Deformations in Idealized 2D Extrusion Welding

Abstract

Metal flow inside the container and in the metal behind a butt-ended die bridge in idealized aluminum extrusion welding has been investigated by FEA and experiment with respect to the deformation of the material flowing around the bridge and into the layers close the extrusion seam weld. Along the mid-axis of the extrusion process the effective strain subjected to the extrusion material can be determined in three different ways. One way is to determine the strains from grid pattern experiments that reveal the real deformations. When it comes to FEA there are two options; the strains can be determined from the initial and final positions of a number of material points distributed along the mid-axis of the material, where after traditional theoretical strain-equations can be used to calculate the effective strain distribution along the axis. Another possibility is to use the post-processor of the software to calculate the strain distribution. In this work the effective strain distribution along the mid-axis of the billet inside the container volume were determined by all these three methods. The effective strain in the thin layer of the squeeze zone ahead of the dead zone in front of the die bridge determined from the experiments was found to be much larger than the strains elsewhere along this axis. The same was the case when effective strain was determined by FEA from the computed position of the points, but this strain value was predicted approximately 10% lower than the corresponding value from the experiments in the layer with the heaviest strains. However, when this effective strain distribution was calculated by the post-processor of the software the high-strain layer in the squeeze zone was not revealed at all, instead the effective strains were predicted rather even over the whole length of the mid-axis. Corresponding effective strain distributions were determined along the mid-axis of the extrusion material in the weld chamber also, and after outflow of this material into the extrusion seam weld of the resulting profile where no experimental information is available. When this effective strain distribution was computed by FEA, based on initial and final position of points, very different strain values were obtained as compared to when same strains were collected directly from the post-processor. It is believed that the first results, i.e., the effective strains computed from the points are quite accurate, while those values calculated by the post-processor are less reliable.