CRE Reliability Fundamentals 2

Question 1

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

Accepted Answer

e^(-0.2) ≈ 0.819

Answer

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

Question 2

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

Accepted Answer

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

Answer

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

Question 3

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

Accepted Answer

Infant mortality or early failures

Answer

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

Question 4

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

Accepted Answer

Repairable systems with random failures

Answer

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

Question 5

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?

Accepted Answer

Rayleigh distribution

Answer

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

(CRE) Certified Reliability Engineer Practice Test

(CRE) Certified Reliability Engineer Practice Test

CRE Reliability Fundamentals 2