hysteresis model

[nut]

hi Dr.Berstrom,
i have some problems about hysteresis model.I have calculated the parameter from experiment and the problem is C2 value which restrict between(0,-1) but my value is -0.2 and then I put in the hysteresis model in abaqus.The result is it is error in this value.The message noticed that we can use only C2=-1. So I'm so confuse.How can I solve this problem.
The next question,I try to use the creep strain rate patameter that calculate from unixial compression experiment to predict in unixial tension hysteresis model.The result is not good.Can I conclude that the different method give the different parameter.We cannot use the same parameter in different method.
Thank you very much.
Nut

[Jorgen]

Hello Nut,

Here are a few comments:

- Are you using ABAQUS v6.6? The hysteresis model in v6.6 is implemented much better than in earlier versions.

- The value C2=-0.2 seems fine since it is in the rance [-1, 0].

- About tension and compression, what material are you studying? My experience is that the *Hysteresis model (i.e. the Bergstrom-Boyce) model works well in both tension and compression for elastomers.

Jorgen

[nut]

Hi .
My abaqus is version 6.5.It seems to be good in prediction slow rate.I got C2 value =-0.2 .It is error when we put in abaqus.I can use only c2=
-1.What 's wrong? and next is the most important question,I have the example of my experiment.I can calculate parameter,S=1.79.Ua=1.78.Ub=3.19,C1=0.052,C2=-1,m=5.My model is cylinder diameter 25 mm.Height=15mm.I use Neo hook equation to calculate equiliblium curve.Can you show me how to calculate force load and unloading while compress the rubber at 4 mm with strain rate 0.01/s. It is my project and I cannot answer my advisor question how to calculate it.I read many of your paper but i still don't know how to calculate it,How the effective strain rate relate with stress in network B.?

Thank you very much for your answer.
Nut

[Jorgen]

:arrow: ABAQUS v6.5 forces you to use C2 <= -1, whereas ABAQUS v6.6 allows C2 < 0. I recommend that you start using v6.6.

:arrow: Can you provide one or more figures illustrating the results that you get? The stress in Network B is related to the applied deformation rate and the material parameters. You should be able to get good predictions for different strain rates.

- Jorgen

[sq]

Shameless plug:

The best (and most robust) implementation of the Bergstrom-Boyce model for ABAQUS I've come across my organization purchased from Exponent, Inc. I think our contact there was a fellow by the name of Jorgen Bergstrom.