[mkraposhin]

Dear Foamers, after inspecting solvers like solidDisplacementFoam (and similar) i found, that increase of pressure on surface leads to expansion of material!

This error have roots in patch description: surface normal pressure is added to traction (but it must be subtracted), let's see to tractionDisplacementFvPatchVectorField.C

    gradient() =
    (
        (traction_ + pressure_*n)/rho
      + twoMuLambda*fvPatchField<vector>::snGrad() - (n & sigmaD)
    )/twoMuLambda;

But it must be:

    gradient() =
    (
        (traction_ - pressure_*n)/rho
      + twoMuLambda*fvPatchField<vector>::snGrad() - (n & sigmaD)
    )/twoMuLambda;

I think, that this error must be eliminated in next versions

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And of course, excuse me my English