Investigation on Aluminum Tube Nosing in Conical and Hemispherical Dies: Numerical Analysis and Experimental Verification

In this work, a finite element analysis was performed and experiments were carried out on the nosing process of commercial - purity aluminum tubes using conical and hemispherical dies. A new tool and punch design were introduced. The design included a front plunger to be inserted inside the original tube to enhance axially. An outer sleeve was also used constraining the tube to eliminate bulging. The influence of the process parameters, namely initial tube wall thickness, conical semi-die angle, coefficient of friction and die shape on the deformation mode, critical nosing ratios of formed tubes, thickness distribution and failure type were checked using the finite element analysis. Experimental results verified the trends of the numerical analysis. Experimental nosing loads increased with the increase of tube thickness, semi-die angle, and coefficient of friction. Experimental nosing ratios were increased by the increase of tube thickness. Such ratios for the hemispherical die showed a little increase than those for the conical die having semi die angle 15°. The less correlation between experimental and finite element predictions for the thickness strain was shown in the part of the deformation zone at which the section transfers from the straight to the conical section. But that correlation became good near the end of forming part. Experimental wrinkling, folds, and earing defects were in agreement with those modeled by the finite element simulation and no bulges were noticed in the un-deformed part due to the case of the new design.