FATIGUE RELIABILITY FORMULATION AND ANALYSIS

CYCLES is a computer program that computes the fatigue reliability of mechanical components. It includes a rather flexible model of uncertainty, both in distribution parameters of randomly varying quantities (e.g., load environment parameters such as wave height) and in uncertain material properties (e.g .. S-N fatigue properties). The formulation is intended to be or general applicability across a range of fatigue problems. Applications are shown here to offshore structures and wind turbines, both of which may experience fatigue problems. These models are efficiently analyzed through FORM/SORM techniques (first- and second-order reliability methods). A simple, analytical g-function (limit state) is established, which may be directly incorporated into standard FORM/SORM software packages. We describe here one such code, which includes a 14-variable formulation, its capabilities, input parameters, and output. Results are shown from this code, including parametric sensitivity studies across distribution parameters, types, and target fatigue lives.