impulse boundaries conditions

[Chris74]

hi all,
In the past, I had simulated a simple mechanical test using a rotating part (see mesh.png: rotary movement in A, blocked in B).
Now I would like to add an impulse in A, free in B. I would like to see the behavior of the part in B with an impulse.
First, I'm thinking of adding a spring at B in order to apply a specific mass there.
Next, I'm thinking of adding an imupse at the nodes at A, but I'm wondering if it's possible. I read the models manual, but couldn't find how to do it.
Do you have any tips or example to help me, or a similar test from elmerfem/fem/tests/?
Thanks

[kevinarden]

You can add an impulse at specific nodes by using Target Nodes instead of Target boundaries.
You can make it an impulse in transient by making it a variable of time
for example a 2000 force for 0.001 seconds

Boundary Condition 1
Target Nodes(x) nl1, nl2, nl3, ..
Force 1 = Variable Time
Real MATC "if (tx<0.001) 2000.; else 0.0
End

Similar to
viewtopic.php?p=20818&hilit=abaqus#p20818

[Chris74]

Thank you Kevin.
Your answer suits me well.

[Chris74]

hi Kevin,
Your answer helped me in the daming test (in the case of : Force in B, blocked in A), the results suit me very well.
Now, and it's my last request : I want to apply a tangential force in A in order to rotate the part. Until now, I used displacement conditions on the boundaries, and all is ok. Now I want to change the loading by a force in A but I have somme trouble : I understood that 'force 1' is associated to the normal force, and Force 2 and 3 for the tangential forces. I tried Force 2 with a value but the system diverge. Not sure that the tangential force are all on the same plane (Z-normal). I think I'm not going the right way. Do you have any advice ?
Thanks

[raback]

Hi

I think forces are always in cartesian directions.

What the code does is it assembles the equations in cartesian coordinates. Then it rotates the entries when glueing them into the global matrix. The Dirichlet BCs are then set in this global matrix and hence there the "normal-tangential displacement" affects the Dirichlet conditions of "displacement".

Typically pressure etc. is in normal direction. Also some slip coefficients may be associated to normal-tangential system. But other than that I think Neumann conditions are in cartesian system.

-Peter

[Chris74]

Thank you Peter for your quick answer.
So I undertand that to rotate a part from a hole, in my case, I have to use BC of Dirichlet on the nodes

[raback]

Maybe look at test case "ElasticBeamHinged3D". -Peter

[kevinarden]

If you apply the force with a BC boundary then you can turn on the normal-tangential option where Force 1 is normal to the boundary and Force 2 is tangential to the boundary. You can break up the boundary if you do not want to apply it to the entire hole. You have to turn on the normal-tangential option.