Hyperelastic material model

[Neekoo]

Hi:
I am running a FEA analysis using polyurethane material using ABAQUS and have chosen MARLOW material in ABAQUS to simulate the PEU behaviour. I used stress strain curve from uniaxial tension test.
I was wondering if anyone can suggest other material model e.g. Neo Hookean and if so how can I determine material parameters such as C10, C1 and etc.

Thank you all in advance

 

[koetue]

hi,
you can enter the data from the stress-strain-curve, so that you don't have to obtain the mooney constants. you have to use the card
*uniaxial test data

 

[xerf]

For the Neo-Hookean , C10 is the shear modulus G, while
D is 2/(bulk modulus)..if I remember it well.

 

[prost]

I assume ABAQUS has a Neo Hookean material, since this is a basic hyperelastic material taught in many continuum mechanics courses. If you have uniaxial tests, couldn't you simulate the unaxial test coupons with ABAQUS, use each of the materials MARLOW and Neo-Hookean separately, and compare the ABAQUS simulations with the two materials against the results of the uniaxial tests? Since the deformation is simple enough, you might even be able to compute the analytical solution using the two materials (I know nothing about MARLOW, so couldn't tell you whether it can even be done).

 

[Neekoo]

Hello All:

Thank you so much for your tips. I will run the specimen model as you suggested with Marlow & Neo Hookean and compare the result with uniaxial test.

 

[Neekoo]

Hello All:
Just want to let you know that MARLOW material model, built in ABAQUS follows the stress strain curve and has the closest fit. ABAQUS CAE module has a feature to compare various material model to the test data.
I have another question, how do we define the failure criteria of a ruuber material, if rubber is just in compression stage.
What the von Mises stress should compare against?

Thank you every body

 

[Jordonlaw]

Neekoo,

A better parameter to use for failure analyses would be strain energy density. I've had very good correlation with test data in the past using this.

 

[johnsmith2]

The strain energy criterion is S, developed by George Sih?

 

[gfbotha]

Neekoo

You mentioned the rubber being in compression: If it is confined (under hydrostatic conditions) the Poisson's ratio really needs to be accurate. Under such conditions Von Mises might typically be usefull to evaluate failure (particularly so if it involves a high strain rate).

Or, you might mean it is compressed axially but is free to expand laterally. In which case one could also use max strain to evaluate failure.

By the way, I know about strain energy density being recommended, but could somebody please explain a bit more about how one uses it? Do you compare your FEA result against a "strength"/failure value obtained (indirectly) by first simulating a test coupon up to the point of failure?

Finally, I have seen quite different material behaviour under different types of straining. If you ultimately want to simulate a compression situation, input properties obtained from a simple uniaxial tensile test is likely to lead to significant simulation error (typically softer). So, in case you indeed need more accurate results you might have to consider planar tension (pure shear) and/or equibiaxial and/or compression testing for obtaining your material data.

Gert