Temperature dependent BB Model

[chhapadia]

Incorporating temperature dependence for the Bergstrom Boyce requires that the hyperelastic and the flow equations be modified.

Can anybody help me with the modified equations for my UMAT? Also what other changes are necessary for the code to give a good response for high temperature uniaxial loading tests.

[Jorgen]

Good question. I guess I did not publish how that can be done.

The easiest and likely most appropriate way to add temperature dependence is to:
1) make the hyperelastic shear modulus temperature dependent
2) make the flow resistance (which I often call tauBase) temperature dependent.

If the range of temperatures that you want to capture is small then you may be able to simply use a linear temperature dependence.

-Jorgen

[chhapadia]

My temperature variation ranges from -1C to 160C. Also I would like to get some more information on how to modify the governing equations in the UMAT. Which all equations should be changed. My input constants are in the form of ('98 & '01) paper (i.e) Cr(A), Cr(B), N(A), N(B),k,C1,C2,m.

[Jorgen]

I would make the following changes:

muA = function of temperature (to be experimentally determined for your material)

muB = constant time muA

tauBase = function of temperature (to be experimentally determined for your material)


Best of luck,
Jorgen

[chhapadia]

Does that mean all other constants are temperature invariant? Also the range of variation in temperature is too high. What care should be taken foe that.

[Jorgen]

I suggest that you start with the simple temperature dependence that I outlined. If that turns out not to be sufficient for your material then you can add more temperature dependencies.

-Jorgen