Structural Design And Faitgue Analysis For Elastomer Of Deepwater Riser Flexjoint

With the accelerated pace of development of deep-water oil and gas resources,China is in urgent need to develop deep-water oil and gas equipment of its own independent intellectual property rights.Steel Catenary Riser(SCR)is one of the key equipment in development of deepwater resources.Its structure and working environment makes it challenging to design,manufacture,install and use.The flexible joint is a key component that connects the SCR and the floating platform,which significantly reduces the movement stress between the floating platform and the SCR and can be adapted to different type of connections.Developed countries possess mature flexible joint technology,while the domestic technology only stays in theoretical stage.To contribute to the development of deep-water oil and gas equipment and technology in China,in this paper,research on SCR flexible joints of 1000 m water depth is carried out,which contains the folloing sections:(1)Using the catenary equation to calculate the SCR static.The top tension and bending moment of the SCR are obtained,which provides the load condition for the design of the flexible joint.The finite element software ABAQUS is used to calculate the dynamics of SCR.The beam element is used to simulate the cyclic load of SCR and the AQUA module is used to load the condition of the wave and flow.The Tension and moment history curves of the SCR are obtained,and the load conditions are provided for the fatigue analysis of the flexible joint.(2)The stress-strain curve of the rubber material was obtained by carrying out the basic mechanical test of the rubber material.Based on this,the constitutive model of the rubber material is fitted,and the constitutive model of the different rubber materials is compared and analyzed.The optimal constitutive model is selected to provide the material parameters for the structural design of the flexible joint.(3)The structural design parameters of the elastomer are analyzed in detail,the angular stiffness of the elastomer and the shear strain equation are deduced.Based on the orthogonal test method,the design scheme of the elastic structure is obtained,and the finite element software ABAQUS is used to analyze the different design schemes,and then the optimal design scheme is chosen.(4)The kinetic analysis of the elastomer is carried out.Based on the energy method in fracture mechanics and the FCG test data,the S-N curve of the rubber material is obtained.FE-SAFE software is used to analyze the fatigue properties of elasticity,and the area with high elastic fatigue damage is spotted.