foam-extend4.1-coherent-io/applications/solvers/solidMechanics/elasticPlasticNonLinULSolidFoam/createFields.H

    Info<< "Reading incremental displacement field DU\n" << endl;
    volVectorField DU
    (
        IOobject
        (
            "DU",
            runTime.timeName(),
            mesh,
            IOobject::MUST_READ,
            IOobject::AUTO_WRITE
        ),
        mesh
    );

    volTensorField gradDU = fvc::grad(DU);

    Info<< "Reading accumulated displacement field U\n" << endl;
    volVectorField U
    (
        IOobject
        (
            "U",
            runTime.timeName(),
            mesh,
            IOobject::READ_IF_PRESENT,
            IOobject::AUTO_WRITE
        ),
        mesh,
        dimensionedVector("zero", dimLength, vector::zero)
    );

    Info << "Reading accumulated strain field epsilon\n" << endl;
    volSymmTensorField epsilon
    (
        IOobject
        (
            "epsilon",
            runTime.timeName(),
            mesh,
            IOobject::READ_IF_PRESENT,
            IOobject::AUTO_WRITE
        ),
        mesh,
        dimensionedSymmTensor("zero", dimless, symmTensor::zero)
    );

    // total plastic strain
    volSymmTensorField epsilonP
    (
        IOobject
        (
            "epsilonP",
            runTime.timeName(),
            mesh,
            IOobject::READ_IF_PRESENT,
            IOobject::AUTO_WRITE
        ),
        mesh,
        dimensionedSymmTensor("zero", dimless, symmTensor::zero)
    );

    volSymmTensorField DEpsilon
    (
        IOobject
        (
            "DEpsilon",
            runTime.timeName(),
            mesh,
            IOobject::READ_IF_PRESENT,
            IOobject::AUTO_WRITE
        ),
        mesh,
        dimensionedSymmTensor("zero", dimless, symmTensor::zero)
    );

    Info << "Reading accumulated stress field sigma\n" << endl;
    volSymmTensorField sigma
    (
        IOobject
        (
            "sigma",
            runTime.timeName(),
            mesh,
            IOobject::READ_IF_PRESENT,
            IOobject::AUTO_WRITE
        ),
        mesh,
        dimensionedSymmTensor("zero", dimForce/dimArea, symmTensor::zero)
    );


    Info << "Reading incremental stress field DSigma\n" << endl;
    volSymmTensorField DSigma
    (
        IOobject
        (
            "DSigma",
            runTime.timeName(),
            mesh,
            IOobject::READ_IF_PRESENT,
            IOobject::AUTO_WRITE
        ),
        mesh,
        dimensionedSymmTensor("zero", dimForce/dimArea, symmTensor::zero)
    );

    //- explicit terms in the momentum equation
    volVectorField divDSigmaExp
    (
     IOobject
     (
      "divDSigmaExp",
      runTime.timeName(),
      mesh,
      IOobject::NO_READ,
      IOobject::NO_WRITE
      ),
     mesh,
      dimensionedVector("zero", dimensionSet(1, -2, -2, 0, 0, 0, 0), vector::zero)
     );

      volVectorField divDSigmaNonLinExp
      (
        IOobject
        (
     "divDSigmaNonLinExp",
     runTime.timeName(),
     mesh,
     IOobject::NO_READ,
     IOobject::NO_WRITE
     ),
        mesh,
        dimensionedVector("zero", dimensionSet(1,-2,-2,0,0,0,0), vector::zero)
       );

    constitutiveModel rheology(sigma, DU);

    volScalarField rho = rheology.rho();

    volScalarField mu = rheology.mu();
    volScalarField lambda = rheology.lambda();
    surfaceScalarField muf = fvc::interpolate(rheology.mu());
    surfaceScalarField lambdaf = fvc::interpolate(rheology.lambda());

    surfaceVectorField n = mesh.Sf()/mesh.magSf();

   // plastic strain increment
   const volSymmTensorField& DEpsilonP = rheology.DEpsilonP();

   // for aitken relaxation
   volVectorField aitkenDelta
   (
        IOobject
        (
     "aitkenDelta",
     runTime.timeName(),
     mesh,
     IOobject::NO_READ,
     IOobject::NO_WRITE
     ),
        mesh,
        dimensionedVector("zero", dimLength, vector::zero)
    );
// aitken relaxation factor
scalar aitkenInitialRes = 1.0;
scalar aitkenTheta = 0.1;

//    volVectorField resid
//    (
//         IOobject
//         (
//      "resid",
//      runTime.timeName(),
//      mesh,
//      IOobject::NO_READ,
//      IOobject::AUTO_WRITE
//      ),
//         mesh,
//         dimensionedVector("zero", dimless, vector::zero)
//     );