Fatigue damage analysis of dynamic power cables by laboratory testing and FE analysis

The study presents a comparison of models that can be used for fatigue life prediction of dynamic subsea power cables. It compares and discusses the modelling of fatigue damage degradation mechanisms that may be critical. Results from cyclic tension-bending laboratory tests were used to compare the numerical models and hypotheses on governing fatigue damage mechanisms. The BFLEX fine element software developed by SINTEF Ocean was used to model and simulate the laboratory tests. The model was developed based on the hypothesis that the conductor’s fatigue life is mainly governed by longitudinal stress ranges where the fatigue life can be predicted using SN-data for individual wires. The comparison of the results between the numerical simulations and tests showed that the numerical model overestimated the fatigue life. Hence, a model for fretting analysis between the wires was developed. The results from this model showed better agreement with the test results compared to the former model. It was concluded that the fatigue damage process of the conductors tested in the cyclic bending-tension tests was induced and governed by fretting, especially for small bending radii, with a clear superposition of damage caused by cyclic longitudinal stress ranges