In this paper, the problem of spalled bearing vibration signal modelling is addressed. Based upon results mainly obtained by a Time-Frequency Analysis of experimental signals, classical approaches are discussed and their limitations are pointed out. Concerning the non-strict periodicity of the impulse train induced by the fault, a theoretical study of the so-called quasi-periodic impulse train is performed. The main consequence of this phenomenon lies in the reduction of the frequency range relevant for diagnosis. Concerning the effect of the load distribution, we propose two approaches which can account for the observed frequency variations. The first one is to define a Time-Frequency Characteristic of the load distribution. But, despite its simplicity, this approach does not provide a complete description of the phenomenon. The second approach, consisting in modelling the bearing by a linear time-varying {mass, spring, damper} system, appears to be very well-suited to account for the observed phenomenon. (C) 2000 Academic Press.
