Precision bending of thin-walled tubes based on inserted magnetic rheological particles as infill

A method for improving the bending accuracy of thin-walled tubes with hard ferromagnetic particles as inner filling was proposed, utilizing the magnetorheological property under magnetic field to provide support to the wall. Physical experiments and numerical simulations of rotary bending of 304 stainless steel tubes, with outer diameter of 12 mm and thickness of 0.5 mm, were carried out. Results show that using magnetorheological ferromagnetic-particle filling can effectively control the distortion of cross section, wrinkles and other defects of tube wall during bending. The section ellipticity within the deformation zone decreases by 71% after the infill was added, and the ellipticity decreases when the magnetic field applied enhances, reaching a maximum drop of 88%. Additionally, the filling reduces the wrinkling degree of inner wall of tubes. The wall thickness distribution within the curved deformation zone is more uniform, and the maximum wall thickness decreases from 0.68 to 0.54 mm, meanwhile the minimum wall thickness also increases slightly. © 2018, Editorial Board of Journal of Huazhong University of Science and Technology. All right reserved.