Apply force to part of face in FEM

[bartbols]

Hi,

I am new to FreeCAD (and loving it!) and was wondering if in FEM analysis it is also possible to apply a force to only part of a face, instead of to the whole face at once. If this is possible, how do I define the force application area on the face? I managed to work around it by adding an object with the shape of the desired force application area with a very small thickness, but I hoped there is a neater solution.

Any help is appreciated!

Cheers, Bart

[r-frank]

Hello bartbols.

Welcome to FreeCAD and the forum.

Some commercial CADs (for example Solidworks) allow to split a face by using a sketch projected on the face.
As far as i know not (yet) possible in FreeCAD.

Depending on your design turning automatic refinement off and using the left over lines from the basic shapes
may work - I haven't tried that yet.

So the solution you described seems to be the only practical solution left at the moment.

Besides, if you split your face or if you use an additive/subtractive element with minimal height will leave you
in both cases left with the basic FEM-problem.
Inside the "boundary" you have a constraint (for example a fixed constraint for a restraint or a force consttraint)
and outside the boundary you have no constraint.
This sharp contrast at the boundary will pose a challenge for good meshing and will most likely cause a singularity
when calculating your goal(s) with the solver.

Roland

[fandaL]

I tried only 2 very simple examples, and it worked in this way:
1) if the face is planar (e.g. face of a cube):
create a sketch on that face and extrude it inside into the base volume. New "pad" is possible to mesh and apply forces or displacement on a face created by the extruded sketch.

2) if the face is not planar (e.g. face of a cylinder):
create a new sketch, which is possible to extrude into (or from) the base volume. Then create intersection of the base volume and the extruded one. Next step is to create a union of the last intersection and the first base volume. This union can be meshed and a new face used to apply force.

cylinder_pad_intersection_union.png (44.62 KiB) Viewed 1840 times

In both of them resulting outer geometry is the same.

[bartbols]

Hi,

thanks for your reply. The suggestion to extrude the face inside the volume worked for me. It would be nice though if faces can be split just like in SolidWorks so I'll see if I can put in a feature request elsewhere on the forum.

Bart