measures for reliability related conceptsMessgrößen für Funktionsfähigkeitskonzepte

operating time accumulated from the first use, or from restoration, until failure

operating time accumulated from the first use until failure

duration between consecutive failures

operating time accumulated between consecutive failures

probability of performing as required for the time interval (t1, t2), under given conditions

limit, if it exists, of the quotient of the conditional probability that the failure of a non-repairable item occurs within time interval (t, t + Δt) by Δt, when Δt tends to zero, given that failure has not occurred within time interval (0, t) λ(t)=limΔt→01Δt F(t+Δt)–F(t)R(t)=f(t)R(t) λ(t)=limΔt→01Δt F(t+Δt)–F(t)R(t)=f(t)R(t) where F(t) and f(t) are, respectively, the distribution function and the probability density at the failure instant, and where R(t) is the reliability function, related to the reliability R(t1, t2) by R(t) = R(0, t).

average value of the instantaneous failure rate over a given time interval (t1, t2) λ¯(t1, t2)=1t2−t1∫  t2  t1λ(t) dt λ¯(t1, t2)=1t2−t1∫  t1  t2λ(t) dt

limit, if it exists, of the quotient of the mean number of failures of a repairable item within time interval (t, t + Δt), by Δt, when Δt tends to zero z(t)=limΔt→0+E[N(t+Δt)−N(t)]Δt z(t)=limΔt→0+E[N(t+Δt)−N(t)]Δt where N(t) is the number of failures in the time interval (0, t), where E denotes the expectation.

average value of the instantaneous failure intensity over a given time interval (t1, t2)

limit, if it exists, of the instantaneous failure intensity z(t), when time t tends to infinity

expectation of the operating time to failure

expectation of the operating time to first failure

expectation of the duration of the operating time between failures Note 1 to entry: