الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Reliability is the probability of a unit to achieve a required task, under given environmental and operational circumstances during a specific time. Most of the workers in the field of reliability have considered reliability as a function of time. It is well known that the constituent components of an industrial or defense equipment, while in operation, are generally subjected to a certain stress level and also that the components are capable of withstanding these stresses (environmental or due to conditions prevailing within the equipment) up to a certain limit only, i.e. the components possess some rated strength to withstand these stresses. If the stress level exceeds the rated value of the components’ strength, the component will fail to work. This fact was practically realized during the second world war when it was found that defense equipment like radar and electronic communication systems which were quite reliable otherwise, failed to perform their functions adequately and efficiently when made to function under environmental conditions adverse to those for which these were designed.