# Determination of viscoelastic parameters (Prony or relaxation test data)

Hi all, I need to have my FE model improved with viscoelasticity. I have searched ABAQUS documentation and read some publications, but still have some questions as followed:

1. Polymer samples have been tested in tension with a constant elongation and a 10mins dwell time. This is regarded as one step and stress relaxation repeated many times in the test. Now curves of strain-stress and time-stress are gained, but I have no idea how to get the viscoelastic parameters.

2. Relaxation test data is considered in the beginning since I have done some relaxation tests. I then found there are shear test data and volumetric test data which obviously are not suitable. Maybe Prony should be used and, I should do curve fitting according to the equations of g_i and k_i? In my case the tau_i should be a constant of 10 mins.

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I am new to this topic and really confused with it. Thank you all!

Thank you all!

I recommend that you use the MCalibration license to calibrate a suitable viscoelastic material model. You can download a free trial license here: https://polymerfem.com/free-trial-license/

You should be able to calibrate a basic linear viscoelastic material model to your data.

/Jorgen

Dear Jorgen,

I am trying to convert storage modulus and loss factor to Prony parameters. Do you have any tips?

thank you in advance,

Shabnam

Shabnam,

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I'm not sure I understand your question. The Prony series, for instance a Maxwell model simulating stress relaxation, can be expressed as shown in the image. Normally, you'll have your stress relaxation data, and then you choose a model order for the Prony series, and then you set the G's and tau's to get the model to fit your data.

Regards,

Travis

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