Determination of Optimal Replacement Period for A Multicomponent System Consider with Failure Types

고장형태(故障形態)를 고려(考慮)한 다부품장비(多部品裝備)의 최적교환시기(最適交換時期) 결정(決定)

In this paper, it is assumed that a system is composed of an essential unit and a nonessential unit. During the running of the system, an essential unit is replaced at periodic replacement time T or at nth failure of essential unit whichever occurs first. Nonessential unit is replaced at its failure and at the replacement of essential unit. This paper derive optimal replacement period which minmises the total expected cost for replacement. The unimodality of totoal maintenance cost function is proved under the assumption that hazard rate of each component is continuous and monotone increasing failure rate(IFR). Based on this condition, it is shown that the optimal replacement period is finite and unique.