ABSTRACT
The earliest model of system behavior for the case in which repair does not imply renewal was suggested by R. E. Barlow and L. C. Hunter. Their model is called the "minimal repair" model as it is constructed by assuming that when failure of a device occurs, the unit is repaired and is placed back in operation without any change in its age. The minimal repair models were the first to capture the feature of real operating equipment that often is not renewed by repair. The key to the analysis of this basic imperfect repair model is the fact that the times at which a perfect repair is performed constitute a renewal process that is embedded in the more general point process produced by the device failures. In an attempt to make the nonstationary models more realistic, M. Brown and F. Proschan defined "imperfect repair."
