Bending Mechanics of Cable Cores and Fillers in a Dynamic Submarine Cable

Dynamic submarine cables are used to provide electrical power to floating oil/gas production platforms and to export power from marine renewable energy systems such as floating wind turbines. During installation and life-time operation, the dynamic power cable is subjected to various loads, e.g. axial tension, bending and torsion. A typical three-phase AC cable consist of three helically-interwound power cores with three polymeric fillers to accomplish a circular circumference over which sheaths and tensile armour layers are applied. The present paper focuses on the mechanical behaviour of a dynamic submarine cable subjected to a combined axial tension, radial pressure and bending load. Particular interest is emphasized on the stick-slip behaviour of the helically-interwound power cores. 3D finite element (FE) model has been developed, where the interactions on all layers of the cable are extrinsically taken into account. The stick-slip behaviour of the power cores and the resulting friction stress induced during cable bending can have a large impact on the fatigue life of the dynamic cable. Kinematics of slips between the cable core components resulting from FE simulations will be analyzed and compared to the assumption of fully loxodromic slips typically used in the formulation of analytical model for helically-wound cables. The output of the present analyses will provide a better understanding on the mechanical behaviour of the power cores of dynamic submarine power cables in response to cable bending and provide a basis to verify and develop analytical models that can be used for, e.g. fatigue life assessments.