| Summary: | 碩士 === 南台科技大學 === 高階主管企管碩士班 === 93 === In this study, two economic replacement models are presented for a two-unit system which is subject to failure rate interaction and ageing process. Failure rate interaction is described as follows. When unit 1 fails itself, it causes a certain amount of damage to unit 2 by increasing the failure rate of unit 2 of a certain degree, while each unit 2 failure makes unit 1 failure, i.e. each unit 2 failure make the system total failure. Without failure rate interaction between units, the failure rates of two units also increase with age by ageing process. All unit 1 failures are assumed to be corrected by minimal repair.
In the Periodical Replacement model: The two-unit system is replaced by a new one at age T or on total failure, whichever occurs first.
In the Dicrete Replacement model: The two-unit system is replaced by a new one at the instant of the n-th unit 1 failure or on total failure of the system, whichever occurs first.
Introducing relative costs, the long-run expected costs per unit time are derived as a criterion of optimality in two models. The optimal replacement period and the optimal number will be found by minimizing that costs. And, the optimal and are also verified finite and unique under certain conditions. Numerical examples are given to illustrate the models
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