HNBR material model vs technical datas

[Stephane_P]

Hello everybody,

Let me introduce myself, I am Stephane, French student in mechanical engineering school, especially for FEA subjects. I am currently in work placement in a company, performing some ANSYS FEA calculations. For one of this study, I have a rubber washer to define. It must be in HNBR material for some heating reason. It only works in compression.

I have some technical datas from providers, very often they are :
- Hardness (Shore A)
- Tensile strenght
- Ultimate elongation
- Modulus 100% (compression set)

I thinked to modelize this material by using "classical" elastomer model such Neo-Hookean or simplier Blatz-Ko (considering material is incompressive)

My questions are :
- What about the choice of this model ? May I consider Mooney-Rivlin instead of the one I chose ?
- Is my technical datas enough to define this material model ? In fact, is there a relation between Hardness, Tensile Strenght, Ultimate elongation, compression set and Bulk, shear or Young modulus ? Since providers never give these values.

I hope someone will be able to answer, don't hesitate to ask if something is not clear in my demand.

(sorry for my English, I think it is far away from perfection)

[Jorgen]

If you do not need very accurate FE predictions then a simple neo-hookean material model is fine. You can estimate the two neo-hookean material parameters (shear and bulk modulus) from the data that you mentioned, but it would be more accurate to experimentally test the material to find out the real properties.

-Jorgen

[Stephane_P]

If you do not need very accurate FE predictions then a simple neo-hookean material model is fine. You can estimate the two neo-hookean material parameters (shear and bulk modulus) from the data that you mentioned, but it would be more accurate to experimentally test the material to find out the real properties.

-Jorgen

Thank you for your answer.

For the moment I don't need very accurate model, I just need to have a correct estimation of load to apply to obtain some displacement.

Can you precise me how to obtain shear and bulk modulus with the data I have ? I did not manage to find any relationship... I have just just find relationships with shear / bulk / young / poisson ratio, but no one with Tensile strenght, elongation or Hardness...

Thank you one more time for your kind help.

[Jorgen]

You can assume that the bulk modulus is about 500 times higher than the shear modulus.

There are relationships between hardness and modulus, see for example the following thread.

-Jorgen