Detection of localized damages in synchronous belts through monitoring the vibration of pulley's support.

The possibility of diagnosing the presence of localized damages in timing belts, by monitoring the vibration of the pulley’s support was analysed in this work. During the working life of a timing belt some types of damages can arise; they can involve localized losses of stiffness, and then discontinuity in the local strain. Tangential load variations can so excite the vibratory motion of the pulley. The simulations with an on purpose designed multi-body model of the synchronous transmission, confirm that vibrations arise on the pulley in presence of localized lack of stiffness in the belt. The oscillatory motion occur at the running frequency of the timing belt. Some experimental tests were performed on a proper test bench, measuring the vibrations of the support of the pulley, through piezoelectric accelerometer and signal analyzer. The vibratory signals was processed and analysed in the frequency domain, using the method of envelope and filtering the signals in a band around the meshing frequency. The spectra of the envelope regarding healthy and artificial damaged belts were compared. Preliminary results show an interesting increase of the peak amplitude at the belt run frequency, when a localized reduction of stiffness occur in the belt, thus confirming the effectiveness of the proposed diagnostic method.