Research On Fatigue Life Of Flexible Riser Bend Stiffeners Based On Monitoring Data

The bend stiffener device is installed at the connection between the flexible riser and the floating body to prevent excessive bending and fatigue damage accumulation of the flexible riser.However,facing the harsh marine environment,the fatigue damage of the bend stiffener is particularly prominent.Therefore,the monitoring of the movement status of bend stiffener is carried out,and the fatigue life assessment is carried out accordingly.It is of great significance to the safe operation of China’s deep-sea oil and gas fields and marine environmental protection.Based on the motion monitoring data of the flexible riser bend stiffener,this article will carry out the fatigue life analysis and research of the bend stiffener.The main research work is as follows:(1)Processing of motion monitoring data for flexible riser bend stiffenerThe quaternion method is used to update the instantaneous motion attitude angle of the bend stiffener,solving quaternion differential equations using fourth-order Runge-Kutta method,the coordinate transformation matrix and the quaternion rotation matrix are used to solve the instantaneous attitude angle,and the gravity acceleration is eliminated To get the motion acceleration.Then,using MATLAB software,the displacement of the monitoring point in three directions is calculated in the frequency domain by FFT.(2)Analysis of mechanical properties of flexible riser bend stiffenerUnder the action of load,the flexible riser bend stiffener will have large deformation and contact nonlinearity problems.To this end,using ABAQUS finite element software,considering the large deformation and nonlinear contact,a mechanical model of the flexible riser bend stiffener is established,and the dangerous section stress distribution is calculated by inputting the processed monitoring displacement load data.(3)Fatigue life analysis of flexible riser bend stiffenersThrough the stress distribution of the dangerous section of the bend stiffener,combined with the stress-strain tensile test curve of the polyurethane material,the stress-strain analytical formula of the bend stiffener was fitted by a fourth-order polynomial to obtain the equivalent stress distribution of the dangerous section.Combined with the results of the ε-N fatigue test curve of the bend stiffener material,the fatigue life of the dangerous section is calculated.