Lect 11-18.pdf - Reliability Modeling Life Multpliers...

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Reliability Modeling
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Life Multpliers MIL-HDBK-217 is very well known in military and commercial industries. It is probably the most internationally recognized empirical prediction method, by far. The latest version is MIL-HDBK-217F, which was released in 1991 and had two revisions in 1992 and 1995. where: π S is the stress factor π T is the temperature factor π E is the environment factor π Q is the quality factor π A is the adjustment factor According to the handbook, the failure rate of a commercial ceramic capacitor of 0.00068 μF capacitance with 80% operation voltage, working under 30 degrees ambient temperature and "ground benign" environment is 0.0217x10 -6 hours.
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Failure Simulatons
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Random number generation using inverse transform The rule of probability integral transform states that if X is a contnuous random variable with cumulatve distributon functon F X , then the random variable Y = F X ( X ) has a uniform distributon on [0, 1]. The inverse probability integral transform is just the inverse of this.
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Let x be a random variable whose distributon can be described by the cumulatve distributon functon F(x) . We want to generate values of x which are distributed according to this distributon. The inverse transform sampling method works as follows: 1. Generate a random number u from the standard uniform distributon in the interval [0,1]. 2. Compute the value x such that F ( x ) = u . 3. Take x to be the random number drawn from the distributon f(x) described by F(x) . Random number generation using inverse transform
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Then, to generate a random tme from a Weibull distributon with a given η and β , a uniform random number from 0 to 1, U R [0, 1], is frst obtained. The random tme from a Weibull distributon is then obtained from F(t) = 1 – exp (-t/ h) b R(t) = 1 - F(t) = exp (-t/ h) b t = h {-ln ( U R [0,1])} 1/b Failure simulation using Weibull distribution
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Failure simulation applications: Warranty Analysis
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  • Fall '17
  • Makarand Kulkarni

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