Simple Rubber Model

[FSAlight]

Hi Everyone,
I've only been using ABAQUS for a little while and I've encountered some small problems. I'm trying to create a simple model of a rubber undergoing axial elongation and I'm encountering some errors.

Here's my process.
- Create Part 3D-Shell-Planar
- Sketch simple geometric shape like a square.
- Create material with hyper elastic properties.
- Create a section - with membrane and the material
- Assign the section to the part
- Create an instance of the part
- Create an elongation step.
- Constrain the bottom edge with boundary conditions.
- Load the top edge via shell edge load
- Mesh the instance with M34D elements

However when I go to run the job I get the error
INVALID LOAD TYPE ON ELEMENT X INSTANCE RUBBER TEST PIECE-1. LOAD TYPE EDNOR IS NOT VALID FOR ELEMENT TYPE M3D4R

What's happening here? Am i making rookie mistakes or is something else wrong?

Thanks,
FSA

 

[rstupplebeen]

I assume that you meant M3D4 not M34D.

I think that your loading is not appropriate for a cylindrical membrane element. See 28.1.1 in the analysis user's manual.


Rob Stupplebeen

https://sites.google.com/site/robertkstupplebeen/

 

[FSAlight]

Hi Rob,
But in my ABAQUS analysis user manual 28.1.1 refers to Connector elements?
From the User's manual it says that M3D4 is a general membrane element. Where as a cylindrical membrane element would be more along the lines of MCL6?
Or am i missing your point?
Thanks

 

[rstupplebeen]

I stand corrected must have been too early for me.

If you post your model I will give it a look.

Rob Stupplebeen

https://sites.google.com/site/robertkstupplebeen/

 

[FSAlight]

Well here it is along with the journal file in a zip.
I've been rifling through the user manual for hours to see what I've done wrong.
Hopefully you can shed some light on it.
Thanks

 

[rstupplebeen]

Instead of an edge load try a displacement or load a reference point and constrain the edge to the point.

You need to add a density to your material. This can be tricky so make sure your units are right. If you are in mm then water is 1e-10.

I hope this helps.

Rob Stupplebeen

https://sites.google.com/site/robertkstupplebeen/

 

[FSAlight]

Thanks for the suggestions.
I've added the density so I'm no longer getting that error.
However I'm still not sure on what's making it say that the membrane elements I'm using are not able to take the load which I'm applying.
Anymore suggestions?
Thanks

 

[rstupplebeen]

In my work when I hit a wall like this I just try a different method and move on. Try my 2 suggestions from above and if they accomplish what you need your job is done.

"Instead of an edge load try a displacement or load a reference point and constrain the edge to the point."

I hope this helps.

Rob Stupplebeen

https://sites.google.com/site/robertkstupplebeen/