Numerical Simulation And Performance Study Of The Cold Bending Process Of X90 Line Pipe

As a kind of special equipment for oil and gas transportation, cold bending pipe is widely used in oil and natural gas pipeline project, whose main role is to change pipeline route with a small angle to meet the construction requirements of complex terrain area. With increasing of the diameter and the steel grade of long-distance pipeline, the difficulty of producing cold bending pipe increases. If production of cold bending pipe is not well controlled, it will cause a negative impact on the fatigue performance, carrying capacity and safety of service, so as to increase the risk of the failure of the cold bending pipe. Therefore, it is very important for the production of cold bending pipe with high-quality and high-performance to optimize the parameters of cold bending process in the actual production process. In this paper, numerical simulation is used to simulate the molding process of cold bending pipe. The main works of this paper are as follows:(1) Study on molding process of cold bending pipe:the forming mechanism of cold bending pipe, the stress analysis of bending section and the analysis of potential quality defects in bending process.(2) Numerical simulation analysis for molding process of cold bending pipe. According to the actual situation of the field, the finite element model of cold bending pipe is established, including material parameter setting, unit selection, meshing, contact and boundary conditions. Then, the finite element analysis of the first cold bending process is carried out, and stress and strain distribution is obtained. Finally, subsequent bending finite element analysis is carried out. The bending angle of each step and the whole bending angle is calculated.(3)Dimension analysis of cold bending pipe:the rebound quantity, the ellipse degree, the wave degree as well as the wall thickness reduction rate size. Dimension of cold bending pipe should be within specified range, and meet acceptance criteria of cold bending pipe.(4) Analysis and calculation of blasting pressure of cold bending pipe. By numerical simulation analysis, the blasting pressure of cold bending pipe is obtained. At the same time, the blasting pressure of straight pipe is calculated as a reference. The results show that the load carrying capacity of cold bend pipe is less than that of straight pipe, which indicates that the cold bending process weaken the carrying capacity of the pipe.(5) Optimize the process parameters (cold bending step, the angle in each step) of cold bending pipe by analyzing the influence of molding process parameters on the dimensions of cold bending pipe.