Modeling Research And Experiment Of Rigid-flexible Coupling Straightening Process For Thin-walled Pipes

In the process of pipe processing,straightening is an important process to ensure that the workpiece meets the straightness requirements.The commonly used reverse bending straightening is to control the straightness by applying a reverse load to the bending part of the workpiece to generate elastic-plastic deformation.a method.Section flattening and distortion of thin-walled pipes are common phenomena in the straightening process.In order to solve this phenomenon,this paper takes thin-walled pipes as the research object,and by analyzing the stress-strain relationship in the section flattening area during the straightening process,it is obtained that one of the factors affecting the section flattening is the elastic zone ratio.Taking advantage of this factor,a pressure correction mechanism composed of superelastic materials is used to analyze the deformation of the flexible part,and the deformation of the flexible body part of the pressure correction mechanism and the straightening stroke of the pipe are coupled to establish rigid-flexible coupling straightening of thin-walled pipes.The mathematical model of the straightening process is verified by the simulation and experiment of the straightening process.The main content and work are as follows:(1)Based on the elastic-plastic theory and the Brazier effect,analyze the stressstrain relationship in the flattening area of the section,consider the strengthening behavior of the material,establish the constitutive relationship of the flattening deformation area of the thin-walled pipe section,and further deduce the relationship between the flattening amount of the section.By analyzing the relationship of the flattening amount,it can be known that one of the factors affecting the flattening degree of the pipe is the elastic area ratio.(2)In view of the flattening phenomenon of the section during pipe straightening,the pressure correction mechanism is designed,the Mooney-Rivlin rubber constitutive model is used to analyze the deformation of the flexible body of the pressure correction mechanism,and the deformation is coupled with the stroke during pipe straightening.A new straightening stroke deflection model is established to predict the straightening stroke of the pipe and theoretically calculate the section flattening amount.(3)Use finite element analysis software to simulate and analyze the straightening model and compare it with the results obtained from theoretical calculations.The research shows that the flattening of the pipe will also occur after the use of the rectifying flexible mechanism,but the amount of flattening of the cross-section is smaller than that when the rigid indenter is used.(4)Conduct straightening experiments on thin-walled pipes,and compare the experimental results with simulation and theoretical data.The results show that the flattening phenomenon of the section is improved after the straightening is completed,and the data obtained from the experiment and the theoretical and simulation data are all within the allowable error range.