getStatevariable

[rwendner]

How can we get the Statevariableindex inside the material subroutine of MFEM materials?
Is there a method like mat->getHexStateVariableIndex("Imposed Volumetric Strain Increment")?

[zhouxinwei]

Yes.

getHexStateVariableIndex() is method of Material class. All MFEM materials are derived from Material class, so they can use a method from their parent class.

[rwendner]

I tried using getHexStateVariableIndex("Imposed Volumetric Strain Increment") in the subroutine that evaluates the stresses instead of hardcoding the index but got error messages.
Can you please put a working example in the new mfem elastic material?

[zhouxinwei]

Please post the code so we can see how it was used.

[rwendner]

In the following script we need to extract the imposed volumetric strain increment for the stress analysis.
Since all SVs have labels anyway I would like to avoid hardcoding the indices.
This way we optimise the subroutine and only allocate the SVs we actually need, giving them a dynamic index based on the problem at hand.

void mtMElasticUD::calcStrsHx (real *hxv, real *stv) const {
//int iEVSI = type->getHexStateVariableIndex("Imposed Volumetric Strain Increment");
int iEVSI = 13; // in previous version: 7
real hin = lmbDt * (hxv[0] + hxv[1] + hxv[2]) - lmb * stv[iEVSI];
stv[0] += hin + twgDt*hxv[0] - twg * stv[iEVSI] / 3;
stv[1] += hin + twgDt*hxv[1] - twg * stv[iEVSI] / 3;
stv[2] += hin + twgDt*hxv[2] - twg * stv[iEVSI] / 3;
stv[3] += twgDt*hxv[3];
stv[4] += twgDt*hxv[4];
stv[5] += twgDt*hxv[5];
}

[zhouxinwei]

Instead of calling getHexStateVariableIndex() repeatedly, it's better to declare iEVSI as a class member variable, and do "iEVSI = getHexStateVariableIndex("Imposed Volumetric Strain Increment");" in mtMElasticUD::init() to set its value and do some checks. This will also solve the compilation error regarding const method calling a non-const method.

[rwendner]

thanks for the confirmation!
that's what we meanwhile implemented, see gitlab