Exporting Abaqus Dry Fibre File

[eswe004]

Hi,

I was wondering whether it is possible to specify the element size when exporting an "Abaqus Dry Fibre File"?
Can a finer mesh be generated?

(Not sure if there is a simple solution to this that I have simply missed).

Thanks in advance,
Elinor

[louisepb]

Hi Elinor,

Apologies for the delay in replying - I've been on holiday.

You can change the density of the mesh generated by changing the number of section points around the circumference of the yarn. The algorithm for generating the mesh uses these points so if you increase the number the mesh will become finer. Use Yarn.SetResolution (iNumSectionPoints)

Hope that helps,
Louise

[eswe004]

Perfect.
Thanks!

[eswe004]

Hi,

Just following up on this, I have been increasing the resolution, but it doesn't seem to increase the number of elements in the thickness of the yarns (only around the circumferenec). Is there a different command to control this?

Thanks,
Elinor

[louisepb]

Hi Elinor,

That is a result of your section having a small height in relation to the width. There isn't an option in the user interface to address this.

From a script you could use the CSection::SetSectionMeshLayers function which will set the number of layers (which must always be an even number). You would need to get each section and set the number of layers for each.

Hope that helps,
Louise

[eswe004]

Hi Louise,

Thanks for that.
I have now used that function to increase the number of layers, but as you can see in the picture attached, have not obtained the result I was after.
Is there a way to ensure that the elements are more regular?

Thanks,
Elinor

[louisepb]

Hi Elinor,

I'm afraid the results are a function of how the algorithm works. It looks here like you asked for 14 layers? I think that if you reduce the number of layers you will end up with something more sensible. Essentially the number of layers dictates how many rows there are in the grid. If this is large then, as the number of points around the edge stays the same, there must then be fewer columns. Hopefully something in between this and the one you started with would give you a happy medium.

Louise

[eswe004]

Hi Louise,

I have been having some trouble with Abaqus compaction simulations, and I think it could be a result of textile mesh that I use. I want to export different meshes of the same textile model to try out a few things, but have been having some difficulties.

1) I have not managed to successfully use CSectionMeshTriangulate function. This is the code that I tried to use before exporting the Abaqus dry fiber file. The exported mesh however, still has elements with a
rectangular cross section:

Code: Select all

section = CSectionRectangle(0.8, 0.1)
SectionMesh = CSectionMeshTriangulate()
section.AssignSectionMesh(SectionMesh)
textile.GetYarn(0).AssignSection(CYarnSectionConstant(section))

2) I have tried to increase the number of layers in the cross section, but again, this isn't working for some reason. (I am not sure why, as I had it working in previous posts). I am using this code and the exported mesh still has 2 layers in the cross section

Code: Select all

 sectionX = CSectionLenticular(0.8, 0.1)
sectionX.SetSectionMeshLayers(8)
Yarn.AssignSection(CYarnSectionConstant(sectionX))

3) Is there a way to avoid the sharp edges created at the left and right sides of the tows? I want the mesh to be more rounded at the edges. Even if I have an elliptical cross section, the cross section of the mesh still looks like it is lenticular (with a sharp edge).

Thanks a lot in advance,
Elinor

[louisepb]

Hi Elinor,

I have to admit that I haven't used the CSectionMeshTriangulate function before. I've just tried it for a simple yarn using the code snippet below. It seems to work fine. If you replace the CSectionRectangle with CSectionEllipse then it triangulates the ellipse and then exports the dry fibre with a mesh with wedge elements. It seems to load into Abaqus fine. I haven't tried it with non-constant cross-sections - this may not work as I guess that the triangulated meshes then won't match. I'll investigate that at some point.

I'm not sure what the problem with the layers is. I've just tried it (as given below) and it seems to work fine. Are you looking at the volume mesh in the GUI? Have you tried re-rendering it? (Switch Render Textile Volume off and then back on again).

The only way to avoid the sharp edges is to increase the resolution (ie the number of points around the section). The points are distributed evenly around the section so if you have a very thin section this results in a point at the edges. The effect will improve if there are more points.

Hope that helps. Let me know if you have any more problems, especially with the triangular mesh sections as I'm not sure that anyone has used these in earnest before.

Louise

[eswe004]

Hi,

I am not sure what is happening. When I try to use the wedge elements and increase the number of layers in the cross section I can see the updated volume render fine in TexGen. However, I then export it (Export--> ABAQUS File --> ABAQUS Dry Fibre File...) and the exported mesh has the standard cross section (rectangular elements with 2 layers) as if I didn't make any modifications. On top of that, after I export from TexGen, if I update the volume render, it goes back to the standard cross section.

Is this happening for you too? Or when you import the mesh into Abaqus does it have wedge elements (and more layers?)

Thanks,
Elinor

[louisepb]

Hi Elinor,

I'm not sure exactly what is going on with what you're doing. The number of layers only applies to the rectangular mesh. The triangulate applies a triangulation algorithm for which the layers are meaningless. As the code is written at the moment the triangulation can't be changed. I've attached a couple of screenshots from the files exported to Abaqus. You can see the differences in the triangulation as the depth of the ellipse increases.
Could you send me the commands that you're executing and I'll see if I can try and replicate what you're seeing?

TriangulatedVolumeMesh.png (12.48 KiB) Viewed 21273 times

TriangulatedVolumeMesh2.png (12.14 KiB) Viewed 21273 times

Best regards,
Louise

[maryam_sodagar]

Dear Louise

I decided to ask my questions one by one in forums. But thank you and your team so much for this useful software which have made textile scientists works easier.
When I export the dry fibre to abaqus and do the tensile force and assign uniaxial load, it has excess distortion in wedge elements so I think it is because of the mesh size in wedges. If I make them coarser, the wedge elements surface area might be bigger and the tension might be lower so the distortion may not happen. What should I do to make the wedge elements coarser? I will attach the distortion picture in wedge elements.

Untitled.jpg (57.24 KiB) Viewed 20434 times

[louisepb]

Hi Maryam,

You can change the mesh size by changing the yarn resolution in TexGen. If you use yarn.SetResolution(n) this will change the number of section points around the edge of the yarn to n and this is used to generate the volume mesh when using the dry fibre export.

My colleague suggested that you might also consider changing the time steps used.

Hope that helps,
Louise

[maryam_sodagar]

Hi Maryam,

You can change the mesh size by changing the yarn resolution in TexGen. If you use yarn.SetResolution(n) this will change the number of section points around the edge of the yarn to n and this is used to generate the volume mesh when using the dry fibre export.
Can I edit the .tg3 file and change the resolution and then export to abaqus?

My colleague suggested that you might also consider changing the time steps used.

Hope that helps,
Louise

Thank you so much. I am sorry if I am not expert enough to use python codes. When I generate the model using texgen wizard and assign yarn properties and cross section and etc. then I should just write yarn.SetResolution(n) or I should first define a class and so on? would you please help me what should I write in python consule step by step to assign a different resolution?
About time step I tried to change it but the result was the same.

Thank you for your help.

[louisepb]

Hi Maryam,
You can use the Python console to set the resolution for a textile created in the wizard.
You will need something like:
textile = GetTextile('textilename')
yarn = textile.GetYarn(yarn_number)
yarn.SetResolution( resolution )

You will need to do this for each yarn. Either write a loop or do it manually one by one if there aren't many yarns.
Best regards,
Louise

PS. Please don't copy and paste the previous message into your message. It just clutters the thread up and the previous message can be seen in the thread anyway.