A HYBRID MODEL FOR WEEKDAY REPLACEMENTS WITH INFANT-MORTALITY FAILURES

A hybrid availability model of a repairable system with infant mortali ty failures is proposed. The hybrid model can efficiently represent di fferent types of state transitions by the use of a hierarchy of models : (1) a time-discretized component submodel, which provides a piecewis e-linear failure rate during an operating interval; (2) a phased-missi on model, which transforms the state probability vector according to r epair activity; and (3) a combinatorial model, which is used to predic t the number of working units among a collection of identical componen ts. The modeling approach is illustrated by predicting the expected nu mber of working components for a multiple-component system where repla cement components are ordered at the end of business hours each weekda y end. Replacement occurs on the next weekday morning. (C) 1998 Elsevi er Science Ltd. All rights reserved.