Modified, Discrete Replacement Models

This paper proposes four modified replacement policies where a unit may be replaced only at periodic times nT (n = 1, 2, ...) for a fixed T > 0. Age, block, periodic, and inspection models can be transformed to discrete replacement ones. The mean cost-rates of each model are obtained and the optimal numbers to minimize the cost-rates are discussed when the hazard rate is monotonely increasing. Derivations are given in a separately available Supplement.