Prony series in Ls-Dyna

[bebba]

Hi,
I have a problem related to switching the prony series coefficients from an Abaqus input file into an LS-Dyna input file. My idea is that in Ls-Dyna the Gi coefficients are not adimensional (as for Abaqus) and moreover the G(infinite) term is missing. Is it correct? Does anybody know how to mange this problem?
Thank You

Mercuzio

[Jorgen]

I'm assuming that you are referring to *Mat_General_Viscoelastic. As you noticed, this LS-DYNA model defined the Prony series slightly different than what ABAQUS is using.

The LS-DYNA Gi coefficients have a dimension of stress.
In order to set the G(infinite) term you can set one beta_m term to be zero.

It should be possible to get the same effective model by using the appropriate set of material parameters.

- Jorgen

[bebba]

Thank you very much for your help, it was really usefull.
Ciao
Mercuzio

[luckboat]

hi,
I have a problem in finding the parament of concrete_damage. I can only konw a little. please help me .
thank you advanced.
my email is: 272974158@qq.com

[Jorgen]

What FE software do you use?

[luckboat]

What FE software do you use?

I use Ansys ls-dyna.and i need concrete_damage parament.
thank you very much

[Jorgen]

What LS-DYNA material model ID is that?
Do you have experimental data to use for the calibration?

[hsadeghi]

Dear Dr Jorgen,

I'm using LS-DYNA and I'm trying to use MAT_006 to model dissipation in PMMA. I have dynamic frequency data (storage and loss modulus) and I'm trying to find G_infinity G_0 and beta required by LS-DYNA. I read your note titled "Calculation of Prony Series Parameters From Dynamic Frequency Data" but there is still points that is not clear to me:
-It seems that the formulation for G(t) is slightly different in your note. How does g_i relate to G_infinity?
-In the algorithm at the end of the note at step 5 what function do we minimize?
-To do this algorithm is it possible to do it at just 1 frequency or I should have experimental data at several frequencies?
-Is there any references that provides more detail for this?

Thanks,
Hossein

[happypearl]

What LS-DYNA material model ID is that?
Do you have experimental data to use for the calibration?

Dear Dr Jorgen,
Recently, I'm using LS-Dyna with *mat_158 to simulate the dynamic characteristics of woven fabrics. And now all the experimental data I have is the stress-strain curve under different strain rates. In mat_158, prony series is used to simulate the strain dependent of the material. But I have no idea on how to derive the prony parameters with the existing data. Besides, I have read all your reply in forum viscoelascity and still couldn't get the point. So can you please spare some time to explain the detaied procedure?
I'd appreciate that.
Shi

[Jorgen]

I would use MCalibration to solve that problem.

-Jorgen