Numerical Simulation And Theoretical Study On Small Radius Pipe Bending Through Medium Frequency Induced Temperature

With the growing demands of big radius pipes in ships,the traditional bending methods are too complexed and cost too much.Besides,the forming quality is not easy to guarantee.As with the bending of big radius pipes,the hot bending method is always the priority among all the ways.The method of pipe bending through medium frequency induced temperature is one craft of hot bending.Compared with the traditional bending ways,this method is easier to carry out and costs much less;what's more,the bending forming quality is relatively better.However,as with cold bending,hot bending pipe forming quality is directly related to the bending radius.The bending forming quality is relatively easy to ensure that if the bending radius is less than three times the diameter of the tube.But if the bending radius is greater than three times the diameter,the thinning rate and flatness will increase dramatically.In order to ensure the function and the safety of the structure,the "China Shipbuilding Quality Standard" stipulates the wrinkle and thinning rate and the flatness of the formed pipe.For the purpose of controlling the cross-sectional distortion and obtaining the better bending parameters,the research on the hot bending of small radius pipes is needed.The sequential coupling method based on certain means of acceleration is used to simulate the intermediate frequency hot bending process,and the reliability of the method is verified based on the comparison between the experimental results and the simulation results.In order to carry out the batch analysis of the pipe fittings and make it easier to get through of pre-process and post-process,this article also secondarily developed the Abaqus software based on Python language,providing the good graphical user interface for the user to carry out the intermediate frequency hot bending simulation.This secondary development of Abaqus is to achieve the goal of parameterized modeling and automatic post-process,which greatly accelerates the analysis of progress and improves the efficiency and provides support of the discussion on forming laws and the validation of the latter theoretical formulas.In order to investigate the influencing factors of the forming quality of the section,the relative position of the induction coil and the center of rotation,the propulsion speed of the pipe,the temperature and width of the heating temperature and the bending moment are analyzed and the forming rule is obtained.Based on some assumptions,the nondimensional inverse bending moment correction term is introduced under the original formula and the theoretical formula of the thinning rate under the influence of the anti-bending moment is deduced.The numerical simulation results of the pipe with different diameters and thickness are compared with the theoretical results.In the end,the theoretical formula is validated.