Evolution of material properties and optimization of process parameters during hydroforming of aluminum extrusions

Tube hydroforming has gained popularity in the past decade by offering a viable and cost effective alternative to conventional forming processes. Hydroformed components offer benefits such as increased stiffness, lower weight, reduced scrap, and part/process consolidation. Tube hydroforming of aluminum alloys offers advantages of additional weight savings and increased corrosion resistance. The knowledge base for tube hydroforming of steel has been well developed in the past few years, but this knowledge is not directly applicable to tube hydroforming of aluminum extrusions due to the differences in the material behavior during forming processes.; The current research focuses on material behavior in two aluminum alloys (AA6063 and AA6082) employed in the tube hydroforming process. A systematic experimental and numerical study was utilized to determine the effects of process parameters that influence the hydroforming process. Initially free-bulge forming tests, with different end conditions, were used for model calibration and to determine the effects of friction, anisotropy, and material hardening behavior on the forming limit diagram (FLD). It was found that the extrusion welds affected the failure location of the tube hydroforming process. Therefore, a systematic study was conducted to quantify extrusion weld properties. This information was then utilized in a finite element (FE) model to determine the weld influences in the hydroformed tube. Axial feeding of material is not possible in many industrial applications where lateral material flow is hindered by bends or sharp changes in cross-sectional geometry, for example, engine cradle. Changes in final cross section shapes in these situations must come from pre-forming operations, such as crush forming. The effect of this forming operation in the formability of an aluminum extrusion was investigated. Finally, optimization methods were employed to the aluminum tube hydroforming process to determine optimum material feed paths and corresponding internal pressure paths for the successful completion of a hydroformed component using closed-die and T-branch die geometries. (Abstract shortened by UMI.)...