Break press simulation?

General Questions
1

Greetings everyone,

I’m new here. My name is Artur.

I’m trying to simulate plastic behaviour of a sheet metal under break press.

I got some results when tried an extremely simplified version, but now I’m failing.

The files from my simulation are on my google drive – link attached:
https://drive.google.com/drive/folders/1lQoiZbz_johlm7tMnt2JzQEfMEkzQBa4?usp=sharing

What am I doing wrong?

2

Here are a few tips:

  1. Make the tools (punch and die) rigid by applying rigid body constraints to them. This will speed up the analysis. You will need to reapply boundary conditions to reference points of rigid body constraints though.
  2. Simplify the model as much as possible - you could e.g. use a 2D (plane strain) model here. Maybe also utilize symmetry (half of the model). All this will also reduce the number of necessary boundary conditions.
  3. Since it’s a static analysis (explicit dynamics procedure is normally used for metal forming analyses but it’s problematic in CalculiX, you could try implicit dynamics but it’s unlikely to help with convergence in CalculiX), you need to ensure BCs eliminating rigid body motions. For example, plane strain BCs (normal displacement fixed for front and back face) are usually applied to the blank in such cases. Avoid boundary conditions in contact areas.
  4. Add friction to contact property. This has negative impact on convergence but on the other hand, lets you prevent free movement (rigid body motion) if contact is properly established. Also, friction is important in metal forming processes.
  5. The mesh of the blank is way too coarse. Mesh it with hexahedral elements (using extruded mesh) instead of tetrahedrons.
  6. Ensure proper assignment of master and slave surfaces in contact. Master should belong to stiffer/rigid part with a coarser mesh.
  7. Don’t use perfect plasticity, add some hardening to aid convergence.
  8. You may need to enable Nlgeom. This may have negative impact on convergence but also increases realism of the simulation and is necessary to describe large displacements and deformations properly. Just avoid Nlgeom + rigid body constraints + 2D elements because it may cause non-convergence (known limitation).
  9. Look for some reasearch papers describing simulations of this kind of metal forming (V-bending).
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