## Simulation Mechanical and Multiphysics

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# adding bc to prescribed displacement

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Hi

I would just like to know how is it possible to add a bc to a node where there is still a prescribed displacement (of course in another dof).

Each time i try, i have the error message saying : prescribed displacement non active

Thanks!

# Re: adding bc to prescribed displacement

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BC and PD are allowed to be applied on different DOFs of a node.

I bet your model needs double-check.

If your model is complicated, you can create a simple one ( maybe just one element) to see if there is still the same problem.

Of course, you are also welcome to share your model here.

If this response answers your concern, please mark it as "solved".

# Re: adding bc to prescribed displacement

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I remember also having this problem. As far as I know, though, you can simply att the other BC as a prescribed displacement by use of a "custom" vector though. For example, if you set a prescribed displacement along the X-vector, I think the node is still free to move in the Y-and Z-directions. However, if you make a prescribed displacement with a vector of (X,Y,Z) = (1,0,0), the node will be constrained also in Y and Z.

I'm unsure how this works with rotations at the same node. Does anyone know if you can apply both a rotational and translational prescribed displacement at the same node simultaneously? I don't see why it shouldn't work...

# Re: adding bc to prescribed displacement

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I attached a MES model here.

Both BC and PD have been applied on nodes along the top surface.

If this response answers your concern, please mark it as "solved".

# Re: adding bc to prescribed displacement

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yes, as Bjorn explained, try using Custom vector!

# Re: adding bc to prescribed displacement

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OK, i will try and let you know.

And i also remember that sometimes, it is better to input a custom vector than the X Y or Z one. But it shouln't be the case.

ALAIN

# Re: adding bc to prescribed displacement

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Here is a model where i add a displacement in the Z direction (defined by a customer vector) and constraints also the X and Y direction.

And there is the error message

The file is here : http://www.yousendit.com/download/ZGJlU2Vxa0REbUpF

# Re: adding bc to prescribed displacement

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The BC is to constrain Tx and Ty, and the PD is (0,0,1), so there are incompatible on X and Y direction.

the PD should be applied on only Z direction, instead of "Vector".

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# Re: adding bc to prescribed displacement

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OK i see i can not define the vector but only clic on scalar X, Y or Z

If i input the vector as custom, it is not accepted.

So what is the solution if the displacement direction is not in those global directions.

Thanks

# Re: adding bc to prescribed displacement

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Since you constrain, for example, X direction, your loads/PD on the same direction will make no sense.

For example, if X is constrain, and you want to apply PDs along both Y and Z. Then you have to apply them separately.

In another word, there should be two PDs in the model, one for Y and another for Z.

If this response answers your concern, please mark it as "solved".