Breakthroughs in Reliability#

These landmarks trace a conceptual development from a physical law to a useful engineering model. The order is a learning path, not a dated chronology or a claim that any idea had a single inventor. SI units apply unless documented otherwise.

Survival analysis: failures become distributions#

Reliability is the probability of surviving beyond a time. A constant hazard gives the exponential model, while Weibull shape permits increasing or decreasing hazard.

\[R(t)=e^{-(t/\eta)^\beta}\]

Use engineeringkit.reliability.weibull_reliability to explore the model. Time and scale must share units; fitting a distribution and checking censoring are outside these algebraic helpers.

Redundancy: system architecture changes survival#

Series systems require every component to survive; parallel systems need at least one. Their simple product expressions make independence a critical modeling assumption.

\[R_s=\prod_i R_i,\qquad R_p=1-\prod_i(1-R_i)\]

Use engineeringkit.reliability.parallel_reliability to explore the model. Common-cause failures violate independence and can sharply reduce the benefit of redundancy.

Repair: availability answers a different question#

A repairable system can fail repeatedly yet be available for most of its lifetime. Steady availability combines mean operating time and mean repair time.

\[A=MTBF/(MTBF+MTTR)\]

Use engineeringkit.reliability.availability to explore the model. This long-run alternating-renewal ratio is distinct from the probability of no failure during a mission.

Explore and verify#

Reliability: distributions, independence and rate units records units, conventions and independent checks. Compare the gallery output against the equations before extending a model.

Redundancy under independent failures

Redundancy under independent failures

Weibull survival and shape

Weibull survival and shape

Further reading#

University or agency teaching reference provides background beyond the implemented subset. The equations and examples here are concise original explanations, not reproductions of that reference.