Effect of applying a laminated elastic mandrel to the draw bending process of extruded square tubes

Extruded aluminum alloy sections are advanced materials in use as lightweight structural members. A secondly forming process such as bending is required when these materials are used for structural members of automobiles. It is known that undesirable deformations as wrinkling and split tend to occur easily when some sections having light gauge are formed by the bending process. This report shows the working limit for the draw bending process of square tubes with a laminated elastic mandrel. A6063S and A6061S square tubes having various thickness are applied to this experiment. It is shown that applying laminated elastic mandrels to this draw bending process is very effective in preventing either primary distortion or wrinkling of compression flange and compressive region of webs. In consequence, higher working limit is obtained by this method. On the working conditions of the thickness ratio t0/H0=0.075 or 0.05 of A6063S–O and A6061S–O, the working degree R0/H0 reaches to 2.4 or 4.3 without any defects, where t0 and H0 mean thickness and the height of the tube respectively.