# Modeling linear viscoelastic solid in abaqus

Hello Experts!

I am a beginner in Abaqus as well as Viscoelastic materials. So my question may sound like a very basic or rookie question.

I am trying to model a viscoelastic material which has one linear elastic soring with G1 and a spring in parallel with a dashpot, G2 and Viscosity, eta .

A value of Tau(s) = eta /(G1+G2) = 0.99 s

Other available parameters-

Time independent bulk modulus K

Time dependent Youngs modulus E(0) and E(inf)

And Poisson ratio nu(0) and nu(inf) are available.

I am trying to develop this model in an attempt to simulate nanoindentation process.

First attempt made was with abaqus Prony series parameters,

g_i , k_i and Tau_i by using single set of values as follow-up

g_i = G1/(G1+G2) = 0.099, since g_i are normalized values

k_i = 0.99, K is time independent, but abaqus wont take values >= 1

Tau_i = 0.99 s, used as available

Used E(0) and nu(0) for initial deformations.

I got a set of results which dont seem reliable.

I think I have gone wrong with those parameters.

How should I calculate these parameters? Any other method than Prony series?

It sounds like you are doing it about right. If you have problems making it behave as expected, then I would do it the other way around. Select the linear viscoelastic parameters and see how the model will respond.

You should consider trying the [URL= https://polymerfem.com/articles/material-model-calibration ]MCalibration [/URL]software. It is excellent that working with viscoelastic material models.

-Jorgen

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