Countermeasures against undesirable phenomena in the draw-bending process for extruded square tubes

Undesirable phenomena can easily occur in the process of bending thin extruded tubes. These phenomena include flattening distortions, wrinkling, folding, necking and splitting. Flattening distortion can be restrained principally by applying a mandrel. Wrinkling and folding can be restrained by additional axial tension. Splitting can be restrained by the use of a square tube with a center rib. These can improve the working limits in the draw-bending process for extruded aluminum square tubes. For a square tube (A6063S-O, H0/t0=20.0), a bend degree (H0/R0) of 0.42 was reached without any defects. For a square tube with a center rib (A6063S-O, H0/t0=20.0), a bend degree (H0/R0) of 0.57 was reached without any defects. To further analyze the draw-bending process, simulations were carried out using the finite element method (FEM).