FixConstraint and Nodeset

[nemesis]

Hello!
first of all I follow the FEM WB devloppment from time to time and I'm impress by the amount of work you guys did since one year! congratulation!!
now a little coment about the fixconstraint.
while setting up a fix constraint it's not possible to fix only one direction in the UI.
we have to manually modify the INP file by commenting the needed direction in boundary.
not a big deal and it's not a probleme for my personnal use, but it may be interesting from a professionnal point of view to have this option.

Code: Select all

*BOUNDARY
FemConstraintFixed,1
FemConstraintFixed,2
**FemConstraintFixed,3
FemConstraintFixed,4
FemConstraintFixed,5
**FemConstraintFixed,6

next point.
I'm trying to make an anylisis on a ski, for a friend who wants to build it's own model, and he was asking me if it was possible to estimate the bend of his design under a defined mass.
basically that's close to a school case study because he just want to have an idea of the bend of the core part which is just wood. So I get this:

ski_Test2.png (183.33 KiB) Viewed 2086 times

And that is exactly what I want as first step. so it's good
now my concern.
I use 0.17 and an extruded B-spline sketch for the profile of the ski so the upper side of the ski is one surface only. in the example I use the lower side of the ski which is split by edges (did it on purpose on the sketch) to have the requested face to apply the constraint only.

I was intending to use the "node set" function to define only the area that I want, and I can't figure out how it works.

I can select nodes, but how can I apply the constraint on those nodes?

[makkemal]

Fixed constraint is the wrong thing to use for the bending problem.
You should only use it at one location
For the rest use Prescribed Displacement and only fix them in upward direction

Hope it helps

[nemesis]

indeed if I use It for all location it works also.
thanks for the tip!

any idea about the Node set?

[bernd]

indeed if I use It for all location it works also.
thanks for the tip!

any idea about the Node set?

Yes, but this highly depends what would you like to do with this node set?

[nemesis]

Yes, but this highly depends what would you like to do with this node set?

Well my idea, (maybe a wrong one) was to use it just to locate the force or fix I want to apply as I don't have a "restricted" face to select, as the surface is coming from a b-spline extrusion.

Iss this suppose to be used for that?

[bernd]

this is best shown on your example. Would you post the FreeCAD file?

[nemesis]

sure

ski2.FCStd

(949.07 KiB) Downloaded 30 times

[bernd]

I'm not that good in PDN thus I made a simple cube example with Part instead of PDN. This is how I would create faces for applying some constraints. See attached file ...

[nemesis]

Thanks,
it works fine for a Flat face, but I need to find a Way for a curved face, I guess I need to project a sektch on the curved face. don't know if it feasible. I'm going to dig it.

just for curiosity what is the nodeset used for?

[bernd]

it works fine for a Flat face, but I need to find a Way for a curved face, I guess I need to project a sektch on the curved face. don't know if it feasible. I'm going to dig it.

see attached file. I use boolean intersection and extract the face and make a boolean fragment of the torus and the face to get the curved face on the torus

just for curiosity what is the nodeset used for?

I do not know. I never had a look at the code what it really does.

screen.jpg (264.9 KiB) Viewed 1918 times