Super Hard Mesh

[eroque]

Heloo,

So i must mesh a very complex model, formed by a lot of iron bars in contact (see image - onlye reprsent a piece of my model).

Be cause the diameter of the bar is so small (4mm) and there are so many small interactions, abqus need a very fine seed to generate the mesh. I´m using 15 as Aproximate Global size, 0.1* 15 as minimum, and 8 seeds per circle (mesh curvature control. If i enlarge this values abaqus wonté generate mesh.

I really need to genreate a more coarse mesh. Any ideas ? There are so many contacts to do partitions in every single one.

In ansys, the automatic mesh tools handle this problem very weel.

 

[StefCon]

Hi,
How about using beam elements and then general contact? Should give a much more realistic stiffness response and a quicker calculation time.

If you really need solids then maybe altering the geometry by sweeping a square along the current geometry to make it rectangular. That would make the meshing easier. Beware of the stiffness when using coarse mesh. Abaqus defaults to reduced intregration elements (hex) which have bad bending stiffness.

 

[eroque]

Hello,

Thank u for your answer.

I am new using abaqus. This model is just to perform a thermal analysis, so mechanical characteristics are not important.

How can i use beam elements ? What are they ? i can´t find much information about them.

Thanks.

 

[corus]

You don't need to use contact unless your model is dependent upon the interaction of temperature with displacement, and as yours is purely thermal then it would be reasonable to assume that your rods are tied to the concrete or are an integral part of the structure so that only conduction occurs within the concrete block. If the mesh is too large then try considering only a section of the block and assume symmetry occurs to represent the whole block. That may be a reasonable assumption in the centre where the rods form a rectangular grid but would neglect the end effects where the rods form an arc.

 

[StefCon]

Hi,
I do not know how beam elements work when it comes to thermal models (especially thermal expansion). It was just an idea.

Here is information about beam elements: [URL unfurl="true"]http://50.16.225.63/v6.14/books/gsa/default.htm?startat=ch06.html[/url]

Here is how you create beam sections: [URL unfurl="true"]http://50.16.225.63/texis/search/hilight2.html/+/usi/pt03ch12s13s04.html?CDB=v6.14[/url]

Basically, if I remember correctly, this is what you do:
1 Create a material property
2 Create a beam section (round, diameter = x), assign material for beams
3 Create a wire at the center of your geometry (could be wrong on this one)
4 Assign beam property to wire
5 Assign orientation (very important) (In part display options, or something like that, you can render beams which allows you to see if they are correct. If they do not render it is usually the orientation that hasnt been applied.)

If you can live with many small solid elements, just try the general contact instead of finding contact pairs. You might also want to try this if it is hard to mesh: [URL unfurl="true"]http://50.16.225.63/texis/search/hilight2.html/+/usi/pt06ch69s06hlb04.html?CDB=v6.14[/url]

 

[Dave442]

Section 2.2.3 of the Users Manual covers how to define reinforcement in Abaqus.

Abaqus Analysis User's Guide, Section 2.2.3 - Defining reinforcement.