RAM Advanced Techniques & Methods 2 — Questions and Answers
Question 1: Which accelerated life testing (ALT) model assumes a linear relationship between the log of the acceleration factor and the reciprocal of absolute temperature?
- Eyring model
- Arrhenius model (Correct answer)
- Inverse power law model
- Coffin-Manson model
Correct answer: Arrhenius model
The Arrhenius model relates failure rate to temperature via an exponential function of 1/T, making log(AF) linear in 1/T.
Question 2: In reliability block diagram (RBD) analysis, what configuration yields the highest system reliability for the same set of components?
- Series configuration
- Parallel configuration
- k-out-of-n configuration with k=n
- Standby redundancy with cold standby (Correct answer)
Correct answer: Standby redundancy with cold standby
Cold standby redundancy yields the highest reliability because standby units do not accumulate failure hours until switched in, unlike active parallel units.
Question 3: What does the 'beta' parameter in a Weibull distribution indicate when its value is less than 1?
- Random failures dominating
- Wear-out failures dominating
- Infant mortality failures dominating (Correct answer)
- Constant hazard rate
Correct answer: Infant mortality failures dominating
A Weibull shape parameter β < 1 indicates a decreasing hazard rate, characteristic of infant mortality or early-life failure modes.
Question 4: Which RAM analysis technique uses Monte Carlo simulation to propagate uncertainty through a reliability model?
- FMEA
- Fault tree analysis
- Probabilistic risk assessment (PRA) (Correct answer)
- Root cause analysis
Correct answer: Probabilistic risk assessment (PRA)
Probabilistic risk assessment uses Monte Carlo simulation to propagate parameter uncertainties and quantify the distribution of system risk metrics.
Question 5: A system has MTBF of 500 hours and MTTR of 10 hours. What is its steady-state availability?
- 0.9804 (Correct answer)
- 0.9800
- 0.9500
- 0.9950
Correct answer: 0.9804
Steady-state availability = MTBF / (MTBF + MTTR) = 500 / (500 + 10) = 500/510 ≈ 0.9804.
Question 6: In the context of maintainability, what does the Mct (mean corrective maintenance time) specifically measure?
- Total calendar time for all maintenance tasks
- Average active repair time excluding logistics delays (Correct answer)
- Time from failure detection to system restoration including all delays
- Scheduled downtime for preventive maintenance
Correct answer: Average active repair time excluding logistics delays
Mct measures only the active hands-on corrective maintenance time, excluding administrative and logistic delay times.
Question 7: Which technique decomposes system unreliability into minimal cut sets to identify the most critical failure combinations?
- Event tree analysis
- Fault tree analysis (Correct answer)
- FMECA
- Markov analysis
Correct answer: Fault tree analysis
Fault tree analysis (FTA) systematically identifies minimal cut sets — the smallest combinations of basic events that cause the top event (system failure).
RAM Advanced Techniques & Methods 2
Which accelerated life testing (ALT) model assumes a linear relationship between the log of the acceleration factor and the reciprocal of absolute temperature?