Can system reliability be predicted from average component reliabilities?

Abstract

The paper reveals that a prediction of system reliability on demand based on average reliabilities on demand of components is a fundamentally flawed approach. A physical interpretation of algebraic inequalities demonstrated that assuming average component reliabilities on demand entails an overestimation of the system reliability on demand for systems with components logically arranged in series and series-parallel and underestimation of the reliability on demand for systems with components logically arranged in parallel. The key reason for these discrepancies is the variability of components from the same type. Techniques for countering variability by promoting asymmetric response through inversion have also been introduced. The paper demonstrates that variability during assembly operations can affect negatively the reliability of mechanical systems. Accordingly, techniques for reducing the variability of stresses during assembly operations have been discussed. Finally, the paper provides a discussion related to the reasons for the relatively slow adoption of domain-independent methods for improving reliability despite their numerous advantages.

Keywords:

• Variability
• system reliability
• increasing the level of balancing
• domain-independent methods

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Michael Todinov

Michael Todinov is a professor of mechanical engineering at Oxford Brookes University, UK. Prof. Todinov pioneered research on reliability analysis based on the cost of failure, repairable flow networks, domain-independent methods for reliability improvement and engineering optimisation and generating new knowledge by reverse engineering of algebraic inequalities.