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IEVref: | 192-05-06 | ID: | |

Language: | en | Status: Standard | |

Term: | instantaneous failure rate | ||

Synonym1: | failure rate [Preferred] | ||

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Symbol: | λ(t)
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Definition: | 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) $\lambda \left(t\right)=\underset{\text{\Delta}t\to 0}{\text{lim}}\frac{1}{\text{\Delta}t}\text{\hspace{0.17em}}\frac{F\left(t+\text{\Delta}t\right)\u2013F\left(t\right)}{R\left(t\right)}=\frac{f\left(t\right)}{R\left(t\right)}$ where Note 1 to entry: See IEC 61703, Note 2 to entry: Other terms used for instantaneous failure rate are: “hazard function”; “hazard rate”; and “force of mortality” (abbreviation FOM). | ||

Publication date: | 2015-02 | ||

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$\lambda \left(t\right)=\underset{\text{\Delta}t\to 0}{\text{lim}}\frac{1}{\text{\Delta}t}\text{\hspace{0.17em}}\frac{F\left(t+\text{\Delta}t\right)\u2013F\left(t\right)}{R\left(t\right)}=\frac{f\left(t\right)}{R\left(t\right)}$

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*(*t*_{1}, *t*_{2}) by *R*(*t*) = *R*(0, *t*).

Note 1 to entry: See IEC 61703, *Mathematical expressions for reliability, availability, maintainability and maintenance support terms*, for more detail.

Note 2 to entry: Other terms used for instantaneous failure rate are: “hazard function”; “hazard rate”; and “force of mortality” (abbreviation FOM).