| With the depth of oil and gas exploitation in subsea constantly increasing, the demand for the equipment which is used in subsea production system has been more and more stringent. Umbilical cable is one of the important equipment in underwater production system which is introduced to connect the top floating body and the bottom production system, providing electric power, optical signal, hydraulic pressure, chemicals for the underwater production. Umbilical cable is typically unbonded composite structure made of optical fiber, electric cable, steel tube, and all of those helical components. During the installation, storage, transportation and operation umbilical cables will suffer the impact of functional and environmental load, which cause complicated nonlinear phenomenon such as contact, friction, extrusion and so on. At the same time, the power transmission of umbilical cable will produce a lot of heat, which cause the sectional temperature rise up, and the impact on the mechanics performance of material and even whole structure of umbilical. Therefore, in the operation umbilical cables don’t only suffer complicated ocean environment loads but also impact of other physical fields which cause intercoupling effect of multidisciplinary between each other makes design and analysis for umbilical cables more difficult. Since the deep-water oil and gas exploitation started relatively late in our country, the industrial production equipment is still in the initial stage without the capacity of design and production about umbilical cables independently. So our country has to depend on import from foreign umbilical cables, which slows down the speed of oil and gas exploitation.Firstly, in this paper a detailed investigation is systematically performed for the design and analysis of umbilical cable in the world. Relevant failure modes of umbilical cable under the function loads are analyzed, which provide corresponding design and analysis methods for the key supporting components such as armor wires, filling bodies, hydraulic tubes. And, semi-numerical analysis methodology is presented to obtain the more execute capacity curve, because theoretical method has too much assumption. Secondly, with the consideration of effect of released heat on material and mechanical properties, theoretical method is modified to analyze the heat influence on sectional stiffness, and numerical models are established to obtain the temperature distribution under a certain transmission power. Meanwhile, coupling method is introduced to analyze radial mechanical property. It is found that influence of temperature on radial stiffness reach up to 83.1%. Finally, Based on the symmetry and compactedness principles mentioned in the specification of umbilical, corresponding quantitative indices are introduced and a preliminary theoretical design method is presented. During the power transmission multi-physical fields are involved and thermal effect is analyzed by the way of thermal and mechanical coupling method. Then, a simple optimization method is introduced and, the multidisciplinary optimization framework considering the mechanical properties and thermal field analysis of umbilical is established, and the program is crafted to get the multi-objective optimal solution set. Consequently, the optimal result is selected through engineering experience, which performs much better properties compared with the initial design. The efficiency and feasibility of the whole optimization design strategy is abundantly validated, which provides a significant guidance to the umbilical cable design.This research of the dissertation is sponsored by Hi-Tech Research and Development Program of China (863 Program,2014AA09A224-2-2)... |
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