Evaluation of deformations in corrosion thin walled pipes at cold bending with rolling

Corrosion-resistant thinwalled pipes are widely applied in aviation, rocket engineering, space engineering, ship building, mechanical engineering, iron&steel and non-ferrous industry, atomic energy, chemical, oil and gas industries and other areas. Pipe bending is one of the key operations of the technological procedure for pipeline part manufacture. Despite this fact, under modern production conditions it is virtually impossible to perform high-quality bending in the cold condition of pipes having the diameters larger than 60-70 mm as it is followed by the phenomena which are undesirable for the further operation: wall thinning on the pipe external side, elongation (flattening) of a cross-section, corrugation and fracture occurrence on the inside of a pipe. The technology for thinwalled pipe bending developed by SUSU eliminates the above-mentioned drawbacks. At the rotation of a burnisher put into a pipe with quite a hard pull, at each point of a rolling annular area an alternating bending occurs when bending stresses reach the yield stress for a short time. Thus, at the application of a relatively small bending strain a moving rolling annular area bends. The article considers the results of the experimental evaluation of deformations in thinwalled pipes at bending with rolling. The authors provide the procedure for the experiment conduct. To conduct experiments, they used a special machine for pipe cold bending with rolling. The method of deformation evaluation is based on the “Net method”. The authors determined the elongation and shortening values for pipe walls involved in bending. The conducted research allowed for the evaluation of the deformation extent and nature in longitudinal and transverse sections of the pipe walls at bending with rolling and, as a result, the authors managed to calculate the specified deformations and pipe wall thinning which is an important operation characteristics.