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

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

    volTensorField gradDU = fvc::grad(DU);

// gradDU.checkOut();
// gradDU.checkIn();

    Info<< "Reading velocity increment field DV\n" << endl;
    volVectorField DV
    (
        IOobject
        (
            "DV",
            runTime.timeName(),
            mesh,
            IOobject::READ_IF_PRESENT,
            IOobject::AUTO_WRITE
        ),
        mesh,
        dimensionedVector("zero", dimVelocity, vector::zero)
    );

    Info<< "Reading stress increment 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)
    );


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


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

    constitutiveModel rheology(sigma, DU);

    volScalarField rho = rheology.rho();