Novice in FEA for viscoelastic and hyperelastic materials

[bhaldal]

Ok, I am a real starter in FEA for viscoelastic and hyperelastic materials. So, please pardon my stupidity.

The questions that keep on bugging me when I compare these types of materials with regular linear elastic materials:
- Is there a defined yield point for hyperelastic and viscoelastic materials? I presume that this is somehow related to elongation ratio for hyperelastic materials (elongation before break --> elongation stress?). How does that translate into say Von Mises type of condition? what is the analogue for viscoelastic material failures?
- I suppose this has got something to do with strain energy density function (SEDF). The derivative with respect to deformation sensor of the SEDF should give stress distribution. Does that also give failure criterion?
- How does one choose timescale for hyperelastic and viscoelastic materials for simulations?

Your help on this forum would mean a lot. Also, please suggest tutorials and books that can directly correlate FEA and theory (and not just independent books, if possible).
Thanks Much,

Bhal

[Jorgen]

1) There is no yield point for hyperelastic material model
2) I think most people would say that a linear viscoelastic material does not have a yield point either. Yielding is the onset of permanent deformation and requires some form of plastic deformation.
3) Failure is not given by a strain energy density.
4) The time scale does not matter for hyperelastic materials
5) The time scale needs to be correct for viscoelastic materials. The "correct" time is typically the real physical time.

-Jorgen