Learning Forum

[ActiV]

nonlinear three point bending test_Trim.mp4

[peteroznewman]

Turn on Standard Earth Gravity which will provide a small force to keep the sample on the supports.

[ActiV]

thank you for the quick reply. I tried your solution, but now the simulation does not solve correctly (only added the earth gravity force). Please find attached a screenshot of the errors:
I will try adding weak springs next. Do you have a suggestion on how to proceed?
Thanks again.
EDIT:
Weak springs also not working. Model literally explodes (see video attached).

[peteroznewman]

Yes, add Weak Springs. I assumed that was turned on when I watched your video, but then you scrolled down and showed it was off. It was a fluke that the simulation solved.
You might also need to change the Analysis Settings, turn on Auto Time Stepping and set the Initial Substeps to 100.
A different way to get this to solve is to split the body in half and put a symmetry boundary condition at the center.

[ActiV]

thank you for the suggestions. I changed the analysis settings and added the symmetry plane. Although the analysis can be solved, when 'releasing' the bending test, the specimen disappears. See the images below at this transition point:
Why does this happen?
I get the following warnings too, maybe those are related;
4) Large deformation effects are active which may have invalidated some of your applied supports such as displacement, cylindrical, frictionless, or compression only.
3) One or more bodies may be underconstrained and experiencing rigid body motion. Weak springs have been added to attain a solution.
2) Solver pivot warnings or errors have been encountered during the solution.This is usually a result of an ill conditioned matrix possibly due to unreasonable material properties, an under constrained model, or contact related issues.Check results carefully.
1) Contact status has experienced an abrupt change.Check results carefully for possible contact separation.

EDIT:
Changing frictionless contacts to 0.2 friction didn't help. Adding a zero movement constraint in x-direction on the symmetry plane neither.
Maybe this helps to identify the problem:

Your help is much appreciated.

[hesamkeshavarzz]

First turn the large deformation on, .If it doesn't help, use Transient structural, upon my experience, structures with large deformation converge easier in this module.

[ActiV]

thanks for your suggestions. Large deformation is already on. I don't think transient structural is a suitable simulation type but I tried it anyway. Didn't work as the model either explodes or is not converging.