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Issue with Mooney Rivlin Material

Hi George,

I'm using Mooney Rivlin Material from the literature. My issue is that my material deformation is linear, but it should be non-linear. I'm now starting to mistrust that I set up everything correctly. Is the following correct:

This is the input from the literature:

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

This is my unit-system:

IM2.jpg.103195ab708af9b9deba2f105877b64c.jpg

And this are my material cards:

IM3.jpg.36cc67a87b1d03cb78fac9bd0461460f.jpg

IM4.jpg.cb3ead50e9655f0382175c51a4849666.jpg

What I'm not 100% sure. Is the calculation C1-> mue1 and C2->mue2 correctly done? Are mue1 and mue2 really unit independent?

Best regards,

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Altair Forum User

Hi @jowidmer

Mu1 and Mu2 looks fine (if c1= c10, c2-c01)

Altair Forum User

Do you have a stress-strain curve?

If yes, use LAW 69 directly, instead.

Altair Forum User

Hi Prakash,

Thanks a lot for the reply. Do you have an explanation why I don't get a non-linear angle to moment curve when I bend a block of this material. When you look at the image, this is what someone got with abaqus. On the left side the 2nd curve from the top is with the mue1 and mue2 constants that I showed you here. But in my case when I work with the same constants my disc stays always linear (only stiffness changes).

Best, J

Nachiket Kadu_22143

Hi J

There can be lot many reasons for that to happen i hope BC remains the same you may first check whether in abaqus they included plane shear, bilnear and axial all three of the data and check whether you missed any of this data.

Altair Forum User

@jowidmer

In Abaqus are you using Ogden-Mooney (nonlinear) or just Mooney(Linear)?

Can you share the material and parameters from Abaqus?

Altair Forum User

Hi Nachiket and Kadu

In Abaqus this material was used:

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

It is a a Uanisohyper subroutine. The subroutines (using Yeoh and Mooney-Rivlin materials) are attached as well.

Thanks a lot for your help!

Unable to find an attachment - read this blog

Altair Forum User

Hi @jowidmer

I am checking with experts if there is a similar script in RADIOSS,

Altair Forum User

That would be very nice! Thanks a lot!

Altair Forum User

Hi Prakash,

Do you have any news on the topic?

Best, J

Altair Forum User

Yes, I will share a doc soon with you

Altair Forum User

Cool, thanks!

Altair Forum User

Hi @jowidmer

You can use RADIOSS user subroutine PFA,

Unable to find an attachment - read this blog

Altair Forum User

Hmm, is there a simple way to adapt the files without being expert with user-defined materials? Or is there no way around to work deeply into this topic?

Thanks for your help, Best,

Jonas

Altair Forum User

Hi Jonas,

This is same as Abaqus VUMAT, rest is copy and paste of the FORTRAN script,

Altair Forum User

Hi Prakash,

Hmm.. I tried to go thru the ppt-presentation step-by-step. However, it is quite difficult, since I don't have any background information about what I'm really doing with all these environment variables, and scripts, ect... for example I stuck at slide 28.. how do I generate this dll file? Is there a documentation that shows it a bit more precise?

And could you also explain me the basic principle: Is it correct that I write a user subroutine (using Fortran coding syntax) that has certain input and output variables? I then have to define in my engine file which elements are computed by this subroutine and also have to define the input variables ? The solver than calls at every iteration the subroutine (using the provided subroutine arguments and uses itself the outputs to continue the computation)?