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Bergstroem Boyce Model - inelastic part


 I was wondering if anyone has experience in implementing the Bergstroem-Boyce Model (Constitutive modeling of the time-dependent and cyclic loading of elastimers and application to soft biological tissue, 2001)? I am struggling with the implementation of the viscoplastic part (Network B) of the model:

I’m not really sure at the moment how to implement the stress.  I
understand that you can decompose the deformation gradient F into an elastic and
plastic component.  In the stress formulation they use the elastic part  of F (Eq 2)
to get dev(Be*) and Je.  From all these equations I am not sure how to get Fe
and Fp.  I tried to go backward starting with the effective strain rate (Eq 3).
 However, the rate uses the plastic effective stretch, which is based on the
plastic Bp*, which in term comes from Fp… I understand that the effective strain
rate is an important part of these kinds of models.  

Basically the only thing
known at the beginning of the step is F=FA=FB=Fe=Fp=1.  I’ve tried to find
references/books that explain similar procedures, but couldn’t. 

 Is anyone aware of a describtion of the implementation of a this or a similar model?




karelmatous's picture

This paper might help:

Finite element formulation for modeling nonlinear viscoelastic elastomers

Computer Methods in Applied Mechanics and Engineering

Volume 197, Issues 51-52, 15 October 2008, Pages 4702-4717 


Amit Acharya's picture

Thanks a lot for the input



Hüsnü Dal's picture

Hi Andreas,

There is an implementation presented at ECCMR, 2007 in Paris.

This might help. This implementation is released in the new version of ANSYS also.

I do not now, how to embed *pdf files to the messages, but I can provide you the *pdf file if you write to me.




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