## Reliability Engineering Training Reviews – Test your knowledge in Reliability related topics – Reviews

1) A system was up and working for 10,000 hours. During this period, 5 breakdowns were detected. What is the average or Mean Time Between Failures (MTBF) for this system.

1. 9995 hours
2. 10005 hours
3. 2000 hours
4. None of the above

2) ________ is literally the average time elapsed from one failure to the next.  Usually people think of it as the average time that something works until it fails and needs to be exchanged or repaired (again).

1. Mean Time Between Failures (MTBF)
2. Mean Time To Repair (MTTR)
3. Mean Time To Failures (MTTF)
4. Total down time

3) _____________is the average time that it takes to repair something after a failure.

1. Mean Time To Repair (MTTR)
2. Total down time
3. Mean Time To Failures (MTTF)
4. Mean Time Between Failures (MTBF)

4) ________ for repairable devices can be defined as the sum of MTTF plus MTTR. In other words, the it is the time from one failure to another.  This distinction is important if the repair time is a significant fraction of MTTF.

1. Mean Time To Repair (MTTR)
2. Mean Time To Failures (MTTF)
3. Mean Time Between Failures (MTBF)
4. Total down time

5) A light bulb in a chandelier is not repairable so light bulb will be replaced when it fails).  The MTTF for the light bulb is 10,000 hours.  The reliability for the light bulb is calculated as 81.2%. What does this mean?

1. 82% of the units will still be failure free. 18.8 % will have failed.
2. 18,8 % of the units will still be failure free. 81.2% will have failed.
3. 100% of the light bulbs will fail after 1880 hours of operation.
4. 100% of the light bulbs will fail after 8120 hours of operation.

6) Without oil changes, an automobile’s engine may fail after 150 hours of highway driving – that is the ______________.

1. Mean Time To Repair (MTTR)
2. Mean Time To Failures (MTTF)   (Someone might argue that MTBF can also be an answer; that can be discussed and maybe yes)
3. Mean Time Between Failures (MTBF)
4. Total down time

7) Assuming it takes 6 hours to remove and replace a pump and MTBF of the pump is 5000 hours. What is the MTTF for this failure?

1. 4994 hours
2. 5006 hours
3. 4669 hours
4. 5012 hours

8) The relationship between failure rates, predicted reliability, and MTBF can be summed up with the exponential formula

What is the predicted reliability for a unit that has a useful life of 5 years and an MTBF rating of 500,000 hours?  (a year=365 days)

1. 961
2. 916
3. 786
4. 100,000

9) Suppose 10 power supply devices were  tested for 500 hours. During the test 2 failures occur.

What is the MTBF of the power supply?

1. 2000 hours/failures
2. 2500 hours/failures
3. 100 hours/failures
4. none of the above

10) What is the MTTF of the same power supply?

1. 500 hours/failures
2. 100 hours/failures
3. 5000 hours/failures
4. none of the above

11) The useful life of a device is guaranteed as 2.3 years at 24 hrs/day, 7 days/week,356 days/year.   150 units were run for the useful life of the device in a lab and 50 units failed during the last hour.

What is the MTBF for this device?

1. 10,000
2. 15,000
3. 60,000
4. 100,000

12)  If a UAV takes an average of six months to fail and it takes 20 minutes, on average, to return the UAV  to its operational state , what is the then the UAV availability?

1. 99,9992%
2. 99,992%
3. 92%
4. 2%

13) Which of the following logical laws is true?

1. A + (B + C) = (A + B) • C
2. A + (B • C) = A + B •  A + C
3. A • (B + C) = (A • B) + (A • C)
4. A • (A + B) = B

14) _________ is a systems analysis tool. It offers a wide range of capabilities. It calculates system failure, frequency values and unavailability. In addition to component libraries, commonly used failure models can be stored and retrieved for repeated use.

1. Reliability Block Diagram (RBD)  [FTA can also be an answer; FTA is an example of adopting the concept of Negative logic and RBD is an example of adopting the concept of Positive logic.When you work on a method developed through the concept of negative logic such as FTA, it is very important that you understand that it is all about the failures and what will occur after the failures.
If you want to describe it in then term of the positive logic, you can use RDB]
2. Fault Tree Analysis (FTA)
3. The MIL-217
4. NSWC

15) _________is a systems reliability assessment tool, which focuses on failure path representation. It provides a wide variety of both qualitative and quantitative information about the system reliability and availability and are used during Reliability and Safety Risk Assessments to graphically represent the logical interaction and probabilities of occurrence of component failures and other events in a system.

1. Reliability Block Diagram (RBD)
2. Fault Tree Analysis (FTA)
3. The MIL-217
4. NSWC

16) _______ supports two methods of reliability prediction, calculates the failure rates and MTBF for electronic components, sub-systems, and systems. It can aid in locating areas for potential reliability improvement, as described in  Part Stress and Analysis and Parts Count. The Part Stress Analysis requires more detailed information and is usually applicable later in the design phase. The Parts Count generally requires less information, typically part quantities, quality levels and the application environment. It is most applicable early in the design phase and during proposal formulation.

1. Reliability Block Diagram (RBD)
2. Fault Tree Analysis (FTA)
3. The MIL-217
4. NSWC

16) ________ uses a series of models for various categories of mechanical components to predict failure rates based on temperature, stresses, flow rates and various other parameters. It provides models for various types of mechanical devices including springs, bearings, seals, motors, brakes and clutches. It  is a relatively new standard, and is currently the only one of its kind and is a commonly used model for mechanical components. Standard procedures for predicting the reliability of mechanical components, sub-systems and systems are defined in the Naval Surface Warfare Center Handbook of Reliability Prediction Procedures for Mechanical Equipment.

1. Telcordia (Bellcore)
2. IEC 62380 (RDF 2000)
3. The MIL-217
4. NSWC