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Visualizing user-defined elements in Abaqus/CAE

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Posts: 42
Topic starter
(@aas0092)
Eminent Member
Joined: 16 years ago

Hi 😀

I have successfully completed a UEL, 3-D 8-noded linear user-defined element in Abaqus. I still need to verify the results, but it works.

I am trying to visualize the results in Abaqus CAE, and according to chapter 26.15.1 in the documentation:

Plotting of user elements is not supported in Abaqus/CAE. However, if the user elements contain displacement degrees of freedom, they can be [B]overlaid [/B]with standard elements, and model plots of these standard elements can be displayed, allowing you to see the shape of the user elements. If deformed mesh plots of the user elements are required, the material properties of the overlaying standard elements [B]must be chosen so that the solution is not changed by including them[/B]. If this technique is used, nodes of the user element will be tied to nodes of the standard elements. Therefore, degrees of freedom 1, 2, and 3 in the user element must correspond to the displacement degrees of freedom at the nodes of the standard elements.

[B]I am interested in displaying the deformed results in Abaqus CAE. How does one overlay with standard elements? Is it done in the input file somehow, or an the UEL source file?[/B]

Kind Regards

YK (Davinci)

10 Replies
Posts: 3998
(@jorgen)
Member
Joined: 5 years ago

It is great to hear that you got the UEL to work! Excellent!

The way to overlay elements is to add the elements into the input file, and then tie/join the DOF between the UEL and standard elements. It is not anything tricky about this, all you need to do is to create a new set of (standard) elements that have the same coordinate positions.

- Jorgen

10 Replies
Posts: 42
Topic starter
(@aas0092)
Eminent Member
Joined: 16 years ago

element deformation visualization

Hi

I managed to overlay the UEL with standard element by adding it to the input file.

The standard element does not deform, even though the nodes on the UEL do deform. I have tried changing the properties. (low stiffness for materials, but the overlaid element does not deform.

Any suggestions on how to make it deform?

Regards

Davinci (YK)

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Posts: 42
Topic starter
(@aas0092)
Eminent Member
Joined: 16 years ago

Boundary conditions

Hi again

My current setup is a 1-element axial displacement test.

I have modified the input file to apply the same boundary conditions on the overlaid element. This seems to have worked, and the overlaid element deforms with the user element.

There are problems though:

1. The stress values displayed are for the standard element, and not the UEL. (Although, I havent really defined stress in the UEL- I thought Abaqus would handle that part)

2. I will be using many more elements soon, with my real mesh. Editing the input file like this, I assume, would be very tedious. Is there no other way of working with the input file?

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Posts: 3998
(@jorgen)
Member
Joined: 5 years ago

I have not worked much with overlay elements, and unfortunately I dont know of an easy way to create and manipulate overlay meshes.

If you figure it out - let us know your approach.

-Jorgen

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Posts: 42
Topic starter
(@aas0092)
Eminent Member
Joined: 16 years ago

overlay elements

Greetings

I have managed to overlay the user element with a standard element, hence I can now visualize approximate deformation of user elements with more than just nodal displacements.

I ran a single element uni-axial displacement test on the user element.

(see image test05load.jpg) This was just a 100% displacement boundary condition on one of the faces of the cubic element. The opposite face is held fixed for all d.o.f.

I have a problem with the results though. (see image 002fin.png)

In this image, the X represents the initial node position, and the O, the deformed position.

It appears that the deformation of the nodes in the lateral direction are incorrect. (Although, in the longitudinal direction, the result is fine) I think this may have to do with the node ordering convention, and shape function order. (I have stuck to standard convention, but have also tried different variations, with some change, but no correct solution.)

I have attached images for the correct deformation on the standard element as well.

[U]Please advise on how I could fix this.[/U]

Kind Regards

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Posts: 3998
(@jorgen)
Member
Joined: 5 years ago

I am not sure what would cause that behavior. It appears that the volume is more or less concerved, which is probably a good thing.

Are you running the simulation in Standard or Explicit?

-Jorgen

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