EXPERIMENTAL AND NUMERICAL INVESTIGATIONS OF A LEAD ALLOY USED IN SUBSEA POWER CABLE

Abstract

Subsea Power Cable are used to carry electric power in marine environment, where are commonly installed on the seabed. The internal conductor is wrapped by electric insulation and several protective layers, among these a lead sheathing insulates the conductor from sea water. The characterization of the lead alloy with respect to load condition is a challenging procedure, that involve several experimental efforts. Testing procedure is complicated by the high ductility of the material along with time dependent deformation at room temperature. Digital Image Correlation has been used during the test for numerically reconstruct the strain pattern on the specimen s surface and avoid errors due to the deformation induced by the clamping system. Several models have been proposed in literature for predict the response of material that undergo creep deformations. The development of power generation and aviation industry has made extensive effort in the characterisation of creep-fatigue behaviour of steels in the high temperature range. On the other hand, extensively research has been made for predict creep-fatigue life of solder joints used in microelectronic industry. Most of the models developed in the past years are already implemented in commercial Finite Element Code such as Abaqus or Ansys. In the present work is provide an overview of the creep mechanism and numerical model that are used for replicate creep response. considering the reliability of the approach and comparing the result of different models. Then the lead alloy actually used in SPC is investigated trough tensile, relaxation and cyclic tests. The test campaign is performed on three different specimen s geometries, having different thickness in order to investigate the influence of thickness on alloy s response. Stress-strain plot, obtained through tensile tests with different imposed value of strain rate are used, in conjunction with relaxation and cyclic tests to develop numerical model, focus on finite element approach and its implementation into commercial code. Purpose of the last part of the project is investigate the fatigue life of the material and provide an overview of the failure mechanism, analysing the dependence with frequency and strain range.