A New Fully Detailed Finite Element Model of Wire Rope for Fatigue Life Estimate of a Mooring Line

• Main Authors: Bussolati, Federico, Guiton, Martin L.E., Guidault, Pierre-Alain, Poirette, Yann, Martinez, Michael, Allix, Olivier
• Other Authors: Laboratoire de Mécanique et Technologie (LMT), École normale supérieure - Cachan (ENS Cachan)-Centre National de la Recherche Scientifique (CNRS), IFP Energies nouvelles (IFPEN)
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2019
• Subjects: fretting fatigue; beam model; Spiral strand wire rope; frictional contact; [SPI.MECA.STRU]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Structural mechanics [physics.class-ph]; [SPI.MECA.MSMECA]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Materials and structures in mechanics [physics.class-ph]; [SPI.MECA]Engineering Sciences [physics]/Mechanics [physics.med-ph]; Arctic
• Online Access: https://hal.science/hal-02338054

International audience Spiral strand wire ropes are commonly used in the mooring system of offshore structures. When dealing with the fatigue limit state, engineers have to consider many different load cases, according to the variability of the environmental state. This usually prevents the use of any detailed numerical model of the mooring lines. In this paper, we propose a new method to evaluate with an affordable computational cost the detailed mechanical stress state in different parts of the wire ropes used for mooring a floating offshore wind turbine. We first compute tension and bending history in the mooring, with the hydrodynamic software Deeplines, assuming for simplification stationary aerodynamic loads on the floater. These time series are then accounted for in a novel Finite Element Model of the spiral strand, with small sliding among the wires. The obtained kinematics and stress state of the wires can then feed a fatigue law based on fretting fatigue, which has been experimentally evidenced to condition the fatigue life of spiral strand wire ropes. The potential of this method is illustrated with an application to a cylinder-like shape floater equipped with 3 pairs of catenary mooring lines. It is shown that bending and tension histories do not significantly depend on the wire rope bending stiffness.