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Reliability

Reliability. 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

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Reliability

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  1. Reliability

  2. 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

  3. Inherent Reliability is Designed Reliability • Found by reliability testing

  4. Achieved Reliability is Empirical

  5. Infant Mortality Period: if it makes it by time x, then the constant failure rate takes over

  6. Failure Rate, lambda, is units per hour • lambda = number of failures/total unit operating hours

  7. Mean Time to Failure MTTF (non repairable) or Mean Time Between Failure MTBF (repairable items) is theta = 1/lambda

  8. 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

  9. Reliability Function R of given time (RT = e^(-lambda * T)

  10. Reliability of process with Tasks in Serial • R1 times R2… times RN

  11. Reliability of process with steps in parallel • 1-(1-R1)(1-R2)(1-Rn)

  12. Redundancy and Apollo 13

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