Effects of Applying Axial Tension in the Rotary Draw-Bending
Process of Extruded Square Tubes

Abstract

The use of extruded aluminum alloy sections is advantageous for reducing the weight of many types of structure. In general, a secondary forming process such as bending is required when these materials are applied on structural members. However, in the bending process, undesirable deformation such as flattening and wrinkling arise easily. In this study, an improved rotary bending process is used for fabricating light gauge square tubes of A6061S and 63S-O. Flattening distortion on the cross section is restrained using an elastic laminated mandrel. In this study, we show that applying optimum axial tension is effective for suppressing wrinkling in order to reduce compression strain. For example, bend degree reaches 4.3 at the minimum R₀/H₀ without any defects, under the working conditions using a thickness ratio of A6061S and 63S-O tubes of t₀/H₀=0.038, where R₀, H₀ and t₀ are the radius of the central plane, and the height and thickness of the square tube, respectively. Moreover, applying axial tension is effective for increasing the working limit, especially for thin-walled tubes, because in the thickness ratio of A6063S-O of t₀/H₀=0.025 the working limit is 10.3-fold that under non axial tension.