APPLICATION OF NUMERICAL-SIMULATION IN THE BENDING OF ALUMINUM-ALLOY PROFILES

This paper deals with 3D elasto-plastic finite-element analyses of the production bending of aluminium extrusions. The overall objective of the study is to determine the applicability of using the general purpo se software MARC K5.2 in analysing industrial rotary draw bending and stretch bending. The main focus is placed on the effects of material b ehaviour, slenderness of cross-sectional members, and die geometry on geometrical tolerances. The influence of applying external pre-stretch ing and internal support for obtaining better tolerances is demonstrat ed also, The results have been validated by a number of tests carried out in the laboratory and using industrial bending machines. The resul ts show that wrinkles and sagging, or 'suck-in' of the flanges, can be eliminated by applying a stationary internal mandrel in combination w ith an infernal web, even with tight radii. Furthermore, external pre- stretching is shown to be advantageous in order to reduce local buckli ng and spring-back. It has been found that the thickness variation exp ected after extrusion is of the same importance as anisotropy with res pect to sagging in stretch bending. Elastic spring-back is influenced by the strain-hardening characteristic and the amount of axial loading applied, both decreased strain hardening and increased tension ensuri ng reduced spring-back. The experimental and numerical results appear to be in excellent agreement, indicating that extrapolation of the res ults to cases? other than those tested, may be possible. It is conclud ed that finite-element analysis has proven to be a well-suited numeric al tool for design and product optimisation in industrial bending.