Influence of the natural aluminium oxide layer on ... - ALU-WEB.DE

Fig. 1: Tool concept for <strong>the</strong> visioplastic analyses in a porthole die
ibility <strong>of</strong> complex cross sections is based on
expert’s knowledge and cost-intensive prototyping.
A more efficient method to predict <strong>the</strong>
producibility and to reduce <strong>the</strong> risk <strong>of</strong> production
failure in advance is presently not available.
Hence, during <strong>the</strong> conceptual designing
<strong>of</strong> new automobiles not all possibilities can be
considered. One factor is <strong>the</strong> position and <strong>the</strong>
quality <strong>of</strong> <strong>the</strong> longitudinal seam welds. Insufficient
seam welds can influence <strong>the</strong> mechanical
properties <strong>of</strong> <strong>the</strong> pr<strong>of</strong>iles.
In this paper, <strong>the</strong> recent results <strong>of</strong> a transfer
project within <strong>the</strong> scope <strong>of</strong> <strong>the</strong> Transregional
Collaborative Research Center / TR10, which
is kindly supported by <strong>the</strong> German Research
Foundation (DFG), are presented. In this
project, extrusion companies, die makers,
automobile companies, extrusion s<strong>of</strong>tware
companies, and <strong>the</strong> Gesamtverband der Aluminiumindustrie
e.V. work toge<strong>the</strong>r to evaluate
how present simulation s<strong>of</strong>tware based
on finite element methods is able to simulate
complex industrial extrusion processes.
For <strong>the</strong> validation <strong>of</strong> <strong>the</strong> numerical results
in porthole die extrusion by visioplastic plastic
analysis a new modular die concept <strong>of</strong> a porthole
die was developed. This tooling concept
allows preparing <strong>the</strong> material out <strong>of</strong> <strong>the</strong> die
without post plastifications on <strong>the</strong> material
surface. Especially <strong>the</strong> analysis <strong>of</strong> <strong>the</strong> tribological
effects near <strong>the</strong> die walls can be done
[1,2]. The die is used for <strong>the</strong> production <strong>of</strong>
Fig. 2: Modeling <strong>of</strong> <strong>the</strong> process in Deform and HyperXrude
a rectangular pr<strong>of</strong>ile with a cross section <strong>of</strong>
40 mm x 10 mm. It consists <strong>of</strong> twelve single
parts. The fundamental part is a divided conical
part, which is necessary to extract <strong>the</strong> material
out <strong>of</strong> <strong>the</strong> die. Additionally, <strong>the</strong> material
which is prepared for <strong>the</strong> visioplastic analysis
can be inserted into <strong>the</strong> die again (Fig. 1).
Only a billet preparation would result in
high deformations <strong>of</strong> <strong>the</strong> contrast material inside
<strong>the</strong> feeders. In this case a determination
<strong>of</strong> <strong>the</strong> material flow and <strong>the</strong> tribological effects
on <strong>the</strong> die wall would be inaccurate. Due to
this, to analyze <strong>the</strong> material flow inside <strong>the</strong>
billet, <strong>the</strong> feeders and <strong>the</strong> welding chamber <strong>of</strong>
<strong>the</strong> die were filled by extruding an EN AW-
6063 alloy. The material was <strong>the</strong>n extracted
and prepared with <strong>the</strong> grid pattern technique
[1, 3]. In <strong>the</strong> vertical symmetry plane cylindrical
pins with a diameter <strong>of</strong> 5 mm were used as
contrast material. To visualize <strong>the</strong> horizontal
and <strong>the</strong> vertical material flow in one experiment,
<strong>the</strong> pins were inserted vertically and
horizontally in <strong>the</strong> symmetrical upper and
lower part <strong>of</strong> <strong>the</strong> die. An EN AW-4043A alloy
was used as contrast material. The distance
between <strong>the</strong> pins was 15 mm. But in <strong>the</strong> area <strong>of</strong>
transition from <strong>the</strong> billet to <strong>the</strong> feeder as well
as in <strong>the</strong> area <strong>of</strong> <strong>the</strong> welding chamber, different
distances were necessary. After preparation,
<strong>the</strong> material was reinserted in <strong>the</strong> modular die
for <strong>the</strong> experiment. After <strong>the</strong> preparation <strong>of</strong>
<strong>the</strong> billet <strong>the</strong> extrusion process was performed
SESSION SOFTWARE & SIMULATION
on a 10 MN extrusion press at <strong>the</strong> IUL to visualize
<strong>the</strong> material flow inside <strong>the</strong> die.
For <strong>the</strong> numerical analysis <strong>of</strong> <strong>the</strong> material
flow, <strong>the</strong> finite element method was used. The
simulation <strong>of</strong> <strong>the</strong> process was done with <strong>the</strong>
commercial s<strong>of</strong>tware HyperXtrude and Deform3D.
As initial data for <strong>the</strong> threedimensional
finite element models <strong>the</strong> geometrical
data <strong>of</strong> <strong>the</strong> experimental investigations was
used. Due to <strong>the</strong> fact that each s<strong>of</strong>tware uses
varying formulations a different modeling <strong>of</strong>
<strong>the</strong> process becomes necessary.
The implicit finite element code from Altair
Engineering uses <strong>the</strong> Euler formulation
where <strong>the</strong> material is meshed with a fixed
mesh. Hence, <strong>the</strong> overall material flow in <strong>the</strong>
process has to be modeled. It includes <strong>the</strong>
70 mm long billet (diameter <strong>of</strong> 105 mm), <strong>the</strong>
material inside <strong>the</strong> die, and <strong>the</strong> exiting pr<strong>of</strong>ile.
Additionally, <strong>the</strong> container and <strong>the</strong> die were
considered as rigid bodies to calculate <strong>the</strong>
heat transfer. Only a symmetrical part was
modeled to reduce <strong>the</strong> calculation time for <strong>the</strong>
quasi stationary simulation. The inflow velocity
was set to 10 mm/s.
In Deform3D, <strong>the</strong> Lagrange formulation is
used. Here, <strong>the</strong> finite element mesh is linked
to <strong>the</strong> material flow. Particularly in <strong>the</strong> simulation
<strong>of</strong> extrusion processes, where high deformation
occurs, frequent remeshing is required
in order to maintain a good mesh quality. In
this model components were discretized with
linear tetrahedral elements. The block with a
length <strong>of</strong> 80 mm and <strong>the</strong> material in <strong>the</strong> filled
die were modeled as one part, which has been
assigned a homogeneous initial temperature <strong>of</strong>
430°C. Both <strong>the</strong> container and <strong>the</strong> die were
assumed to be rigid. They were also discretized
in order to incorporate <strong>the</strong> heat exchange between
material and tools during <strong>the</strong> process.
The diameter <strong>of</strong> <strong>the</strong> block was chosen to be
equal to <strong>the</strong> inner diameter <strong>of</strong> <strong>the</strong> container
to increase <strong>the</strong> comparability to <strong>the</strong> HyperXtrude
model. Due to this, <strong>the</strong> upsetting <strong>of</strong> <strong>the</strong>
ALUMINIUM · EAC Congress 2011 73