Learning Forum

[mmia1]

Hi

 

I have some confuison in *BOUNDARY_PRESCRIBED_MOTION_SPC. I am applying displacement as prescribed motion at all nodes at bottom plate of a tank in Y direction. I then applied *BOUNDARY_SPC restricting the movements in X and Z and rotations in all three directions. The card looks like below:

 

 

 

 

 

I found some online resources which states, "you shouldn't need both *Boundary_prescribed_motion and *Boundary_spc. You should just be able to create a node set and use *boundary_prescribed_motion_set where you will reference the node set and use your current settings. The DOF in the boundary prescribed motion card will restrict motion to only that direction so you don't need spc." 

 

But when i don't use *Boundary_spc then the model got aborted. However, if I use *Boundary_spc restricting the movement in other two directions (X and Z including rotations in all three directions), then the model works fine. 

 

Please provide me some insights on this. Thanks again.

 

Regards,

[Bernd Hochholdinger]

You can use both: BOUNDARY_PRESCRIBED_MOTION_.. as well as BOUNDARY_SPC. But you should take care that there are no conflicts between both definitions like for example fixing a  certain degree of freedom (DOF) via BOUNDARY_SPC and at the same time applying a displacement boundary condition to that DOF via BOUNDARY_PRESCRIBED_MOTION_...

You also can define BOUNDARY_PRESCRIBED_MOTION for all DOFs of intertest. For the DOFs that should be fixed you simply can define zero displacement curves over time.