On bend-stretch forming of aluminum extruded tubes — II: analysis

Part II describes a two-dimensional model of the bend-stretch-pressure forming process, which assumes that the tube shape and all applied loads are uniform along the length. This simplification results in a significant improvement in computational time over corresponding three-dimensional models. The model is validated through comparisons with experimental results discussed in Part I and its application to the design process is illustrated. The model is then used to study the current manufacturing process and to evaluate some possible alternative loading histories. The effect of tension and pressure on the cross-sectional distortion, springback and net elongation are discussed in light of the predictions. Additionally, the merits of changing the tension and pressure after forming are discussed. The simulations and corresponding experiments are used as the basis for a design methodology for selecting the order and magnitude of the loads applied during the forming process.