Study On Rigidity Influence Law Of Over-bending Setting Round For Pipe End Of Large Welded Pipe

After be used a period of time, large straight seam welded pipe can be lead to oil andgas pipeline leakage due to butt weld and other causes of failure. In order to avoid theleakage accident, this need to improve the quality of the weld and corrected the geometryof large stright seam weled pipe end. At present, enterprises use the process ofover-bending setting round for pipe end to change the geometry of welded pipe end part.But the enterprises set round, they mainly rely on the operator’s experience, and it isseldom that scholars both at home and abroad do the research of over-bending settinground, therefore, their influence rule need be studied when pipe end department be settedround.Over-bending setting round process can be divided into the external pressure andinternal expanding, this article uses over-bending setting round process of the externalpressure type and establish axisymmetric model using bilinear hardening material model.Through the analysis of the stress and strain distribution, the local deformationcharacteristics, cross section shape and simulated data in circle flat correction model andflat circular correction model, the conclusion is circle flat correction model is equivalent toflat circular correction model.Using circular flattening model, this paper studies the influence law on rigidityaccording to the laws of the tube billet after unloading elastic recovery. Do the simulationin this paper the diameter of the pipe is Φ76.2mm, by changing the tube billet’s maindeformation zone length, thickness and radius of die, the artical study the influence law onrigidity. Do the experiment, with Φ76x4mm tube billet testing, the artical validates thevalidity of the law when the deformation zone length of the pipe billet are different. Therules in the actual production provides a theoretical guidance for bending of corneringcircular correction.In the last this article does the research of mould parameters’influence law on thepipe wall thickness changes to provide reasonable determination of die radius, thestructure and shape parameter of the end of die the basis.