plotting Hyperelastic material property 1

[aminjamali]

I am doing some analyses on Hyperelstic materials. I was wondering how to plot the hyperelastic material (stress vs. strain) curve? Thanks a lot for your help.

 

[qwicker]

Typically, you want to have test data available for most models. Since you say you have stress/strain curve, I presume this if for a uniaxial pull? In any case, when you go to the material properties there is a model called curve fit. It will ask for your data in raw format (reads txt files). You can input as much data as you have. Then you can select different material models to fit to your test data. It will calibrate the models and fill in all those weird constants that the hyperelastic models have. Hope that helps.

 

[aminjamali]

Hi qwicker,

Well I don't have any stress-strain data. Actually I was studying problem VM56 of ansys help (Verification Manual of Ansys V11): "Hyperelastic Thick Cylinder Under Internal Pressure".
The rubber is modeled using 1) Linear Isotropic (When i click on it, it gives me nothing but a warning) and 2) Mooney-Rivlin (2 parameter).
I thought these are enough to be as the properties of the rubber. So one should be able to plot this material. I was wondering how can I do that?

Thanks for your help

 

[qwicker]

Hmm well I have noticed that alot of times the Ansys examples "skip" some general knowledge. For example, I assume it told you what the parameters were for the Mooney-Rivlin model. However, who knows what material they are from or how they were determined. Unfortuantely, it is my feeling that you cannot just plug and chug for hyperelastic materials. For my company, when doing analysis with rubber, we send test samples to a test company which does a whole world of tests on them (uniaxial, biaxial, shear, compression) for about $2000 per sample. Then I can input all that data into ansys and Ansys will solve for the parameters of say Mooney-Rivlin, or Ogden, Yeoh, etc.

I can't just tell you what values to use for rubber. It is alot more complex than you probable realize (It took me a while to understand the complexities as well).

Hope that info helps!

 

[aminjamali]

Your information helps a lot! Thank you very much.

Amin

 

[qwicker]

Glad to be of service!