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Problem with PRF and *steadystatedynamics and *visco in Abaqus  


gabrielnc
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(@gabrielnc)
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Hi I'm trying to simulate a DMA test analysis but I've encountered a big issue. I want to know if it is possible to use Nonlinear viscoelasticity in an *steadystatedynamics,direct step or in a *Visco Step. If I use any of the mentioned steps with linear viscoelasticity (prony) I obtain similar results both in time and frequency domain. The material shows a viscoelastic behavior. But if I use a PRF model (law=strain) the material does not shows any viscoelastic phenomena. In other words using PRF the Loss modulus of the materials shows a value of zero (imaginary part of stress in SSD analysis = 0). In the file (please change the extension from .pdf to .zip) attached you will find the two approaches of analysis (*visco and *steadystate) and the input of the material properties. Thank you in advance

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Jorgen
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The PRF model should work with *VISCO. I have used many different versions of the PRF model that way, and it does dissipate energy.

I don't recall if the PRF model works with *SteadyStateDynamics. I ran your test case using Abaqus 2019, and I get the warning:

***WARNING: VISCOELASTIC MATERIAL PROPERTIES ARE DEFINED IN THE MODEL. THE MATERIAL RESPONSE IN A STATIC ANALYSIS WILL BE BASED ON THE INSTANTANEOUS ELASTIC MATERIAL PROPERTIES.

Suggesting that it probably does not work (not surprising).

I also noticed that your material model contains an exceptionally many networks (20), and that the Sratio for about half the number of networks is basically 0. I would get rid of those networks.

-Jorgen

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gabrielnc
(@gabrielnc)
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@jorgen

Thank you Jorgen for your response! 

I tried with my material and others from the documentation and the results are the same. 

If I use *visco step I don't have dissipation, stress and strain are in the same phase. 

I've delete the networks with sr=0 as you suggested. 

Attached are the inp files (change .pdf by .zip)

 

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