Dear Robert,

Yes :), it would be nice if we could easily implement this in sfepy by modifying fibre_function i and creating a new term very similar to FibresActiveTLTerm. I am very new in this field, so could you give me some key starting points on how to do it? 
Another quick question, is, regarding the first term in the expression of active stress which is "viscosity coefficient*strain rate", is what you refer when you said  "creating a new term", and then the exponential term should be introduced by modifying the term_fibers?

Thank you very much!



El viernes, 23 de octubre de 2015, 11:33:27 (UTC+2), Robert Cimrman escribió:
Dear Patricia,

On 10/23/2015 10:39 AM, Patricia Garcia Cañadilla wrote:
> Dear Robert,
>
> I would like to the model the viscoelastic behavior of active fibers, as
> you done in the paper: "Modelling heart tissue using a composite muscle
> model with blood perfusion" or as here:
> http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.488.5795&rep=rep1&type=pdf and
> I was wondering if is easy to implemented in sfepy and/or if there is some
> predefined term in Sfepy, since for example the term "dw_tl_fib_a" doesn't
> include the "exp{k min(0;de/dt}}" that appears in the paper.

The model from the "Modelling heart tissue using a composite muscle model with
blood perfusion" paper would be pretty easy to add, yes. It would involve
modifying fibre_function() in sfepy/terms/terms_fibres.py and creating a new
term very similar to FibresActiveTLTerm. Would you give it a shot? :)

As for the cardiac model, it would certainly be possible to implement those
fibres in sfepy, but not that easy - the model is quite complex. The biggest
issue are the internal unknown variables (the contractile element deformation
epsilon_c), that evolve in quadrature points - those are not supported (yet).

r.