects caused by the sudden change in curvature in presence of a defect. The estimation of the pressure variation can be used to estimate the amplitude of the harmonic content exciting the bearing during operation. Using consolidated signal analysis algorithms, in particular the envelope method, an in-depth analysis of the harmonic content of the signal to consider is possible. The possibility of building a correlation between the load and dimension of the defect which might help to identify the dimension of a damage from the estimated frequency content. It is then possible to identify the presence and nature of the defect, allowing an early diagnosis of the failure.