Neo-Hook, or other nonlinear model of UHMWPE in Ls-Dyna

[ppalfi]

Dear Dr. Bergstrom and All,

I have to model a mobil bearing knee system. Unfotunately I don't have to much time, only 1 month. We have a license for Ls-Dyna solver, Ansys, and Patran. I'd like to use Ls-Dyna, beacuse I want to create a dynamic model. I was looking for a practicable material model for the bearing, which is a UHMWPE "plate", on the net, but I couldn't find any. I don't have enough time to write a script or any other things, I have to use material models of Ls-Dyna, which are already built in. So please recommend me a model WITH PARAMETERS.

With many thanks:
Peter Palfi
PhD student at BME
www.me.bme.hu

[Jorgen]

Hello Peter,

In your case, where time is more important than accuracy, I suggest that you use a standard elastic-plastic model (I know that LS-DYNA has this). Appropriate material parameters can be found in Table 3 in the following paper (http://www.polymerfem.com/modules.php?name=Downloads&d_op=viewdownloaddetails&lid=6&ttitle=Hybrid_Model1.pdf).

Best of luck,
Jorgen

[ppalfi]

Dear Jorgen,

Thanks a lot, that was my idea. Do you think an elastic-plastic model can be accurate enough, or maybe it would be better to forget my deadline and create a better model?


Thanks a lot again,
Peter

[Jorgen]

That is a good question. It will depend on the details of what you are trying to simulate, how accurate you need the answers to be, and how much time, effort, and resources that you can spend.

There is always a a tough balance between accuracy and cost on one hand, and speed and easy of use on the other.

Jorgen