A state-dependent wear model with an application to marine engine cylinder liners

In this paper a new wear model is proposed in which the transition probabilities between process states, unlike models with independent increments, depend on the current system state. The model is used to describe the wear process of the cylinder liners of some identical heavy-duty diesel engines for marine propulsion. The application is developed on the basis of a real dataset of wear measures obtained via staggered inspections. A time and state space discretization is introduced to obtain the likelihood function of the observed data. The model parameters and reliability characteristics of the liners are then estimated and the wear growth during future inspection intervals is predicted. The homogeneity of wear data and the goodness of fit of the proposed model are tested. A simplified maintenance scenario is also considered to show the need for accurate modeling of the wear process for planning condition-based maintenance activities. Finally, inferential, predictive, and decision-making results derived within the proposed model are compared to those obtained within one of the most widely used age-dependent wear models. Fortran codes and executable programs, as well as the cylinder liner data, are available online as supplemental material.