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# bergstrom_boyce jmps 1998

Posts: 3
Topic starter
(@andreasa)
New Member
Joined: 13 years ago

Hi everyone

im looking for an apropriate model for silicone rubber and came across

the berstrom boyce model in jmps from 1998.

when looking at the paper i found someting that was not quite clear to me

and i hope someone here can help me with this. the modle consists of two

networks, A and B, where only network B can bevelop inelastic deformation.

now looking at the evolution law for network B the shear rate, given by

(24), is given by something like

gamma_dot = C1_hat * (\lambda^{Bp}_{chain} - 1)^C2 * tau

to me (and i guess that im wrong here) this looks funny becaurce

starting of with Fp = I gives \lambda = 1. this means that the expresion found within the parathesis above would be zero i.e. gamma_dot would be

zeros what ever value the stress tau takes.

can someone pleas give me a hint here since i guess im not getting this right.

best

magnus

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Posts: 3941
Moderator
(@jorgen)
Member
Joined: 2 years ago

The Bergstrom-Boyce (BB) model is an excellent choice for silicone rubber.

The flow equation is still OK since lambda^Bp is only 1 in the undeformed initial state, and in this state tau=0 as well.

To make this point clearer, however, I proposed a modification to the flow equation in a later [URL= https://polymerfem.com/forums/showthread.php?t=2 ]paper[/URL].

-Jorgen

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2 Replies
Posts: 3
Topic starter
(@andreasa)
New Member
Joined: 13 years ago

thanks a lot.

i will have a look at the modified version of bb-model!

best ragards

magnus

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