Entropy is an extensive property. If we isolate an area enclosing the system and its environment such that no heat, mass flows, or work flows in or out, then we can keep tabs on the total entropy (Figure 2.1).
In this case the entropy generated from the isolated area has
the total entropy of a system is equal to the sum of the entropies of the subsystems (or parts), so the entropy change is
We now can define here the Cumulative Entropy Damage Equation:
where, for the ith subsystem (see Equation (1.9)),
This seemingly obvious outcome (Equation (2.2)) is an important result not only for complex system reliability, but also for device reliability. This will be detailed throughout this chapter. ...