3 REPLACEMENT MODELS WITH 2 KINDS OF DAMAGE

This paper proposes three replacement policies for a modified cumulati ve damage model. An item receives shocks and suffers two kinds of dama ge: one is produced by shocks and the other increases with time at con stant rate a. It fails only when the total damage exceeds a failure le vel K at some shock and is replaced before failure at time T, at shock N, or at damage k. The expected cost rates of three replacement polic ies are obtained. When shocks occur in a Poisson process, optimal T, N and k* which minimize them are computed numerically. Finally, two e xtended cases where a is a function of time and K is a random variable are also considered. (C) 1997 Published by Elsevier Science Ltd.