Slides - Åbo Akademi

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Exponential Distribution (cont.) The exponential distribution is often used in calculations as they are thus made much simpler During the useful-life stage, the failure rate is related to the reliability of the component or system by exponential failure law Describes neither the case of early failures (decreasing failure rate) nor the case of worn-out components (increasing failure rate)
MTTF Example A system with a constant failure rate of 0.001 failures per hour has a MTTF of 1000 hours. This does not mean that the system will operate correctly for 1000 hours! The reliability of such system at a time t is: R(t) = e −λt Assume that t = MTTF = 1 λ R(t) = e −1 ≈ 0.37 Any given system has only a 37% chance of functioning correctly for an amount of time equal to the MTTF (i.e., a 63% chance of failing in this period).
Page 1 and 2: Software Safety Lecture 8: System R
Page 3 and 4: Reliability Definition Reliability:
Page 5 and 6: Safety-critical Systems • Pervasi
Page 7 and 8: Hardware Failures The system is sai
Page 9 and 10: Failure Rate (ctd.) Classification
Page 11 and 12: Most Important Distributions Discre
Page 13 and 14: Reliability Parameters MTTF: Mean T
Page 15: Exponential Distribution The distri
Page 19 and 20: Example: Failure Rate Calculation F
Page 21 and 22: Series Systems Such a configuration
Page 23 and 24: Series-Parallel Combinations The mo
Page 25 and 26: M-of-N Arrangement A system consist
Page 27 and 28: Failure rate The term failure inten
Page 29 and 30: Design diversity Each variant of so

Slides - Åbo Akademi

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