A novel differential lubrication method for push-bending of L-shaped thin-walled tube with 1D bending radius

A novel differential lubrication method is proposed to improve the deformation behavior of L-shaped thin-walled with relative bending radius of 1 in push-bending process. The optimized tube blank is divided into four zones: inner deformation zone, inner guide zone, outer deformation zone and outer guide zone, which are lubricated with different lubricants. The differential lubrication and uniform lubrication methods for tube push-bending are first explored by means of simulation and experiments. The simulation results show that the differential lubrication method is more effective than the uniform lubrication method in suppressing wrinkles and expanding the process window. The outer thickness of tube increases with the increase of friction coefficient of the outer guide zone and the outer deformation zone, while the extension of tube end decreases with the increase of friction coefficient in any zone. Furthermore, with the proposed differential lubrication method, L-shpaed push-bending experiments of 5A02 aluminum alloy and 1Cr18Ni9 tube with relative bending radius of 1 were carried out to investigate this effect. The experimental results showed that the differential lubrication method effectively avoided wrinkling and the experimental results agreed well with the simulation results in wall thickness distribution and the extension of tube end.