Reliability prediction using the concept of relevant-condition parameters

The classical approach to the calculation of reliability characteristics is based on the probability distribution of time to failure. Recently, a new approach based on relevant condition parameter was introduced, which describes the condition of the system and calculates the reliability characteristics at every instant of operating time. A condition parameter could be any characteristic such as crack, corrosion, vibration etc., that is directly or indirectly connected with an item of the system and its performance, and describes the condition of the item during the operating life. A condition parameter, whose numerical value fully describes and quantifies the condition of the item at every instant of operating time is called a relevant condition parameter. It is applicable to those systems whose components fail gradually. A failure mechanism such as cracks and corrosion fall under this category. This approach exploits the fact that for a system, as a whole and its components, to be capable of functioning, their relevant condition parameter must lie between certain limits defined by the initial value RCP/sub i//sup in/ and limiting value RCP/sub i//sup lim/, i=1, 2, ..., n. Particular numerical values for these intervals are set by design and manufacture.