ABSTRACT
Maintenance models and their optimum solutions have been studied extensively in literatures; however, it would be of interest to investigate the reliability properties of the extended failure rates in these models. This paper surveys the failure rate functions of replacement times appeared in the recent age, random, and periodic replacement models. Their properties are obtained in inequality forms and examples are given to show how they are found in the models of replacement first, replacement last, and replacement overtime. The survey in this paper is conducted when the analytical replacement times are obtained so that it would be helpful to understand the complex maintenance models theoretically.
