Hello all,
I wrote you about this topic a few weeks ago.
I would like to apply a force and a moment through rb3r in ccx.
I used the following card but It does not work properly on a curved surface (as the manual shows) in ccx (different displacements than Abaqus)
*COUPLING, REF NODE=501, CONSTRAINT NAME=C1, SURFACE=B1_INT
*DISTRIBUTING
1,6
So to apply a force I used the SURFACE TRACTION and I have a excellent correlation with Abaqus.
Now I would like to apply a moment and of course surface traction generates only forces.
For this reason I created an equivalent traction like this
where the forces are moment/arm (the arm is calculated in Prepomax defining the position of the reference node of the resultant force.
The results are more in line with the Abaqus results but there is still a difference 13%.
I share you both model (abaqus and ccx). https://we.tl/t-GdsCdHt2gi
What is your feedback?
Thank you
This is an unfortunate limitation. Maybe you could try an older version of CCX (pre 2.19 if I remember right) which had a different formulation for *DISTRIBUTING that might have worked better on curved surfaces? It did have its own errors in some cases though, so don’t expect any miracles.
Can I ask why you want the moment to be distributed in the particular way that RBE3 does it? That doesn’t model any practical physical mechanism and is more just an elegant idealization for parameterless distribution of loads. Is RBE3 really more correct than this pair of opposite tractions?
Becuase I have a first step where I solve the interference. So if I use rbe2, it affects the deformation of the bearing.
I mean why RBE3 instead of just two tractions like you have, or some more realistic elastic material transferring the load into it? What’s the physical meaning of tension applied to the surface of the bearing race?
In abaqus we use rbe3 to apply force and moments. It is just to find a correlation.
However two traction does not work correclty. I have different dispacements.
Correlation between?
I know RBE3 is nice and it would be great to have it in CCX, but I don’t see how it makes physical sense here since it looks like a tension load on the surface of a bearing race.
The file attached contains a model with distributed moment applied to a surface with double constant curvature. Could you please run it with Abaqus and gave us the results?
For Mx maximum Uy=
For My maximum Uz=
For Mz maximum Uy=
You just need to change *Cload for values 4 , 5 and 6
*CLOAD
1,4,10
*CLOAD
1,5,10
*CLOAD
1,6,10
It’s a moment of 10 Nm on each of the main axis so we can compare the discrepancy an eventually find a workarroud to get as close as possible.
Be sure to use C3D20R elements.
Hello,
I run test on Abaqus and the results looks good (the same results). I tried also with C3D10 and I got good results. In my model I used C3D4 just for memory. Now I switched on C3D10 but I have always bad results. What could be the problem in my model? In this first sterp(interference results are the same, but when I apply moment they are very different as showed in the picture
As the test is in good agreement with Abaqus for the isolated moment, I would proceed as follows:
1-Check if some BC may have change from moving from Step 1 to Step 2.
Inspect how reactions evolve at the Boundary and if they are all in balance and as expected compared with the input forces/moments. Specially between the end and beginning of each step.
Are you using Perturbation parameter?. Are you redefining the BC in the new Step?
2-Check if contact state may have change from moving from Step 1 to Step 2.
Is the contact clearance maintained in-between steps without additional loads?
If traction is responding as expected, the problem could be in the tangential direction.
Have you set up tangential stiffness or Friction in your contact parameters?. Are they the same values as Abaqus contact parameters?
How do final CDIS and CFS compare with Abaqus?.