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PTFE modelling with Abaqus/CAE 6.7-1  

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ang.grim
Posts: 11
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(@ang.grim)
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Dear all,

I am recently trying to run a SINGLE ELEMENT simulation of PTFE with Abaqus and I am facing a problem. If you can help me, I would be really glad.

I have Uniaxial tension experiment data, and I have put this into Test Data Editor (as uniaxial test data). While putting it, I have made some changes in the data since it was saying:

Error in job Job-1: THE NOMINAL STRAINS UNDER THE *UNIAXIAL TEST DATA OPTION MUST BE ARRANGED IN ASCENDING ORDER

Here is my question,

I am running the simulation:

Hyperelastic Material with Marlow strain energy potential ( I think I do not have any other choice since I only have one set of data)

Tensile

100% Displacement

I extract True Stress vs. True Strain data ( Centroid, all elements which is one).

When I compare Stress vs Strain diagrams of experiment and simulation, there is a big difference. I am trying to get the same behavior from experiment.

Could you please suggest me someway or a model to get the same curves?

Regards,

Kara

7 Replies
Jorgen
Posts: 3884
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You dont have to use the Marlow model. You can use any of the hyperelastic material models in Abaqus, or any other model in Abaqus for that matter.

If you are interested in very small strains, then a hyperelastic model is OK. If you are interested in larger strains, then a linear viscoelastic or plasticity model would be better.

-Jorgen

7 Replies
ang.grim
Posts: 11
Topic starter
(@ang.grim)
Active Member
Joined: 12 years ago

Thank you very much Dr. Jorgen.

Now I found my mistake.

Regards,

Kara

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El-Nemr
Posts: 3
(@El-Nemr)
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Joined: 2 years ago

Ive similar issue Im working on. Im analyzing RTV 160 material properties using ABAQUS software and evaluation of material procedure. Ive used only tensile test data. Ive also arranged the nominal stress and strain caluclated values from tensile test in ascending order. I still am having this error.

Error in job Hyperelastic_1: THE NOMINAL STRAINS UNDER THE *UNIAXIAL TEST DATA OPTION MUST BE ARRANGED IN ASCENDING ORDER

can you please help me on how to understand this error?

Thanks
ananths

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Jorgen
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That should not happen if they the nominal strains are arranged in order. An alternative method is to use the MCalibration software to fit the hyperelastic model. The [URL= https://polyumod.com/testing_and_model_calibration/]MCalibration[/URL] software is much more flexible, and for example, does not require the stress values to be in order.

-Jorgen

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El-Nemr
Posts: 3
(@El-Nemr)
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Joined: 2 years ago

Dr Jorgen,

MCalibration software is working great. Thanks for suggesting it. However I also got my Abaqus model to work. However can you help me understand why my D1 and D2 values are 0? (Im using second order polynomial curve fitting). Also, I believe when these values are 0 the system is unstable. Am I right?

Sirija.

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Jorgen
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It is OK for D1 and D2 to be 0. If all D values are zero then the material model is incompressible, which is still OK (just use hybrid elements).

-Jorgen

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