A quasi renewal process and its applications in imperfect maintenance

This paper proposes a quasi renewal process, and its application in maintenance theory is discussed. The properties of this quasi renewal process are studied and its renewal function is derived. Three imperfect maintenance models are proposed and they model imperfect maintenance in a way that, after maintenance, the lifetime of a unit will decrease to a fraction of its immediate previous one. According to the theory of the quasi-renewal process developed in this paper, the expected maintenance cost rate and availability are obtained and optimum maintenance policies are discussed for these three models. Finally, a class of related optimization problems is discussed and a numerical example is presented