For a simple flat surface, is it possible to constrain the displacement in one direction of the axis (say +ve y axis) while allowing it in the other direction (say -ve y axis)? Normally, applying displacement constraints, fix the displacement in both directions.
Hi Waseem Akhtar
You can create a reference point and constrain it with the surface you want the displacement using a linear equation. Then apply a displacement at the RFP and choose the direction of axis you want.
Allan Waithira thank you for the reply.
Actually, I don't want to apply any displacement. I want to constrain the surface nodes from moving in one direction of axis and let it displace in the other due to the action of internal forces / stresses generated during the analysis.
Waseem Akhtar
Have you tried using the "Displacement" boundary condition in the "Constraints" module? To model a one-way restraint, you can specify a non-zero displacement in only one direction. For example, if you want to constrain the displacement of a flat surface in the positive y-direction while allowing it to move freely in the negative y-direction, you can specify a non-zero displacement in the positive y-direction and a zero displacement in the negative y-direction and then perform the node selection procedure.
Allan Waithira thank you for your reply.
I guess you mean to create a reference point and tie it with the surface that is required to be constrained. And apply a very very small value of displacement in the direction in which the displacement of the surface/nodes is required to be restrained. Is it? Even in that case, only one value of displacement can be entered as can be seen in the attached figure. How two values (for +ve and -ve direction) can be specified separately.
If otherwise, could you explain a bit more.
Hello Waseem Akhtar,
could you please provide some more information about your model, such as an assembly image? If I understand correctly, you want the surface to be able to move if it is pushed down, but not if it is pushed up. Is that correct?
Maybe this could be done by using some additional parts and interaction between them.
Sincerely,
Pavlo
Thanks Pavlo Pavliuchenko ,
Imagine a flat deformable plate on the top of another flat rigid support which does not allow the plate to displace downwards. The upper plate is fixed by Encastre BC at its four bottom corners whereas its central regions may displace in upward direction due to the stresses generated during the loading process.
I tried to model the lower rigid support and defined Contact interaction between it and the upper deformable plate but it causes the analysis to become too slow and have convergence issues. btw I tried both friction and frictionless contacts both as general and surface to surface formulations.
Just thinking of a smart way to handle it!
Hello Waseem Akhtar,
If I understand correctly, it may be possible to solve the problem of node displacement in one direction by using additional flat, rigid support. However, this could potentially cause convergence and time issues during simulation. My suggestion would be to attempt to solve the problem using this approach rather than trying to fix node movement in a specific direction. In my experience, when surfaces are defined to interact and are initially in the same position (such as one surface lying on top of another), this can lead to a significant decrease in the increment time to resolve the issue. I recommend using "Contact Controls" when defining the interaction between surfaces:
1) If you are using the Standard step:
Contact Controls -> Abaqus/Standard Contact Controls -> Automatic Stabilization.
Then, in the "Interaction" menu that defines the interaction between the surfaces, select the created Contact Control.
2) If you are using the Explicit step:
Contact Controls -> Abaqus/Explicit Contact Controls -> Use the default values.
Then, in the "Interaction" menu that defines the interaction between the surfaces, select the created Contact Control.
Please try this and let me know if it helps in any way.
Sincerely
Pavlo
Hi Pavlo Pavliuchenko
I defined, Contact Controls -> Abaqus/Standard Contact Controls -> Automatic Stabilization, using default values but it didn't change the solution much, there were convergence issues
I think defining contact would always have problems / time issues since the upper plate is deformable and it's contact condition would be changing during the course of simulation due to deformation of it's bottom surface in contact with the rigid support.
There should be some more practical way to restrict it's movement in one direction of axis rather than modeling a rigid support in contact. Thinking.....
Thanks.
Connector elements with stop capability can be useful.
http://130.149.89.49:2080/v2016/books/usb/default.htm?startat=pt06ch31s02alm34.html
Victor J. Аdlucky Thank you for your reply. I'll check if connector elements can be useful in this problem.
Waseem Akhtar were you able to resolve the problem?
I'm also facing a similar issue with my model. If you have found a solution please share. Thank you very much.
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