1. The Arrhenius model is used to predict part reliability. Which of the following are valid Arrhenius model statements?

I. The rate of chemical reaction doubles for every 10°F rise.

II. It is useful for all accelerated testing plans.

III. It is useful for significant thermal stresses.

IV. It provides a relationship of failure to temperature.

A. I and II only

B. II and III only **C. III and IV only **D. I, III and IV only

2. A fault tree analysis (FTA) is a design analysis technique constructed from a “top event”. A basic problem with

this technique in comparison to a FMECA would be which of the following?

A. Assigning probabilities to the various events. **B. Needing a different FTA for each defined top event.**C. Understanding logical symbols.

D. Only electronic systems can be analyzed.

3. Subcontractor ABC has provided a new canister design. The canisters are rated at 1000 psi, with a standard deviation of 150 psi.

The expected stress will be 750 psi with a standard deviation of 200 psi.

What is the probability of failure of the canister ?

A. 0.3085 **B. 0.1587 **C. 0.1056

D. 0.0228

4. Which of the following is required to establish a reliability specification ?**A. The usage environment. **B. A robust design.

C. The reliability policy.

D. A mathematical model..

5. Using the failure data below, determine what distribution fits best from an engineering standpoint:

A. Lognormal,

B Smallest Extreme value,

C. Normal, **D. 3-parameter Weibull**

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6. Who should be chairperson of a design review committee ?

A. A senior member of management.

B. The chief designer.**C. The person best able to make decisions on a design. **D. The reliability engineer

7. The design system predicted B.1 life for a part is 1000 hours. Five parts have accumulated 1500 hours and five have 2000 hours without any failures.

If most parts of this type have a failure mode with a Weibull β = 3.0, is this success data sufficient to increase the predicted design life?

A. YES, **B. NO**(Hint: see USAF Weibull Handbook, 1983, Chapter 4 – Weibayes)

8. Ten failures occurred in the field out of a population of 2000. The ten failure times are: 51, 79, 116, 164, 197, 230, 232, 327, 414, and 451 hours.

Generate a Weibull distribution that best represents the total population

(Hint: see USAF Weibull Handbook, 1983, pp 127ff)**Answer: β=1.84, η= 4027hrs**

9. Maintainability considerations are important in the design of :

A. Unmanned satellites.

B. Integrated circuits.**C. Modern automobiles. **D. Consumer televisions.

10. A stress test was conducted for a mechanical part by subjecting a sample of 25 parts to increasing load stress.

The results of the test are identified in the table.

The sample was subjected to a 50% added stress each week for 5 weeks.

The test terminated after 5 weeks.

To determine whether failures observed in the test reflect actual use failures or are the result of high test stresses, which of the following must be known ?

A. The geometry of the test setup.

B. The precise history of cumulative stress.

C. The exact times of the failures. **D. The mechanisms of the failures.**

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