MTBF specification in a multiple use environment

A criterion, in the form of an equivalent failure rate equation, is developed which allows for the mean time between failures (MTBF) specification of a configuration item that is used in different environments and subject to a varying amount of operational stress. The degree of stress is formulated as a function of the output state, time spent in that state, and a corresponding duty cycle. A methodology is formulated which allows for the expression of failure rates that are associated with multiple conditions resulting from a complex operational scenario. The failure rate equations resulting from this scenario are used to generate a specification that is tailored for a multiple-use environment