old coupled value on initial

[jessecarterMOOSE]

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Question

How does CoupledValueOld work when initializing materials? I'm using AbaqusUMATStress and passing in a temperature field. The temperature auxvar has an initial condition but CoupledValueOld is 0 which is messing up my material model

[GiudGiud]

Hello

We dont initialize it by default
But if you want to there is a parameter for it
https://mooseframework.inl.gov/source/ics/FunctionIC.html

See the state parameter

Note that this is a local fix, that will work in your input.
But for your code, it would likely be safer not to use the old value on timestep 0

[jessecarterMOOSE]

For the UMAT interface (https://github.com/idaholab/moose/blob/next/modules/solid_mechanics/src/materials/abaqus/AbaqusUMATStress.C) it needs the change in the value as an argument. It's set up to use u - u_old, but since u_old isn't set, I'm getting non-zero values for the incremental change at time zero, which doesn't make much sense.

[jessecarterMOOSE]

@GiudGiud if I use a IC for my AuxVars and specify state = old, will that make coupledValue() == coupledValueOld() at time 0 in my Material?

[GiudGiud]

no it will only set coupledValueOld you ll need another IC to set coupledValue

[jessecarterMOOSE]

So 2 ICs per variable can make the current value and old value the same on startup? I'm okay with that. I can write an action for all my fields

[GiudGiud]

Yes that’s the intent. I have never used that system