In this paper two types of the dynamic reliability model are proposed and compared with the Weibull distribution of sliding wear. These models are concerned with the relationship between the hazard function and the dynamic reliability. One considers a differential equation form, called the DE model, the other takes an algebraic dependence, AE model. The physical problem used in the simulation deals with the sliding of multiple ring-disk system. The disk is carburized, and the ring is assumed to be much harder than the disk. The dynamic reliability and failure rate variation of the disk can be estimated by the critical wear depth during sliding. The results show that the predictions followed DE model and Weibull distribution are a little conservative. Some physical interpretations of the models are presented. Both models are recommended due to their acceptable RMS error, physical meaning and simple appearance. (C) 1997 Elsevier Science Limited.