A Review of Systems Reliability Analysis Using Fuzzy Logic

Reliability And Failure Rate

Reliability is one of the important aspects of product quality that Murphy (2000) define reliability as follows:

The reliability of a product (system) is likely the product will carry out its mission for a specified period of time under environmental or normal conditions. Also reliability has several definitions:

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  The suitability of a device for a purpose at a specific time.

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  The capacity of the system or equipment to carry out the mission for which it is designed.

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  Resistance of the system or device to failure.

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  The probability that the unit in operation will be able to perform the desired task in a timely manner.

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  System capability for low cost failure.

Reliability is strongly dependent on the concept of failure. Many products will decline with increasing age and use and this naturally affects the reliability of the product. When the performance of the product falls below optimal levels then the product is called failure. The two definitions of failure are:

• 1.

  To finish the ability of a component to perform the required task (IEC50 (191), 1990).

• 2.

  Equipment failure is that the equipment is not capable of performing its intended operation under specified operating conditions for which it was designed (Nieuwhof, 1984).

Also the technical reliability is defined as follows (IEC60050-191, 1990): The ability of a component to perform the required task under the terms for a given time period.