iMechanica - constitutive models - Comments

long-term behaviour

Andreas Burger — Tue, 15 Jul 2008 09:34:04 -0400

Hi Jerry,

I have a few questions regarding your paper:

In my project I'm also interested in the long-term creep/relaxation behaviour of PU. In your proposed const. model you included compression tests with short term strain holding periods (relaxation) to indentify the equilibrium stress-strain response. It is obvious that the material still relaxes after 60 seconds. My question now is can I combine this constitutive model with some sort of "pure" viscoelastic model (coefficients derived from either long-term creep/relaxation experiments or from DMA). Or do you think it is possible to lengthen the 60s holding periods?

Thanks very much for your thoughts on this issue.

Andreas

Almir, Jerry

Andreas Burger — Mon, 14 Jul 2008 10:14:19 -0400

Thanks for the link.

Andreas

Andrea, Thanks for

H Jerry Qi — Wed, 02 Jul 2008 17:22:49 -0400

Andrea,

Thanks for noticing our model.
Although it deals with TPU specifically, it considers the time-dependent and
stretch-induced softening, which are features found in my elastomeric materials.
This also means you can look into other viscoelastoplastic models and find a
proper one for your applications. Of course, you may need to modifiy some
models. You can find a list of papers in the reference of our paper. Good
luck!

Also, www.polymerfem.com is a good resource for polymer FEA modeling.

Jerry

try www.polymerfem.com

Almir Uzunovic — Wed, 02 Jul 2008 05:53:52 -0400

try www.polymerfem.com