Unrealistic Volume Fraction

[maryam_sodagar]

Dear Louise


When I render the orientation in texgen, the error is about unrealistic volume fraction (1.0057)
but actually my yarn properties are different and I calculated total fiber area and num of fiber and etc. by using definition in Martin PhD thesis.
I have 3 sample (Plain, Twill, Crowfoot Satin 4) and just the last one has this problem.
If anybody knows how to solve this problem, Please let me know too.
I am looking forward to your reply.

[louisepb]

Hi Maryam,

Please could you be more specific about where this issue is arising? (What your model is and what data you are inputting)

Thanks,
Louise

[maryam_sodagar]

Dear Louise

How can I figure out where it happens?
when I render fibre orientation I see this warning in Texgen Output.

My material properties:

Warp:
Yarn linear density: 135 e-6 (135tex)
Fibre density: 2600
Total fibre area: 5.1921 e-8
Fibre diameter: 13 e-6
Fibre per yarn: 387
Young modulus : 489 (when warp yarns are in y direction, should I put young modulus in Y direction or X? )
Shear modulus: I do not need it and I do not have it too, let it be 1!
Poisson ratio: 0.23

Yarn linear density: 35 e-6 (135tex)
Fibre density: 2600
Total fibre area: 1.3416 e-8
Fibre diameter: 13 e-6
Fibre per yarn: 100
Young modulus : 603 (when weft yarns are in X direction, should I put young modulus in Y direction or X? )
Shear modulus: I do not need it and I do not have it too, let it be 1!
Poisson ratio: 0.23

areal density: 0.295


All units are the same as texgen default.
Please let me know what should I do to fix this problem? and if I do not solve the problem what will happen?

[louisepb]

Hi Maryam,

There must be somewhere in your model where the yarn cross-section that you have specified is smaller than the total fibre area. You need to check what cross-sections you have created and check if this is the case. If you have used the refine function then it's possible that the cross-section has been adjusted (and reduced) to avoid intersections. If this is now smaller than the total fibre area it will give the error. You need to find where this occurs and adjust your model accordingly.

Best regards,
Louise

[maryam_sodagar]

Dear Louise

Thanks so much for your clear answer.
you mean when the cross section area is smaller than total fibre area, then this error will arise? and we should edit the geometry to solve this problem and the refine option would not solve the problem?

so when the cross section area is bigger than total fibre area,this error will arise? and by checking refine option it will be solve?

[louisepb]

Hi Maryam,

The first of your statements is correct.
If the total fibre area is greater than the yarn cross-sectional area then the volume fraction will be greater than 1.
The refine option changes the yarn cross-sections to avoid intersections but in the 2D wizard does not check that the changed cross section will still have a volume fraction of less than one.

Hope that helps,
Louise

[maryam_sodagar]

Hi Louise,

Thank you for your reply.
How we can calculate yarn volume?

Packing density= yarn density/fibre density
Volume Fraction= Yarn volume/ Fibre volume

Are they the same as each other? because I know the packing density of my yarns but I do not know how to calculate yarn volume to gain volume fraction

[louisepb]

Hi Maryam,

You can use the functions within TexGen to calculate volume fraction for either the textile or yarn using the GetFibreYarnVolumeFraction functions. Alternatively there are GetYarnVolume functions. Look at the CYarn and CTextile classes here: http://texgen.sourceforge.net/api/names ... x_gen.html

Best regards,
Louise

[maryam_sodagar]

Dear Louise

The unreal volume fraction problem has been solved by changing the geometry.
Thank you so much for this functions but unfortunately as you know I am not familiar enough with these functions to use them.
Would you please tell me step by step what should I write in python console? For yarn resolution you've had told me step by step and that was really helpful.
If it is hard for you, please do not hesitate to tell me you can not.
Thank you so much,

[louisepb]

Hi Maryam,

You can either use textile.GetFibreYarnVolumeFraction() which will give you the yarn volume fraction for the entire textile or yarn.GetFibreYarnVolumeFraction for whichever yarn you're interested in.

If you want the yarn volume you can use textile or yarn.GetYarnVolume() which will give you the volume of the yarn (not taking into account any repeats you may have specified). This will be in m^3 unless you send a string as a parameter specifying different units.

Hope that helps,
Louise

[maryam_sodagar]

Hi Louise

I am so sorry but I need the equation for yarn volume ...as you see in the picture I could not find any equation for calculating the yarn volume...
I really need it now.
I am looking forward to your reply.

vf.jpg (35.38 KiB) Viewed 16536 times

Thank you so much.

[louisepb]

Hi Maryam,

There isn't a simple equation which will give you the yarn volume for your model. You will need to use the functions within TexGen to get the volume of the yarns in your model as described in my previous answer.

Best regards,
Louise

[maryam_sodagar]

Dear Louise

I've got it.

Thank you,

[PhilippV]

Hi Louise,

I’m facing problems getting the right value of the yarn-volume-fraction (yarnvolume/domainvolume) in my script.

I’m able to get the right yarn-volume-fraction when I run the script via TexGen-GUI and use the ‘Quick Calculate Domain Volume Fraction’ - option. But the function Textile.GetQuickDomainVolumeFraction() returns the value zero in my script. Intentionally I haven’t specified any yarn data. So the function obviously doesn’t set the fiber volume fraction of the yarns to 1.

The next thing I tried is to calculate the fraction with the function: Textile.GetYarnVolumePerUnitArea('m')
Also 2 repeat vectors were assigned to each yarn, so that it should return a volume per unit volume. That returned a very small result (...e-7).

I would try to call the two functions CTextile::GetYarnVolume() and CDomain::GetVolume() to calculate the fraction this way, but I don't know how to call the latter function and the GetYarnVolume() doesn't take account of the repeat vectors, recording to the documentation.

Could you help me to call the CDomain::GetVolume() function and/or provide me with another solution to this problem?
My approach to create the domain:

Code: Select all

 # Create and assign domain
domainPlanes = CDomainPlanes(XYZ(DomainPlaneMinX, DomainPlaneMinY, DomainPlaneMinZ), XYZ(DomainPlainMaxX, DomainPlainMaxY, DomainPlainMaxZ))
Textile.AssignDomain(domainPlanes)

Thank you very much in advance for your great and patient support. I’m looking forward to your response.
Philipp

[louisepb]

Hi Philipp,

You've discovered a bug! The reason that the QuickCalculateDomainVolumeFraction function doesn't work from your script will be because the yarn hasn't been built at that point. Although you've specified the yarns etc TexGen doesn't actually interpolate the yarn path and build the surface etc until you call a function which requires these to have been calculated. If you're working in the GUI then this is done in order to render the textile.

I have corrected the function so that it builds the yarn if necessary at the start of the function. This will be available in the next release. Unfortunately 'BuildTextileIfNeeded' is a protected function and not available in the API. As a temporary workround add a line something like
yarn = Textile.GetYarn(0)
This will force the textile to be built and then the domain calculation should work.

Hope that works for you. Let me know if you still have problems.
Best regards,
Louise