01_Introduction to Reliability Engg_r1.doc

Wrong plane then the reliability of the procedure

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wrong plane, then the reliability of the procedure concerns the probability that it will be on the correct airplane. The specified conditions are often environmental, but they can also encompass energy levels, speeds, personal or any combination thereof. The specified time may be the actual time measurements like hours, days, years and so on, or it may be a specified number of operation cycles, or even the single use of a disposable item. Reliability is a prediction of the probability of success, based upon available data and resulting from observations and tests. Reliability 3
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Introduction to Reliability engineering testing and observations produce a probability that is expressed as a percent. However, that number is only a prediction. The reliability prediction may help to determine the feasibility of a new design or manufacturing process, so that a decision can be made as to whether or not to pursue it. It also helps to compare two or more products, processes or systems to determine which one will last long or have the highest success. Often reliability qualifies a new vendor or manufacturing process. A reliability prediction may even be a selling point that induces a customer to choose your product over competitors. Reliability can also be the probability of successfully completing a multi-task mission. Think of the space shuttle bringing a satellite into space and returning. This is a process of involving the interaction of all the applicable hardware, software, people and procedures necessary to complete the space shuttle mission. Each of these is a component of the mission completion system and each has its own component reliability. Together they give the mission reliability, that is, the probability that the space shuttle will successfully put satellite into the correct orbit and return safely. Brief History Early foundations of reliability may be found in actuarial concepts used in the insurance industry, particularly in the study of human survival probabilities. The study of structural reliability and fatigue failure began in 1930’s and has since continued. One of the first areas of reliability to be approached with any mathematical sophistication was the area of machine maintenance. Queuing and renewal theory techniques were used early on to solve problems involving repair and inspection. In 1939, Weibull proposed a distribution, while analyzing the fatigue life of materials, later named after him. Although, the earlier work of 1930’s and 1940’s queuing and renewal theory using exponential distribution provided some of the mathematical foundations of reliability, it was not become an independent subject of study until World War II.
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