ABSTRACT
All industrial systemsaresubject toaging.Althoughthe actual effect of wear-out depends on the specific equipment considered, it might be stated that aging entails soon or later a decrease in the global performances of the system. Most of the time, maintenance models do tackle the issue of failure probability increase due to aging. It should however be recalled that on the one hand failure rates are not always strictly increasing functions of time from the start of operation, and on the other hand, aging is also likely to affect, i.e. reduce, the productivity of the system (Marais & Saleh, 2008).
