Modeling viscoelastic material in ABAQUS

[khoo0030]

Hi all,

I understand that to model viscoelastic material in ABAQUS requires storage modulus and loss modulus for shear (g*)and bulk modulus (k*).

The material data that i have is in nomograph format and gives the shear (storage) modulus (in MPa) and loss factor. i assume that the material is incompressible.

I am thinking of modeling the viscoelastic in frequency domain using the tabular method.

real g = G(l) / G(infinite)
Im g = 1 - G(s) / G(infinite)

I am confused if the shear storage modulus given in the data is G(s) and how do i determine G(l) and G(infinite) from the data?

Any help is much appreciated! Thanks!

[Jorgen]

I am not quite sure I understand the terms that you are using in your question. Can you explain more?

[khoo0030]

I am trying to model viscoelastic material in ABAQUS using Tabular frequency dependence.

From the help file, it states that the parameters required are shear modulus (g*) and bulk modulus (k*).
Assuming that the material is incompressible, i can ignore bulk modulus.

In ABAQUS, i need to input (omega g* real) and (omega g* imag)

omega g* real = G(l) / G(infinity)
omega g* imag = 1 - G(s)/G(infinity), where

G(l) is loss moduli
G(s) is storage moduli
G(infinity) is long term shear moduli

My question is that the material data i have gives the shear storage modulus and the loss factor. I am unsure if the G(s) can be directly taken from the data since g* to G involves a complex fourier transform. And also how do i determine G(infinity).

Hope this helps to explain better.

[Jorgen]

I would think that since tan(delta) = G'' / G' is valid for each frequency, you can obtain G(s) directly from your data.

The long-term shear modulus is approach in the limit at the freq goes to zero. It can also be determined from static stress-strain data.

- Jorgen

[pateno]

I don't see why you're involving the Fourrier transform as you gave us the formulas that relate g* and G:
omega g* real = G(l) / G(infinity)
omega g* imag = 1 - G(s)/G(infinity)

Does that mean you have data in the frequency regime and you want first to convert them as a function of time?
Typically (freq-temp) data are obtained via DMA experiments (which gives you the complex modulus, which make me think you have DMA data), whereas time relaxation modulus functions are obtained via creep experiments (lone storage modulus).

Concerning the G(infinity) it is equivalent as the storage modulus in the rubbery plateau. Using rheological simplicity, it's the value for high temperature or low frequency.

Hope this input will help.

pateno