Reaction Forces on a Reference point constrained by a rigid body

General Questions
1

Hello,

I am running a non linear static 2D Axysimmetric simulation with 2 steps.

I created a point that I constrained to a face with a rigid body. Then I applied a displacement on that same point and wished to get the reaction force of the displacement. Could someone explain what do the RFs on that point mean. I have data going up and down instead of having some regular cuvre. Is there a way to either manipulate ma data or my simulation to obtain the desired results ?

Set up :

RBE2
RBE2512Ă—505 82.1 KB

Desired result on the left and obtained result by using the point’s RF on the right :

PLOT
PLOT1495Ă—539 116 KB

Thank you
VIR

2

The reaction forces that you obtained are essentially zero. There can be some issues with RF readings in 2D analyses in CalculiX (Zero reaction moment when reading from ROT NODE in 2D - CalculiX) so I would try with a 3D model. But it’s also likely that something is wrong with the analysis. Do the remaining results look correct ? Can you show them and possibly share the file ?

3

Thank you for the link. I had not seen it before. To sum this up, it is currently a bug?

Everything else is indeed working properly and this is why I haven’t been able to point out my trouble’s source.
I am yet unable to share this specific model but I will try the 3D simulation and will create a simplify version that I can share with you if you want to have a look at it !

Thank you for your time

4

I can’t say for sure yet but it’s quite likely.

Please do, if it happens to work in 3D then it’s likely a bug.

That would be very helpful.

1 Like
5

I tried you advice un went for a 3D model. However I am confronting an error.

ERROR in cascade: the DOF corresponding to **
** node 350299 in direction 1 is detected on the **
** dependent side of a MPC and a SPC

I saw that I am not the only having it but it seems pretty specific to each case. I split the contact and the surface where the force is applied by the ball thinking it would avoid any issues but did not. The node from the error is the top one from the ball such as :

image
image1389Ă—817 141 KB

6

It’s likely because this node belongs to rigid body constraint and symmetry BCs at the same time. You would have to exclude it from the rigid body or from the BCs.

7

Thank you but it then means that I should move all the one interacting with the symmetry boundaries.

I have not forgotten about your model but these have been busy and stressfull weeks !

8

Yes, but edge selection (or actually deselection) should make it rather easy. Just create new node sets this way and assign them to rigid body/BC definitions.

9

If the ball is completely constrained as rigid body (or just the surface), then the symmetry constraints aren’t needed at all for the ball. Just constrain displacement and rotation of the reference nodes appropriately.

1 Like