TECH SPOT: SAMPLE CRE QUESTIONS (PART 11)

1. Estimate the individual part failure rate given a base failure rate of  0.0333 failure/hour, a quality factor of 0.98 and an environmental stress factor of 0.92.

A. 0006

B. 0.300                      

C. 0.027                   

D. 0.0300

2. Consider a three component independent series system. The component reliabilities are described according to the following:

Component (1): Weibull (β = 1.6 η = 9,500)

Component (2): Exponential (λ = 0.000087)

Component (3): Lognormal (μ = 7.5 σ = 0.81) .

The reliability of the system at 1,000 hours is most nearly:

A. 0.6846 

B. 0.9995 

C. 0.3155  

D. 0.7673

3. A failure reporting and corrective action system should ensure that all steps are taken to :

A. Determine responsibilities for failures.

B. Record costs associated with the corrective action.

C. Identify, investigate and analyze failures.

D. Define the goals of the FRACAS team.?

4. The injection mold for a manufacturing process requires periodic maintenance due to the failure of a forming mechanism. The failures occur at a constant rate of 0.0002 per hour and the repairs occur according to a constant rate of 0.0625 per hour. The steady state probability of the system being operational is most nearly:

A. 0.0032  

B. 0.9998  

C. 0.9968  

D. 0.9375

5. Monte Carlo simulation is being used by a manufacturer to determine the probability of mechanical failure of a new design. Which of the following are required to perform this analysis?

I. Computer‐generated random numbers

II.  Stress distribution

III. Strength distribution                                        

IV.  Environmental conditions

A.   I         

B. I, II, & III     

C. All of the Above    

D. II  &  III

6. What is the best description for a Reliability Program and Reliability Information?

A. Reliability Program is more effective without Reliability Information

B. Reliability Program has nothing to do with Reliability Information.

C. Reliability Program only collects Reliability Information.

D. Reliability Program utilizes Reliability Information to improve reliability.

7. Consider the following Reliability Block Diagram:

Success will occur even if a failure occurs in the following elements?

A. I & IV  

B. I & III  

C. II & III  

D.  I & II

8. An electronic system needs any 2 out of 4 serial power supplies to be operational.

What is the reliability of this 2 out of 4 power supply design? Assuming the switching has 100% reliability.

Each power supply has the same reliability of 95%. All power supplies are activated during system operation.

A. 0.8095    

B. 0.9095    

C. 0.9595    

D. 0.9995

9. The system reliability of an active redundant or parallel system:

A. is greater than the reliability of any subsystem.

B. is equal to the reliability of the ‘best’ subsystem.

C. decreases as more redundant subsystems are added to the system.

D. increases if the subsystem with the lowest reliability is removed.

10. Given a set of test data for estimating wear‐out reliability of a mechanical part design (assuming normal distribution of the data), which of the following factors is NOT required to obtain a reliability estimate at 90% confidence level?

A. Number of Degrees of Freedom (DF)

B. Standard deviation of the population

C. Standard error of the mean

D.  Z‐score for the specified confidence level

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