Basic Concepts of Reliability Analysis

Abstract

This chapter introduces the basic concepts associated with reliability analysis, taking as an example the investigation of non-repairable systems. An important part of such an investigation deals with failure rate and failure mode analyses. The failure mode analysis will be discussed in section 2.5. The failure rate analysis leads to the predicted reliability, i.e. to that reliability estimate obtained analytically from the reliability structure of the system and the failure rate of its elements. The prediction is useful to detect reliability weaknesses, to quantify the utility of reliability improvements (derating, screening, redundancy) and to compare alternative solutions. It is performed according to the following procedure:

• 1. Definition of the system and of its associated mission profile; derivation of the corresponding reliability block diagram.

• 2. Determination of the stresses applied and of the corresponding failure rate (λ) for each element of the reliability block diagram.

• 3. Evaluation of the system reliability function (R_S(t)).

• 4. Elimination of reliability weaknesses and return to step i or 2, as long as necessary.