TECH SPOT: SAMPLE CRE QUESTIONS (Part 16)

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1. The usual consequences of management assuming human error as the “root cause” of a failure is
A. Repeat of the same failure
B. Disciplinary action for the employee
C. Less productivity
D. All of the above

 

2. “Burn-in” testing is conducted on electronic assemblies for systems to:
A. Establish system failure rate.
B. Extend product life
C. Increase the total number of failure occurrences.
D. Minimize early life failure occurrences.

 

3. When testing to establish failure rate and reliability predictions, which of the following is not normally a feasible acceleration factor with respect to rated conditions:
A. Longer time
B. Greater humidity
C. Higher temperature
D. Higher voltage

 

4. The Time to Failure(B. TTF) for a component is normally distributed with μ = 310 hrs and σ= 42hrs at a temperature of 130F.
The normal operating temperature is 75F.
What is the reliability at time=310 hrs under normal operating conditions given an acceleration factor of 1.8 between temperature 75F and 130F?
A. 0.5
B. 0.7541
C. 0.9995
D. none of these.

 

5. What is meant by “Fail Safe Design”?
A. Designed such that a failure will not adversely affect the safe operation of the system
B. Designed such that the failure probability is low if the system is operated safely.
C. Designed such that the system cannot fail if operated safely,
D. All of the above

 

6. Humans will perform tasks more reliably if:
1. They understand what is required and why
2. The task is challenging and complex
3. Pressure is applied which penalizes failure
4. There are incentives for quality

A.1 only
B. 1 & 2
C. 1 & 3
D. 1 & 4

 

7. Five items were placed on test, one item failed after 42 hrs, and the remaining four items were removed after 50 hrs.
It is known that the time to failure for these items follows a Weibull with β=2.2.
Determine the 95% lower confidence limit for the characteristic life.
A. 13.5 hrs
B. 39.8 hrs
C. 49.7 hrs.
D. None of the above

 

8. What is one of the important considerations in design work when regarding human factors in reliability?
A. The establishment of good storage and shelf life,
B “idiot proofing”
C. Production personnel being able to fabricate parts
D. Knowing the correlation between environmental factors and performance

 

9. A failure PDF for Lawn mower engine is assumed to be a Weibull distribution with β= 4.5 and η = 9.3 years.
What is the design life at a reliability of 90%?
A. 4.82 yrs
B. 5.64 yrs
C. 6.66 yrs
D. 3.35 yrs

 

10. An engineer just ran 50 compressor start tests with no failures, he needs to pass the customer’s requirement of 80% confidence of 0.90 reliability.
Has he done that?
A. Yes
B. Almost
C. No way

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