reliability 1. probability a product will perform as promoted for a given time period under given...
Post on 19-Dec-2015
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Reliability
1
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
2
Inherent Reliability is Designed Reliability
• Found by reliability testing
3
Achieved Reliability is Empirical
4
Infant Mortality Period: if it makes it by time x, then the constant failure rate takes
over
5
Failure Rate, lambda, is units per hour
• lambda = number of failures/total unit operating hours
6
Mean Time to Failure MTTF (non repairable) or Mean Time
Between Failure MTBF (repairable items) is theta =
1/lambda
7
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
8
Reliability Function R of given time (RT = e^(-lambda * T)
9
Reliability of process with Tasks in Serial
• R1 times R2… times RN
10
Reliability of process with steps in parallel
• 1-(1-R1)(1-R2)(1-Rn)
11
Redundancy and Apollo 13
12