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Reliability (continued)

Reliability (continued). warranty periods: reliabilities relative to specified length of time. The Bathtub Curve. Distribution and Length of Phase. To properly identify the distribution and length of each phase requires collecting and analyzing historical data

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Reliability (continued)

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  1. Reliability (continued) warranty periods: reliabilities relative to specified length of time.

  2. The Bathtub Curve

  3. Distribution and Length of Phase To properly identify the distribution and length of each phase requires collecting and analyzing historical data The mean time between failures (MTBF) in the infant mortality phase can often be modeled using the negative exponential distribution

  4. Exponential Distribution

  5. Example. If a vac cleaner’s reliability has an exponential distribution, with MTBF = 4 years. Find the probability that one of these cleaners will have a life that ends a) After the initial four years of service

  6. In our example, T = 4 years MTBF = 4 years So, T/MTBF = 1

  7. Table 4S.1 Page 174

  8. Table 4s.1: e - 4 / 4 = .3679

  9. Example. If a product has MTBF = 4 years. Find the probability that one of these cleaners will have a life that ends b) Before four years of service are completed Table 4s.1: e - 4 / 4 = .3679 Solution for b) 1 - e - 4 / 4 = 1-.3679 = 63.21%

  10. Availability Availability The fraction of time a piece of equipment is expected to be available for operation

  11. Example– Availability John Q. Student uses a laptop at school. His laptop operates 30 weeks on average between failures. It takes 1.5 weeks, on average, to put his laptop back into service. What is the laptop’s availability?

  12. Homework: Page 180 Ex 1. a). Page 181. EX 14. a) b)

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