Validation of naval vessel spectral fatigue analysis using full-scale measurements

Abstract

Full-scale measurements taken during a naval vessel sea trial are compared to calculated stress spectra and associated fatigue damage estimates using linear frequency-domain hydrodynamic and finite element analysis codes. Results were generated using four different wave spectrum models to better understand their influence on fatigue damage estimates. The results using measured two-dimensional wave spectra were most similar to measurements, but the agreement with measurements for each of the spectrum models was acceptable. Significant improvement in calculation accuracy was observed when adding a spreading function to longcrested wave spectra. The use of ±90° as the extent of wave spreading gave results with minimal differences from the use of measured spreading angles. The agreement between measurements and calculations using longcrested wave spectra with a constant spreading function is fortunate because available seaway data are commonly limited to wave height and period combinations. The results of this study suggest the spectral fatigue analysis method can be used to generate reasonable estimates of stress spectra and resulting fatigue damage for a naval vessel.