Study Of Full Size And Large Deformation Submarine Pipeline Girth Weld Bending Performance

As the rapid development of the global economy and non-renewable energy consumption, the Marine oil and gas resources are constantly developing to the deep sea. As one of the main laying ways at the deepwater and ultra deepwater sea, reel- lay method has obvious advantages compared to other laying way, the development of reel- lay method is still in its infancy in our country, and the development is imminent. The reel- lay method withstand repeated large plastic deformation and the performance of the girth weld, the adverse effect caused by development of reel- lay method must firstly be solved by girth weld bend performance simulation and bend performance evaluation, etc.For the above problems, first of all, to test the girth weld of pipe and the bend performance, we need develop large-scale simulation test device for a full-size bend; Then we respectively simulated the process of the pipe bend pushing course size, the relation of the mother material and weld matching, pipeline constitutive relation of sigma epsilon n = Kεn strain intensity coefficient K and the plastic hardening exponent n, the diameter of pipeline, the ratio of diameter and thickness, the diameter of the bending head to effect the bending behavior through the finite element simulation; At last, we also respectively stimulated the stress and strain when the pipeline buckling, the pipe diameter, the ratio of diameter and thickness, the pressure of inside and outside of the pipe to simulate the buckling through the finite element simulation. The main results are obtained as follows:A simulation test device for large full-size bend are developed, the maximum strain can achieve 5%. Finite element analysis results show that the matching of welding is suitable for bending test, but the low and high match is not suitable for bending test; the increasing of forward distance, pipe diameter and the ratio of diameter and thickness will increase the stress and strain in the process of pipe bending increases; the increasing of strain intensity coefficient K, and the plastic hardening exponent n and the radius of bending head will decrease the stress and strain in the process of pipe bending. The results of the finite element simulation show that, under the parameters of a simulation test device, the relation between the critical buckling curvature radius and the diameter is Br = 2643.3 + 9.84×D, the relation between the diameter and buckling deformation is St = 0.006 + 3.84× 10-4 D; the ration between the buckling curvature radius and pipe wall thickness is Br = 12646-441.7 Th, buckling strain increases with the reduction of wall thickness. In addition, the simulation results show that when the bent pipe under external pressure conditions, local buckling occurred more often; And pipe under internal pressure when the condition of the buckling occurs, the local buckling of the concave size decreased, and bulge will appear. The results of finite element simulation can be used to provide guidance for the bend simulation test device for a full-size girth weld pipe bending test.