Global and local modeling for inter-wire fretting in multi-wire copper conductors

Submarine power cables (SPC) are vulnerable to fretting, wear, and fatigue due to the dynamic environment, particularly at end connectors and junctions or other discontinuities, such as seabed features. This paper presents a finite element methodology for global and local analysis of fretting between copper conductors in multi-strand cables. The salient inter-wire fretting variables, such as relative slip and contact pressure, almost impossible to measure experimentally, are identified here via the three-dimensional, global multi-wire model, which includes frictional contact and large deformation effects. Local 2D and 3D representative models, typical of laboratory-scale fretting test configurations, are adopted, with fretting boundary conditions derived from the global model fretting variables, for detailed micro-scale resolution of fretting contact. A critical-plane, multiaxial fretting-fatigue life methodology is implemented to quantify fretting-fatigue life. The effects of lay angle, contact size, wire diameter, friction, and slip are investigated. It is shown that, in general, increasing lay angle, contact size, wire diameter, and friction lead to reduced life. A key novel contribution of the paper is identification of the fretting fatigue relationships between representative local 2D (Hertzian) and 3D (crossed cylinder) modeling, via matching contact pressure, and global multi-wire contacts. A rationalization of the relative contact size effects associated with transverse- and longitudinal-type contacts in such applications is also presented.