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Reliability Basics
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C. E. Ebeling, Reliability and maintainability engineering, Tata McGraw Hill, 2 nd Ed., 2009 Patrick O'Connor, A. Kleyner, Practical Reliability Engineering, Wiley India, 5 th Ed., 2012 Guangbin Yang, Life Cycle Reliability Engineering, John Wiley & Sons, Inc. Reliability Books
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The answer is simple. If a system has poor reliability, a mission may not get completed, a customer may get dissatisfied, a company may loose reputation Why do we need reliability ?
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Probability that a bearing of type ABC will survive 10000 cycles of continuous operation under a load which is 10% of its dynamic load rating without failure (Failure Criteria: noise level > 70 dB and/or bearing temperature > 75 o C) with the required lubricant viscosity maintained between 25 and 35 mm 2 /s, contaminant particle size less than 6 μ m and dissolved moisture content in lubricant less than 300 ppm. Reliability Definition: Example
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Probability that a weapon continuously fires 5000 rounds when operated in the prescribed manner (as per operator’s manual) in desert environment with planned stoppages of 30 min every 500 rounds is 0.95. Reliability Requirement: Example Environment definition: Temperature, humidity, dust levels etc.
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There are two products of the same type but different brand. For one product, R(100 hrs) = 0.95 For the other product, R (150 hrs) = 0.90 Which product is better ? Reliability Comparison
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System Reliability
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Series Systems R S = R 1 R 2 ... R n 1 2 n A system can have different configurations
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Parallel Systems R S = 1 - (1 - R 1 ) (1 - R 2 )... (1 - R n ) 1 2 n A system can have different configurations
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Series-Parallel Systems Convert to equivalent series system A B C C D R A R B R C R D R C A B C’ D R A R B R D R C’ = 1 – (1-R C )(1-R C ) A system can have different configurations
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R = ? 0.99 0.95 0.90 0.95 0.95 0.95 0.99 0.90 0.90 0.99 Example Consider a multi stage production line with multiple machines at each stage. Find the reliability of this line if the reliability of each machine for the given period is known.
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i-out of-m Systems Consider five identical mining equipment at a site. Since this is a remote location, it takes
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  • Fall '17
  • Makarand Kulkarni

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