Simulation of Behavior of Fatigue Cracks: A Complete Industrial Process on a Ship Deck Beam

To assess ship and FPSO condition, it is necessary to adjust the inspection process and the inspection planning efficiency in accordance with the safety target. Crack propagation may be a leading criterion for designing inspection planning particularly in high sea states. In order to realistically anticipate the possible propagation of either cracks not detected during inspection or cracks initiated after this inspection, a joint research project between three French companies (Giat Industries, CETIM, and Bureau Veritas) has been carried out to obtain an improved approach. This approach involves various steps of fatigue crack behavior leading to failure. This paper presents a part of this research dedicated to the development of tools applicable to ship and FPSO structural assessment. This method takes into account analysis of simultaneous cracks propagation. This technique avoids successive re-meshing all along the crack path. Multi-crack initiations and a Line Spring Method have been used to calculate the stress intensity factors, with a view to determining the crack propagation rate. An example is provided for a deck beam on a FPSO showing a significant gain in the fatigue life span prediction compared with current fracture mechanics analysis. This gain is mainly due to a better interaction analysis between local cracked areas and overall structural behavior