Reliability Fundamentals Flashcards

A system has a constant failure rate of 0.002 failures per hour. What is the probability of surviving 100 hours of operation?

Answer: e^(-0.2) ≈ 0.819

For a constant failure rate λ, reliability R(t) = e^(-λt) = e^(-0.002×100) = e^(-0.2) ≈ 0.819.

Which of the following best describes the 'bathtub curve' in reliability engineering?

Answer: A plot of failure rate over time showing early failures, constant rate, and wear-out

The bathtub curve shows three phases: infant mortality (decreasing failure rate), useful life (constant rate), and wear-out (increasing rate).

What does the Weibull shape parameter β < 1 indicate about a failure mode?

Answer: Infant mortality or early failures

A Weibull shape parameter β < 1 indicates a decreasing hazard rate, characteristic of infant mortality failures.

Mean Time Between Failures (MTBF) is most appropriately applied to which type of system?

Answer: Repairable systems with random failures

MTBF applies to repairable systems, representing the average time between successive failures during random-failure life.

A reliability engineer notices that the hazard rate of a component is proportional to time (h(t) = kt). Which distribution best models this failure behavior?

Answer: Rayleigh distribution

The Rayleigh distribution (Weibull with β = 2) has a hazard rate that increases linearly with time, h(t) = t/η².

In reliability block diagrams, what is the reliability of two components with reliabilities R₁ = 0.9 and R₂ = 0.8 connected in series?

Answer: 0.72

For series systems, system reliability is the product of component reliabilities: R_sys = 0.9 × 0.8 = 0.72.

Which reliability metric measures the probability that a system will be available for use at a random point in time?

Answer: Steady-state availability

Steady-state availability A = MTBF / (MTBF + MTTR) represents the long-run fraction of time a system is operational.