Reliability 1. Probability a product will perform as promoted for a given time period under given...
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![Page 1: Reliability 1. Probability a product will perform as promoted for a given time period under given conditions Functional Failure: does not operate as designed.](https://reader030.fdocuments.net/reader030/viewer/2022032800/56649d365503460f94a0dd61/html5/thumbnails/1.jpg)
Reliability
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Probability a product will perform as promoted for a given time period under
given conditions
• Functional Failure: does not operate as designed
• Reliability Failure: does not operate as designed as long as it is supposed to
• Maintainability: related to durability and refers to once a product breaks, what is the probability it can become functional again
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Inherent Reliability is Designed Reliability
• Found by reliability testing
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Achieved Reliability is Empirical
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Infant Mortality Period: if it makes it by time x, then the constant failure rate takes
over
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Failure Rate, lambda, is units per hour
• lambda = number of failures/total unit operating hours
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Mean Time to Failure MTTF (non repairable) or Mean Time
Between Failure MTBF (repairable items) is theta =
1/lambda
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For a given p of failure, what is the p of failure in a given time interval p = e ^ (-
lambda (t2-t1))
• number happening in given time that is Poisson distributed which means the interval between is exponentially distributed
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Reliability Function R of given time (RT = e^(-lambda * T)
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Reliability of process with Tasks in Serial
• R1 times R2… times RN
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Reliability of process with steps in parallel
• 1-(1-R1)(1-R2)(1-Rn)
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Redundancy and Apollo 13
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