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Dhondtguido / CalculiX

This repository contains the source files of CalculiX, a three-dimensional Finite Element Program (www.calculix.de).
GNU General Public License v2.0
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Rigid body constraint doesn't work with shell, axisymmetric and plane stress/strain elements in explicit dynamics #59

Open FEA-eng opened 9 months ago

FEA-eng commented 9 months ago

When I apply rigid body constraint to a shell model and try to run explicit dynamics analysis, I get the following error:

*INFO in cascade: linear MPCs and
       nonlinear MPCs depend on each other
       common node: 1 in direction 1

 *ERROR in nonlingeo: linear and nonlinear MPC's depend on each other
        This is not allowed in a explicit dynamic calculation

Here's a sample file:

https://www.dropbox.com/scl/fi/wwr8q9y3x74966y4czzry/RB_shell.inp?rlkey=3fw1z78wfhw2j1tqyngtuk16c&dl=0

It's also the case with rigid body constraints in axisymmetric and plane stress/strain explicit dynamics models.

Rigid body constraint is very useful in explicit dynamics since it can simulate rigid forming tools, impact targets and so on. Considering high computational cost of those analyses, simplifications like 2D elements are crucial so it would be great if this limitation could be removed.

FEA-eng commented 1 week ago

@Dhondtguido Unfortunately, this nasty bug/limitation hasn't been fixed in ccx 2.22.

victorkemp commented 1 week ago

Use solids to avoid all sorts of pain. There're not slower than shell/2D/axi in CCX, and being rigid, you can even make them from a poor quality 4-node tet mesh if the geometry is too complicated for C3D8/C3D6.