Defining Local Stress-Strain Fields in Ductile Components under Cyclic Loading
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Subsea power cables consist of an extruded lead alloy sheathing, which act as a protective layer against water penetration. The lack of research and framework for advanced fatigue calculations of lead has made it difficult to estimate fatigue lifetime of the lead sheathing. The present-day design is based on operational track records with excessive design margins. The purpose of this thesis is to contribute with a methodology framework which can later be used to describe the fatigue life of lead sheathing. This study focused on comparing the stress - strain field from experimental and numerical testing. The investigated specimen thickness was 1.8 mm. Tensile test configuration on 3D finite element modelling and mechanical testing with digital image correlation analysis was used. Two tensile test specimen geometries have been tested, the curved as a benchmark model, and the dogbone as a validation of the results. The strain rates investigated are [0.8E-7,0.8E-3] [1/s] for curved model and 1E-7 [1/s] ,1E-5 s [1/s] ,1E-4 [1/s] ,1E-3 [1/s] for the dogbone model. The Anand numerical material model produced a satisfactory fit with the experimental results. The curved tensile specimen geometry results had erratic results and a poorer fit with the numerical results, while the dogbone specimen geometry results were consistent and gave a good correlation with the numerical results. In future work it is important to treat the laboratory specimen carefully in the production, machining and when preparing the specimen for experimental testing. Another remark is to perform fatigue testing, both experimental and with the use of the finite element simulation.