Fatigue Internal Stresses And Deformations Of Electrical Umbilicals: Analytical Work

This paper reports the analytical part of a development project into the design and fatigue performance of composite umbilicals. A computer model of an all-electrical, symmetrical umbilical subjected to various axial loads and bent around sheaves of different diameters has been developed. Relative sliding between the cores and stresses due to bending and friction is calculated. UMBILICAL DATA turned out to be very successful. The analytical work, which will be presented in this paper, had to be based on several assumptions and unknown parameters. Some of these could be tested directly; others could only be tested indirectly by observing which assumptions and parameter values gave correspondence between calculation and test results. Fig. 1 shows the investigated umbilicals. The centre core and the three inner layers consist of polyethylene insulated copper conductors with a copper section area of 1.5 mm2. The conductor was solid, 7-stranded or multistranded. The number of cores in each of these inner layers was 6, 12 and 18, and the lay lengths 2. UMBiliCAL DATA