LAUSR

Manufacturers and consumers prefer reliable products, or systems in general, since they need to assure that systems work satisfactory for given mission times. The redundancy allocation to original system components is a common technique to improve reliabilities. But, allocation of redundants is not an easy task and must be considered properly with respect to environmental working conditions and possible restrictions such as cost, volume and weight. Therefore, the problem of finding optimal allocations is important and studied extensively in literature. The existing studies usually assume restrictive conditions such as stochastically independent component and spare lifetimes. This article deals with this problem under a general setting in which component and spare lifetimes can be dependent and heterogeneous. Two common policies, called active and standby, are studied in details. Stochastic orders are implemented for comparing various allocation policies. Findings of this article are derived under general conditions and hold for arbitrary dependency structures among lifetimes. Illustrative examples are also given.