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Cycles: Fatigue Reliability Formulation and Analysis

Report No. : 
C.H. Lange
S.R. Winterstein
April 1994
RMS13.pdf6.35 MB

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 of 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.