Effect of contact states in the tube on the push bending with low-melting-point alloy as filling medium

The cold push forming method of 1D bending radius (R/D = 1) with small diameter and small bending radius using low-melting-point alloy as filling medium is studied in this paper. The contact states between the outer surface of the filling medium and the inner surface of the tube are proposed to adjust the material flow of the tube blank. Based on ABAQUS/Explicit, simulation methods were used to investigate the effects of the contact modes on the quality of the elbow in four parameters. Experiments were carried out to verify the reliability of the simulations. The results show that the 5A02 thin-walled aluminum alloy tube, of which the diameter D is 12 mm, the thickness t is 1 mm, and the bending radius R is 12 mm, can be successfully fabricated by push bending using low-melting-point alloy as filling medium. The extended length of straight segment increases with the increase of the friction coefficient in the tube, but decreases with that of the outer surface of the tube. And the friction coefficient on the compression side of the medium affects more on the extended length than that on the tensile side. Differential contact modes used to the inner surface of the tube can improve the thickening and thinning of the elbow than uniform contact. The optimal elbow was obtained under the contact Mode 7, when the friction coefficient on the compression side was 0.06 and that on the tensile side was 0.01.