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Relaxation not evident in Abaqus

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Posts: 2
Topic starter
(@harishcherukuri)
New Member
Joined: 16 years ago

Hello,

Im trying to model a viscoelastic material in Abaqus/Standard 6.6.2 and am most interested in rate dependance. Ive created a model using *HYPERELASTIC defintion with Mooney-Rivlin constants, and *VISCOELASTIC using a time domain Prony series derived from constant strain rate uniaxial tension test data.

My model is sized to match the uniaxial tention test specimen, but when I run the model with different loading rates, the results are exactly the same. The rate dependance that should be reflected in the Prony series does not appear. Ive tried running it using both *VISCO and *DYNAMIC.

Is there some keyword that Im missing to alert Abaqus to the fact that this material is viscoelastic? Any help would be greatly appreciated.

- Dan Glanz

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Posts: 3998
(@jorgen)
Member
Joined: 5 years ago

It sounds like you are doing things right. One thing to check is that the applied deformation rate that you are using is within the relaxation times that is specified in the Prony series. If the applied deformation rate is much slower or faster than the Prony series relaxation times then you might get no rate dependence.

-Jorgen

3 Replies
Posts: 2
Topic starter
(@harishcherukuri)
New Member
Joined: 16 years ago

Thanks for the response. The deformation rate is definitely within the bounds of the Prony series Im using.

The odd thing Ive found is that I can get a rate dependance if I use a *STATIC step (which uses the elastic modulus) and then follow it with a *VISCO step, but not if I use a *VISCO step only. It is very strange.

Any thoughts?

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Posts: 3998
(@jorgen)
Member
Joined: 5 years ago

That sounds very strange :confused:

I have never heard of that problem.

Is the inp-file short? Can you post it here?

Thanks,

Jorgen

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