Arruda-Boyce Neo Ho...
 
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Arruda-Boyce Neo Hookean  


siva634_tn
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Hi everyone,

Is this normal that I get the same deformation values for two simulations (rubber) made with the Neo Hookean and Arruda-Boyce models?

Thanks for your help!

flix

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Jorgen
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The neo-hookean (NH) and Arruda-Boyce eight-chain (EC) model will give the same results if the strains are small.

- Jorgen

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siva634_tn
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(@siva634_tn)
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Thank you for your answer.

I would like to know a little more about what small means in que cases of hyperelastic material.

1. What are the range of strain that we can qualify of small? Is there any specific answer for that?

Now I am working with a strain around 0,4 (uniaxial) ... I imagine this is small compared to some hyperelastic material that can reach something like 800% stretch. I tried almost every fonctions available on Abaqus and I noticed that for this strain, the NH and AB functions get the worst results and they have something like 18% error.

2. Do you think this is acceptable to explain this error by the fact the material gets stiffer as it stretches? Or should I normaly get better results with these models?

flix

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Jorgen
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(1) When talking about the NH and the AB model, small strain is related to the locking stretch parameter. If the applied strain is much smaller than the locking strain then the two models will give the same results.

(2) I dont think that there is a generic answer to that question. Typically the AB model relatively well for large strains and multiaxial loading.

- Jorgen

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Hossein Sahhaf
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Posted by: @jorgen

If the applied strain is much smaller than the locking strain then the two models will give the same results.

Hello dear Mr. Jorgen

What does the "locking strain" means in Hyperelastic model/material?

Thanks, Best Regards.

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Jorgen
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The term "locking strain" is the strain at which the macromolecules in the material (on average) reach their fully extended length. At this point the material becomes much stiffer since the molecules cannot just change configuration, but need to actually stretch. This is an idealized concept that is used in the Arruda-Boyce Eight-Chain hyperelastic model. One of the parameters in this model specifies this max strain/stretch occurs.

-Jorgen

 

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