Li Dongya, Jiang Wanchao, Xing Qingqing, Liu Qingsheng
Applied Technology College of Soochow University, Suzhou 215000, China.
School of Mechanical and Electric Engineering, Soochow University, Suzhou 215131, China.
Materials (Basel). 2024 May 11;17(10):2286. doi: 10.3390/ma17102286.
Unbonded flexible risers consist of several helical and cylindrical layers, which can undergo large bending deformation and can be installed to different configurations to adapt to harsh marine environments, and is a key equipment in transporting oil and gas resources from Ultra Deep Waters (UDWs) to offshore platforms. The helical interlayer of an unbonded flexible riser makes the structural behavior difficult to predict. In this paper, the axial tensile behavior and the axial tensile ultimate strength of an unbonded flexible riser are studied based on a typical 2.5-inch eight-layer unbonded flexible riser model, and verified through a theoretical method considering the contact between adjacent layers. First, the balance equation of separate layers is deduced by a functional principle, and then the overall theoretical model of an unbonded flexible riser is established considering the geometric relationship between adjacent layers. Then, the numerical model considering the detailed geometric properties of an unbonded flexible riser is established to simulate the axial tensile behavior. Finally, after being verified through the experimental results, the axial tensile stiffness and axial tensile strength of an unboned flexible riser considering the elasticity of the tensile armor layer are studied using the proposed two methods. Additionally, the effect of frictional coefficients is conducted. The numerical and theoretical results show good agreement with the test results, and the friction between adjacent layers would increase the axial tensile stiffness of an unbonded flexible riser.
无粘结柔性立管由多个螺旋层和圆柱层组成，能够承受较大的弯曲变形，并可安装成不同的构型以适应恶劣的海洋环境，是将超深水（UDW）中的油气资源输送到海上平台的关键设备。无粘结柔性立管的螺旋夹层使得其结构行为难以预测。本文基于一个典型的2.5英寸八层无粘结柔性立管模型，研究了无粘结柔性立管的轴向拉伸行为和轴向拉伸极限强度，并通过考虑相邻层间接触的理论方法进行了验证。首先，通过泛函原理推导了各层的平衡方程，然后考虑相邻层间的几何关系建立了无粘结柔性立管的整体理论模型。接着，建立了考虑无粘结柔性立管详细几何特性的数值模型来模拟轴向拉伸行为。最后，在通过实验结果验证后，利用所提出的两种方法研究了考虑抗拉铠装层弹性的无粘结柔性立管的轴向拉伸刚度和轴向拉伸强度。此外，还研究了摩擦系数的影响。数值和理论结果与试验结果吻合良好，相邻层间的摩擦会增加无粘结柔性立管的轴向拉伸刚度。
