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# Visco-elastic model in ABAQUS

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(@prathyusha430)
New Member
Joined: 11 years ago

Hi,

I am trying to model the Brain material properties from literature,

I have to following data:

Density

Bulk Modulus K (GPa)

Short Term Shear Modulus G(0) (Pa)

Long Term Shear Modulus G(inf.) (Pa)

Decay Constant (&#946,) (s[SUP]-1[/SUP])

the paper says it uses the following formula:

G(t) = G&#8734, + (G0 G&#8734, )e[SUP]&#946,t[/SUP]

does anyone know how I can model this behavior in ABAQUS?

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Posts: 2
(@Mahsa)
New Member
Joined: 12 years ago

Hello,

I have no experience in modelling such material. Also I am not familiar with the formula you have stated, but it looks like a form of stress relaxation or creep definition.
I will try to explain how I would model your case, but please note, that I am as well learning how to model hyper-visco response.

[B]Density [/B]- could be explicitly defined for a model

[B]Short term shear modulus[/B] - could be used as an input to neo-hookean hyperelastic model, where the constant is G/3 (not sure about that, but you could probably look for it on google)
- If short term means instantaneous response, make sure you select this option on neo-hookean model in abaqus

[B]Long term shear modulus[/B] - I would compare it to the short term one and then use this for aproximation of stress-relaxation test data
Example:
short term = 30, long term = 15 -> this will result in a stress relaxation data leadingsomething like this:

time coef
0 1
1000 0.5

(the 1000 is the infinite time and 0.5 is the proportion of long term to short term G)

[B]Decay[/B] - no idea

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Posts: 83
(@zhaiys)
Trusted Member
Joined: 16 years ago

I havent used this... but, theres a Prony series viscoelastic model in ABAQUS, if I am not mistaken. You should be able to specify the shear relaxation modulus in ABAQUS so that it follows your (Voce-hardening) expression.

What youre describing sounds like a textbook situation. Almost makes me want to bring out a handbook on Laplace transforms. ðŸ™‚

Mats

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