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23reliability

# 23reliability - Reliability and Availablity This set of...

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Reliability and Availablity This set of notes is a combination of material from Prof. Doug Carmichael's notes for 13.21 and Chapter 8 of Engineering Statistics Handbook . NIST/SEMATECH e-Handbook of Statistical Methods, http://www.itl.nist.gov/div898/handbook/, 2005. available free from: see: NIST/SEMATECH e-Handbook of Statistical Methods on CD Including and improving reliability of propulsion (and other) systems is a challenging goal for system designers. An approach has developed to tackle this challenge: 1. a design and development philosophy 2. a test procedure for components and total systems 3. a modelling procedure based on test results, field tests and probability (statistics Design and development philosophy recognition that reliability is a product is essentiall the abscence of failures or substandard performance of all critical systems in the design, followed by an examination of the factors leading to failure. Causes of failure: a. loading: (inaccurate estimates of) thermal, mechanical or electriacl including vibrations b. strength: (inaccurate estimates of) the load carrying capacity of the components c. environment: presence of dirt, high temperature, shock, corrosion, moisture, etc. d. human factors: heavy handed operators ("sailor proof"), wrong decisions (operator error), criminal activities (sabatoge), poor design, tools left in critical components, use of incorect replacements e. quality control: or lack thereof; loose control of materials and manufacture, lack of inspection, loose specifications f. accident; act of God, freak accidents, collisions g. acts of war: terorism, war damage designer should recognize these potential causes for failure and try to design devices that will resist failure. Detailed Design Features a. try to account for all possible situations in the design stage and eliminate possible failures. Delivering maximumloads and minimum strengths b. assume that every component can fail, examine the outcome of the failure and try to reduce the risk of damage. Failure Modes and Effects Analysis (FEMA) c. institute strict quality control in manufacture and maintenance d. have cleaarly defined specifications (including material specifications and methods of testing) e. develop technology to meet new challenges. conduct development testing.

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23reliability - Reliability and Availablity This set of...

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