Exam 14: Reliability

At ski resorts, lifts need to be reliable. Recently, one resort tested the reliability of their 20 different lifts by using a time-terminated test. The test ran for 100 hours of continuous operation. During the test, four lifts broke down, at 40, 65, 80, and 89 hours. Calculate the mean life of the lifts. If it takes on average 12 hours to repair a lift, calculate the availability of the lifts.

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Question 1

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$\lambda = - \frac { 4 } { 40 + 65 + 80 + 89 + 16 ( 100 ) } = 0.002$
$\Theta = 500$ hours of average life before breakdown. Availability $= \frac { 500 } { 500 + 12 } = 0.977$
The system is available $97.7 \%$ of the time.

Calculate the reliability of the following system.

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Question 2

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$R ( system ) = 0.99 \times [ 0.98 + 0.96 ( 1 - 0.98 ) ] R ( system ) = 0.99$
$R ($ system $) = 0.99 \times [ 0.98 + 0.96 ( 1 - 0.98 ) ]$
$R ($ system $) = 0.99$

Homes of the future are supposed to be able to automatically make your coffee, lock your doors, open and close your window shades and even track your healthy eating habits. One smart home system takes your words and turns them into to-do lists. So instead of making a mental not to add milk to your shopping list, you simply say out-loud 'remember milk'. The work 'remember' is picked up by a microphone in the wall and triggers a computer to transcribe your words to your to-do list. This list is downloaded automatically to you personal planning device (PPD). Calculate the reliability of the system.

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$\begin{array}{l} R(\text { system })=[0.98+0.75(1-0.98)] \times\{1-(1-0.90)(1-0.90)(1-0.90)\} \times 0.92 \times \\ 0.96 \times 0.85 \times[0.70+0.60(1-0.70)] \times 0.95\\\\R(\text { system })=0.62 \end{array}$
$\begin{array}{l}R(\text { system })=[0.98+0.75(1-0.98)] \times\{1-(1-0.90)(1-0.90)(1-0.90)\} \times 0.92 \times \\0.96 \times 0.85 \times[0.70+0.60(1-0.70)] \times 0.95\\\\R(\text { system })=0.62\end{array}$

Describe the product life cycle curve using a diagram to help your description. Give examples of types of failures that occur at each of the three phases of the diagram.

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Question 4

Calculate the reliability of the following system.

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Question 5

In order to prevent faulty product from reaching the consumer, a large computer chip manufacturer tests chips for 1,000 hours of operating time. For a typical mean-life test, 10 chips are selected at random from the daily production and submitted to the 1,000 hour life test. For this particular batch of 10 chips, three of the 10 showed he dame defect within the first few hours (50, 100, and 200 hours). The other chips completed the test. Calculate the mean-life of this production lot of chips.

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Question 6

Calculate the reliability of the following system.

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Question 7

Calculate the reliability of the following system.

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Question 8

A testing lab is using a time-terminated test to determine the life of a contact switch. The test of 15 switches lasts 150 hours. During the test, only one switch failed, at 30 hours. Calculate the mean life of the switches.

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Question 9

If you were hired as a reliability engineer, what would two of your day-to-day job activities?

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Question 10

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Calculate the reliability of the following system.

Describe the product life cycle curve using a diagram to help your description. Give examples of types of failures that occur at each of the three phases of the diagram.

Calculate the reliability of the following system.

Calculate the reliability of the following system.

Calculate the reliability of the following system.

A testing lab is using a time-terminated test to determine the life of a contact switch. The test of 15 switches lasts 150 hours. During the test, only one switch failed, at 30 hours. Calculate the mean life of the switches.

If you were hired as a reliability engineer, what would two of your day-to-day job activities?

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