Penetration in model after defining thickness

Altair Forum User

Hi, 

 

I've working with a model defined with shell finite elements on Hypermesh 13 and have been having trouble after the definition of the properties cards of the model. When I specify the thickness of the surface, a lot of penetrations (on more than 2000 elements) appear on my model and the automatic fix tool doesn't seem to work on them. I've verified and there aren't any geometrical intersections on the surfaces. My questions are:

 

How can I avoid such problems or configure the model in order to prevent them?

When defining the thickness of a surface, this surface is assumed to be a mid plane so the thickness is distributed equally to both sides? Can this be modified?

 

Thank you in advance for your help.

 

Altair Forum User

Hello @Sebastian,

Greetings!!!

 

Penetration/ Intersection check is a must, before you set up for run. However, to resolve those issues, I would suggest you to manually translate the elements/nodes or use element offset (in 2D>shell offset) option, instead of using automatic fix tool.

 

To avoid penetration/intersection , make sure, your mesh is on the mid-plane.

 

Suppose, there is penetration/intersection in the geometry itself, then you need to make educated guess to resolve it.

 

'When defining the thickness of a surface, this surface is assumed to be a mid plane so the thickness is distributed equally to both sides? Can this be modified?'

For this Q, you could define single side thickness, instead of assigning thickness to mid-surface mesh, and sometimes, this could be used to avoid penetration/intersection.

 

You could share your model, so that we could be more helpful. Also, let me know, if there are any corrections in what I told.

 

 

Thanks & Warm Regards,

Akshay S. Patil

Altair Forum User

Hello, Akshay.

 

Thank you for you reply. 

 

I can't figure out how to manually translate the element or nodes as you indicated. Can you please provide instructions on how to use this tool and the shell offset?

 

Regarding the other question, can you please also let me know how can I define single side thickness?. 

 

I attach the model below.

 

Thank you.

Unable to find an attachment - read this blog

Altair Forum User

Hello @Sebastian Henao,

 

Greetings!!!

 

When you do pentration/intersection check, you could isolate the intersecting/penetrating elements, (the option in black box)

 

In you model, in the helighted region, there is a free edge, (fix it by equivalence the node in that region) , and in some other areas as well.

 

Also, there are a couple of duplicate elements in your model, which needs to be deleted.

 

Therefore, in general, before you do penetration/intersection check, 

Check for connectivity, duplicates, elemental quality criteria, and normals.

 

Regarding, single side thickness, the mesh needs to be one of the sides, instead of the mesh being at the middle, and you need to make changes in the property, in case of LS-Dyna NLOC.

 

 Hopefully, this resolves the issue.

 

Thanks & Warm Regards,

Akshay S Patil

Altair Forum User

Hello, Akshay

 

I am no able to find the free edges you mention but I already deleted the duplicated elements. 

 

Can the single side thickness be defined on RADIOSS block 120?

 

Thank you.

 

 

Altair Forum User

Hello @Sebastian Henao,

 

In you model, check for edges option with tolerance of 0.1

 

<?xml version="1.0" encoding="UTF-8"?>

 

 

I am not familiar with interaction of Radioss.

 

If you find it, please do share the information.

 

 

Thanks & Warm Regards,

Akshay S Patil