Reliability Engineering

13Reliability Estimation Techniques

Reliability is defined as “the ability of a product to function properly within specified performance limits for a specified period of time, under the life-cycle application conditions.” Reliability estimation techniques include methods to evaluate system reliability throughout the product life cycle. The major components of reliability estimation techniques are the test program and the analysis of data from the tests. Test programs are developed throughout the life cycle, that is, design, development, production, and service, to ensure that reliability goals are met at different stages in the product life cycle. Data from test programs during each stage are acquired and processed to evaluate the reliability of a product at each stage in the life cycle.

The purpose of reliability demonstration testing is to determine whether the product has met a certain reliability requirement with a stated confidence level prior to shipping. Tests should be designed to obtain maximum information from the minimum number of tests in the shortest time. To achieve this, various statistical techniques are employed. A major problem in the design of adequate tests is simulating the real-world environment. During its lifetime, a product is subjected to many environmental factors, such as temperature, vibration, shock, and rough handling. These stresses may be encountered singly, simultaneously, or sequentially, and there are many other random factors.

13.1 Tests during ...