Components in pressure vessels and pipes are usually subjected to mechanical and thermal cyclic loadings, which cause fatigue failure. The statistic and probabilistic assessmentof these components based on S-N or S — N curves is of great importance for fatigue design. Recently, the standard practice, as adopted by ASTM, BS, DNV and many other standards, for statistical analysis of linear or linearized stress-life (S-N) and strain-life (ε— N) fatigue data has been critically reviewed. The shortcomings of the standard procedure based only on the variation of cycles have been clearly demonstrated by examining the general trend of a large amount of S-N data. A new deterministic statistical method based on the equivalency between the changes of stress range and cycles to failure has been subsequently proposed and validated. In this paper a probabilistic approach based on the equivalency method is developed to quantify the uncertainty of engineering structures subjected to inherent randomness in material properties, and its effectiveness is also demonstrated.
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