Theoretical analysis of over-bending straightening process with large diameter pipes

In fact,the over-bend straightening process for pipes straightening is three-point bending elastic-plastic deformation for small curvature curved beam.The problem of straightening curved pipes can be solved by studying the process of pure bending for straight pipes based on the pure bending equivalent principle for over-bend straightening.The bending process can be divided into the full-elastic deformation stage and the elastic-plastic deformation stage based on theoretical analysis of the process of symmetric three-point bending and springback for the straight pipes.The deformation zone of pipes in the latter stage can be divided into the elastic deformation zone and the elastic-plastic deformation zone.Based on the assumption of the tiny deforming theory,the computation models with these two stages are constructed.The equations for the rotation angle and bending deflection of each point in the neutral layer are derived for any given punch displacement.The theoretical analysis is verified by the experimental results.Both the theoretical and the experimental results show the linear relation between the punch displacement and the residual deflection of pipes,thus a convenient approach is provided to build the recognition model of springback law in the intelligent control system for over-bending straightening process.