Numerical Simulation Of Mechanical Behavior Between Composite Marine Riser Layers

The development of society requires people to search for energy through various means.The ocean bigger than the land is gathering more and more people's attention.Therefore,energy development in the deep sea has become an important issue in contemporary society.Marine risers,as the most important porters of energy,have never left the field of concern.As people explore the depth of the ocean,the current traditional metal composite pipe shows some incompatibility.The application of composite materials makes the pipeline show more superiority.Therefore,it is very meaningful that research on new composite pipe risers can improve our deep sea exploration ability.From the point of view of the application of new materials and improvement of performance in marine risers,this paper aims to reduce the weight of pipes,and replaces the structural layers of some metal materials in traditional risers with carbon fiber composite materials to form steel-carbon fiber double-frame structure risers.At the beginning,in order to explore the excellent applicability of carbon fiber materials,three models of pipes(metal pipes,steel-carbon fiber material pipes,carbon fiber composite pipes)were established,and the mechanical properties of the three pipes under sea conditions were analyzed,and their advantages and disadvantages were compared.Analyze which material's riser is more suitable for use as a riser.Then establish a steel-carbon fiber double skeleton riser model,carry out basic bearing analysis of the main functional structural layers,verify the rationality of the structure,and explore the boundary conditions,carbon fiber tensile layer angle,interlayer friction coefficient,internal and external pressure and other factors on the influence of the axisymmetric properties and bending properties of the steel-carbon fiber riser.After the stiffness analysis is completed,the linear surface pressure stability analysis of the double-frame riser includes the effects of riser length,carbon fiber tensile layer angle,and interlayer friction coefficient on the radial stability.Then,for the actual situation,a nonlinear radial stability analysis introducing initial defects(initial displacement and ellipticity)is performed.Through the analysis of this paper,it is found that the steel-carbon fiber structure pipeline has the best comprehensive performance among the three pipelines,and is suitable for use as a riser.When the steel-carbon fiber double skeleton model riser is stretched and twisted,the load is mainly from the metal.The skeleton layer and the carbon fiber tensile layer bear the load mainly by the two skeleton layers and a part of the carbon fiber tensile layer when subjected to internal and external pressure.Overall,the friction and boundary conditions of the structural layer have little effect on the tensile and torsional resistance of the riser.The external pressure is not conducive to the tensile resistance of the riser,which is good for torsion resistance,and the internal pressure is reversed.When the angle of the carbon fiber tensile layer is changed to the axial direction,the tensile strength is favorable,and the angle of the tensile layer of the carbon fiber of the riser is 50.It is most conducive to anti-rotation.The riser layer becomes "sticky",and the internal and external pressure is increased.The angle of the carbon fiber tensile layer is axially inclined,which causes the bending nonlinearity to be pushed back and also reduces its flexibility.The circumferential angle variation of the carbon fiber tensile layer and the rise of the riser are not conducive to the radial stability of the pipe.The presence of initial ellipticity and displacement,resulting in a large loss of yield resistance,can make the riser face very unstable.