A feasible study of fatigue life prediction for marine structures based on crack propagation analysis

Abstract

Marine structures such as ships and offshore platforms are designed with damage tolerance. This requires accurate prediction of fatigue crack growth under service conditions. Current fatigue strength assessment methods for marine structures are largely based on the cumulative fatigue damage (CFD) theory using stress-endurance (S-N) curves. The effects of initial defects and the load sequence have been neglected. The extent of final fatigue failure in real structures is also not specified. These result in a large scatter of the predicted fatigue lives. In the fatigue community, more and more researchers have realized that fatigue crack propagation (FCP) theory could overcome these deficiencies and has the potential to explain various fatigue phenomena observed. In this paper, a feasible study of fatigue life prediction for marine structures based on FCP theory is carried out. The basic requirements and the general procedure for such an analysis are addressed. The feasibility of this procedure and the capabilities of FCP theory for fatigue life prediction are demonstrated using a simple example of a finite width plate with a centre crack subjected to remote uniform fatigue loading. The key problems to be solved for a practical implementation are also discussed.