Numerical Analysis For The Typical Multi-point Bending Process Of Aluminum Alloy Profile

Aluminum alloy profile is a kind of structural material with lightweight quality, highstrength, excellent conductivity and smooth shape. As an ideal material for the lightweightconstruction design, aluminum alloy profile is widely used in the production of automobile,spacecraft and skyscraper. Considering aerodynamics, structural mechanics, artistic style andsome other factors, profile generally needs to be bent into certain curvature. Multi-pointforming (MPF) technique is a new kind of flexible forming method for3-D surface and hasbeen successfully applied to form plate parts but not for profiles. Combining MPF intobending process has significance for improving the forming effect of profile and expandingproduct line.In this paper, several typical MPF processes were applied to bend aluminum alloyprofiles and the reasonable forming condition was established. The main research contentand conclusion are as follows:1. The finite element model of multi-point bending process of A6N01S-T5aluminumalloy profile was established, including constitutive equations, meshing parts withappropriate elements, bringing symmetric constraints and loads. The tensile experiment wasconducted for the profile property and plastic stress-strain relationship.2. In the multi-point bending process for profile, dimples and cross section distortionoften occur and also can be restrained by appropriate forming measure. The punch elementsize with15mm×15mm and spring steel plate with thickness3mm can restrain the dimpleseffectively. The inner pressure estimated by specified equation in the cavity of profile can restrain the cross section distortion.3. Both solid die and Multi-Point die were used for bending profiles into different radii.The forming effects of these two techniques indicate that MPF can be used for profilebending especially when the bending radius is larger than2000mm.4. The profile bending process with multi-step MPF was simulated and analyzed.Forming path and forming times are the key factors influencing the forming effects. Theforming effect with curvature uniform path is better than that with radius uniform path. Themore times profile is bent, the better the forming effect will be but with forming harden. Theprofile was bent by both single step MPF and multi-step MPF and the contour line after bent,the stress distribution on the profile surface and cross section distortion were compared. Theforming effects indicate that multi-step MPF can be used for bending profile with smallerradius.5. The profile bending process with sectional MPF was researched. The transitionforming region between formed and unformed region was designed by NURBS theory forcoordinating the shape difference. The transition forming region can restrain the formingdefects effectively and the larger the transition forming region is, the better the formingquality will be. Compared with the profile bent by single step MPF, the one by sectionalMPF is more closed to object shape with less cross section distortion, which indicates thatsectional MPF is reasonable for profile bending.