Learning Forum

[Yspartan]

[peteroznewman]

Array
The incompressibility parameter D1 = 2/K where K = Bulk Modulus.
/forum/discussion/4867/calculating-incompressibility-parameter-for-ogden-material-model

[Yspartan]

Array Thank you for your reply. I am using Mooney Rvlin 5 parameter, and this is the material https://docs.carbon3d.com/files/technical-data-sheets/tds_103208-00-e_epu-40.pdf . Will the equation you mentioned above will still work for Mooney Rvlin? Also what exactly is incompressibility factor? Tried to research online couldn't find a satisfying explanation. As you might see the only available properties for this material are elongation and corresponding stress values. However, in an impact test the material will undergo sudden compression. Do you believe these properties can be used still for the impact test ? I am inputting them in uniaxial test data for the material and then applying Mooney rvlin. If you want I can attach a zip of my simple setup.
Regards
Y.S

[peteroznewman]

Array
Yes, the equation is the same. Here is the Wiki page on Bulk Modulus. https://en.wikipedia.org/wiki/Bulk_modulus
I see in the pdf file you link to there is a Stress-Strain curve for a Tensile Test. You could digitize that data and use it in curve fitting for Money Rivlin.

[peteroznewman]

Array
Yes, that is the same equation for Money-Rivlin. Here is the Wikipedia entry... https://en.wikipedia.org/wiki/Bulk_modulus
In the PDF link is a graph of the uniaxial test data. You can digitize that graph and do some curve fitting in the material model to come up with coefficients for the material model.
It would be ideal if your simulation involves compression to get compression test data, but if all you have is uniaxial tensile data, that is all you have.
Materials behave differently at high strain rates that are found in impact events. Ideally, you would get rate dependent material properties, but if all you have is quasi-static material properties, that is all you have.
It really comes down to how important is the event you have to simulate and what resources you can bring to bear on the problem. If your resources are limited and the event is not too critical, then you use what you have. If you have the time and money to get proper material test data and the event you are trying to simulate is critical, then you get the proper test data.

[Yspartan]

.

Thanks peteroznewman for this insight.

.