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

Abstract

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.

Numerical Calculation of Stresses in Helical Cable Elements subject to Cable Bending and Twisting

“…This means that if the cable element initially follows a thin, helical curve painted on the beneath cable sheath, the cable element will cover the painted curve also after cable bending. , , and Tjahjanto et al (2017) present results from physical tests and finite element simulations which conclude that this assumption holds. …”

“…Several papers have been published on this topic, for example Tjahjanto et al (2017), which present interesting results on fatigue stresses of helical power phases in a three-phases power cable based on finite element simulations.…”

Characterization of the Mechanical Properties of Low Stiffness Marine Power Cables through Tension, Bending, Torsion, and Fatigue Testing

“…These armor layers increase the axial, bending, and torsion stiffnesses of the cable's cross-section. Figure 1 shows a traditional dynamic marine power cable from [31], wherein the authors numerically studied the cable's mechanical behavior through 3D finite element simulations in which the cable was subjected to combined axial tension, radial pressure, and bending load conditions.…”

Experimental and Theoretical Study on the Prediction of Axial Stiffness of Subsea Power Cables

“…6). The values of the physical properties of yarn and armor wires required for theoretical analysis were obtained from Tjahjanto et al (2017). In addition, the average elastic modulus of 36,500 MPa and Poisson's ratio of 0.4 were applied for the simplified core considering the elastic modulus of each layer and ratio of the cross-sectional area.…”

“…For example, the following are software programs specialized for the mechanical analysis of pipes and cables with composite hierarchical structures, such as subsea power cables: CableCAD; Helica; UFLEX; and commercial software based on the FEM, such as ABAQUS, COMSOL, and ANSYS. Shaw (2011), Lu et al (2017), Tjahjanto et al (2017, and Chang and Chen (2019) investigated the behavior of subsea cables by performing 3D finite element analysis. In addition, they compared the results of the numerical analysis with theoretical formulas or experimental results.…”