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 Maintainability: related to durability and refers to once a product breaks, what is the probability it can become functional again

Inherent Reliability is Designed Reliability Found by reliability testing

Achieved Reliability is Empirical

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

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

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

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

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

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

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

Redundancy and Apollo 13