Research On The Model And Static Analysis Of Unbonded Flexible Risers

As the development of marine oil and gas exploration in deep sea,the unbonded flexible riser has been widely used.And it is the lifeline of offshore oil and gas exploitation.However,there are still some problems in the analysis of the mechanical properties in unbonded flexible riser now.The unbonded flexible riser is composed of cylindrical layer and spiral layer.The cylindrical lay is made of the polymer,and the spiral layer consists of steel strips wound at an angle.Therefore,there is separation and slippage between each layers.This behavior has a profound impact on the mechanical properties of the unbonded flexible riser.This paper summarizes the results of flexible riser at current research firstly.On this basis,the influence of torsion on various bearing capacities of flexible riser is discussed.The main work is divided into the following aspects:1)According to the structure and mechanical properties of the flexible risers,the theoretical model of unbonded flexible riser under axisymmetric load and bending load are established2)According to the structure and mechanical properties of the flexible risers,this paper established a detail model including the models about the details of Parcass layer and Pressure Armor.And a simplified models without those detail models.In order to avid the misconvergence in calculating,the ABAQUS/Explicit quasi-static method is used for calculation.According to the experimental results in references,the validity of the numerical model is verified.3)According to the theoretical model and numerical model for calculating the axisymmetric load of flexible riser proposed in this paper,the inconsistency of stiffness due to positive and negative torque and the effect of tensile stiffness due to torsional load are discussed according to the radial deformation of each layer.This paper also discussed the effect of torque on the stiffness of flexible riser.