Problem with building domain

[dxvn818]

Hi all,

Recently, I use granoo-cooker to build a thin plate domain (82 x 12 x 2 mm) and I realize that the discrete elements are not fitted well with the support geometry. The geometry has an inclined angle as the below picture.





I would like to ask whether anybody could share with me the experience in using GranOO for thin plate problem ?

Thank you,
Vinh

[Damien André]

Hello Vinh,
Can you share with us your cooker input file ?

Thanks, Damien.

[dxvn818]

Hello Damien,

This is my cooker input folder. It is similar to what I built a box.

BuildDomain.gz

Thanks,
Vinh

[dxvn818]

Hello all,

And I would like to create the geometry of two coaxial cylinder with different diameters as the below picture, then let granoo-cooker to fill discrete elements in that domain. Is it possible to do that with granoo-cooker ? Could you please give me a hint ?



Thank you,
Vinh

[Cédric Hubert]

Hi Vinh,

The easiest way is to generate a .off file from the 3D geometry of your specimen.
Then use the tags/2.0/Tool/Cooker/inp/CookingBook-polyhedron.inp example to build your own DEM domain.

Best regards,
Cédric

[dxvn818]

Hi Cédric,

Thanks for your answer. Regarding the generation *.off file, I try creating a geometry with openscad, then export to *.off. However, it will be difficult for complex geometry. Is there any better way to generate *.off file, for example, convert directly from CAD model ?

Thanks,
Vinh

[Cédric Hubert]

Hi Vinh,

Sure there is!
I've never used OpenSCAD, but according to their documentation, you can directly export your geometry to .off file.

Best regards,
Cédric

[dxvn818]

Hi Cédric,

Yes, I can generate *.OFF file with OpenScad, then use the Plugin as your guide:

<PlugIn Id="_NewSupportShape" Type="Polyhedron" File="./off/coaxial_cylinder.off" ID="Boundary" />



Thank you and Regards,
Vinh

[dxvn818]

Hi all,

I use granoo-cooker for building the above figures with *.off generated from OpenScad, however, it seems that the scale of domain affect the results.

The geometry includes three coaxial cylinder with size:

r1 (radius)  =r3 = 30.5 ;  l1 (length) = l3 = 43

r2 = 12.5 ; l2 = 161

The geometry is scaled to milimeter and micro meter size.

a/ Milimeters:



b/ Micrometer:



I attach the case for your refernce:
cylinder.gz

I would like to ask whether we can fix the problem for domain with micro-meter scale ?

Thank you,
Vinh

[Damien André]

Damn !
If you apply a factor of 1e-6 it seems that numerical becomes high. My advice is build directly sample with the right scale.
Best regards, Damien.

[dxvn818]

Hi Damien,

I have just checked the *.off generated from OpenScad and realized that the numerical error also comes from OpenScad.  It only exports coordinates upto 6 decimal digits, so when I scaled the geometry in OpenScad to micro, it generates incorrect data.

Vinh

[Damien André]

Hello,
another solution is to use your favorite cad software > Export your part in *.stl > use the free software named "meshlab" to export in *.off format.

Have a nice day, Damien.

[dxvn818]

Hello,

I tried the way Damien suggested with meshlab, and granoo-cooker still does not work well. I think the numerous error now is in granoo-cooker when it reads *.off domain at micro-scale or smaller. However, granoo-cooker can generate and fill domain at micro-scale for the built-in type, such as box. It is so strange.

Vinh

[Cédric Hubert]

Hi Vinh,

Can you share your .off file so I can try it ?

Cédric

[dxvn818]

Hi Cédric,

Here are the *off files I used. The geometry is scaled in meshlab, then export to *.off.

cylindrical_specimen_micro.off = for domain at micro-scale
cylindrical_specimen_mm.off    = for domain at millimeter scale

cylindrical_specimen_mm.off

cylindrical_specimen_micro.off

Thank you,
Vinh

[Cédric Hubert]

Vinh,

Seems that we actually have a problem at these scales.
I'll take a look to fix the problem.

Best regards,
Cédric

[Cédric Hubert]

Vinh,

As a quick (and dirty) fix, you can modify the tolerance in file libAlgo/PolyhedronCore.cpp, at line 1161.
Replace the 1e-20 by 1e-30; then it should work fine.

I'll make a better fix later.

Let us know if it also work for you.

Thanks for reporting !
Best regards,
Cédric

[dxvn818]

Hi Cédric,

Yes, it works well for me too.

Thanks,
Vinh

[LE Ba Danh]

Hello,
I have a problem with CookingBook-polyhedron:


Can you help me?

Thank you,

Danh

[Damien André]

Hello Danh,
Please try with one of the off files provided in the "2.0/Tool/Cooker/off/" directory. If it works with this files, it means that the problem comes from your polyhedron. To fix problem with your off mesh file, You can use the "meshlab" software. It has a really good import/export tool.

Good luck, Damien.