Boundary condition limiting motion in the positive direction but not the negative

[AllNighter45]

Hey,
I'm new to Abaqus and could use some help. I was wondering how to define displacement limits such that the geometry can move in one direction and not the other. In other words, I want to constrain the motion in a certain direction rather than hold the nodes/elements at a specific, absolute coordinate.

More specifically, I have a bar and I want to constrain the middle of it as if there were an invisible ring over it. Therefore, I want the bar not to be able to expand out of the ring (if it were compressed), but I do want the nodes to be allowed to move within the ring (as to allow the cross-section of the rod to become thinner when stretched in tension).

Any advice yould be appreciated.

Thanks

 

[IceBreakerSours]

You have to two choices:

a) In the Interaction module, you can choose constraints. ABAQUS allows several types of constraints to be enforced. Check the *Equation constraint in the documentation. Use examples from the documentation to gain a full understanding, if the need arises.
b) In the Load module, fix appropriate degrees of freedom (translations/rotations etc.) by creating boundary conditions.

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083

 

[akabarten]

Hi,

I am afraid Abaqus does not offer constrains like you describe.
Such one-direction boundary condition is nothing more than contact.
I think the easiest way for you is to add additional geometry to model your boundary surface,
mesh and set as rigid body and next set contact interaction.
You can also use analytical rigid body if your shape is simple.

Regards,
Bartosz