ENMA 420-520 Lecture 11 Slides

ENMA 420-520 Lecture 11 Slides - Click to edit Master...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Click to edit Master subtitle style 10/17/09 Statistical Concepts for Engineering Management ENMA 420 / 520 Lecture #11 Product and System Reliability 11 10/17/09 Definitions Reliability: the probability that the product will meet a set of specifications for a given time Failure time: a random variable that represents the length of time T a product performs to specifications. The density function of T is called the failure time distribution f(t). 22 10/17/09 Reliability and Failure Time The probability that a product will fail before time t0 is the cumulative distribution function F(t0): Then reliability can be defined as: 33 lll = l ==== l ======= & = lll l = 1 === l 10/17/09 Hazard Rates Define events A and B: A: Item fails in the interval (t, t + &t) B: Item survives until time t then P(A|B) = P(A[B) / P(B). However, if the item fails in the interval (t, t + & t) then it must have survived until time t so P(A|B) = P(A) / P(B). For sufficiently small &t this is approximated by: 44 lll ll = ==== l 1 = (= ) = ==== l l (= ) l (= )= ==== = (= ) 10/17/09 Hazard Rates (Contd) A constant hazard rate implies that the item never gets fatigued (also called a memoryless distribution). Example: exponential distribution has a hazard rate of 1/ Often appropriate for maintained systems systems whose parts are replaced on an ongoing basis so the overall hazard rate remains constant 55 10/17/09 Hazard Rates (Contd)...
View Full Document

This note was uploaded on 10/17/2009 for the course MET 387 taught by Professor Dean during the Spring '09 term at Old Dominion.

Page1 / 23

ENMA 420-520 Lecture 11 Slides - Click to edit Master...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online