The reliability function, R(t), defines the probability that a system or component will perform its required function without failure for a specified time ‘t’. For systems with a constant failure rate (λ), it is described by the exponential distribution: [latex]R(t) = e^{-\lambda t}[/latex]. This function is fundamental to predicting the longevity and performance of a product.
Reliability Function (Survival Function)
The reliability function, also known as the survival function, is the complement of the cumulative distribution function (CDF) of failure, F(t). That is, [latex]R(t) = 1 – F(t)[/latex]. It provides a time-dependent measure of a system’s ability to remain operational. The function always starts at R(0) = 1 (100% probability of survival at time zero) and monotonically decreases towards 0 as time approaches infinity.
A key related concept is the failure rate, or hazard function, [latex]h(t)[/latex], which represents the instantaneous probability of failure at time t, given that the system has survived up to that time. The relationship is given by [latex]h(t) = f(t) / R(t)[/latex], where f(t) is the probability density function of failure. The reliability function can be derived from the hazard function as [latex]R(t) = e^{-\int_{0}^{t} h(\tau) d\tau}[/latex].
In the special but common case of the exponential distribution, the failure rate [latex]\lambda[/latex] is constant. This ‘memoryless’ property implies that the age of the component does not affect its likelihood of failing in the next instant. This model is often applied during the ‘useful life’ phase of a product’s lifecycle, after initial defects have been weeded out and before wear-out mechanisms dominate.
النوع
Disruption
الاستخدام
Precursors
- probability theory developed by Pascal and Fermat
- actuarial life tables for calculating human mortality
- work on statistical distributions by mathematicians like Poisson and Gauss
- early quality control methods from the 1920s
التطبيقات
- calculating warranty periods for consumer electronics
- scheduling preventative maintenance for industrial machinery
- determining the probability of mission success for spacecraft
- assessing the long-term performance of medical implants
براءات الاختراع:
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Reliability Function (Survival Function)
(if date is unknown or not relevant, e.g. "fluid mechanics", a rounded estimation of its notable emergence is provided)
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