Use_displaced_mesh in StressDivergenceTensors (TensorMechanics)

[Srinath Chakravarthy]

I am MOOSE newbie and i am trying to understand "use_displaced_mesh" and "finite_deform_jacobian" in the TensorMechanics module. According to the code, use_displaced_mesh is never used in the Divergence calculations. Has this option been superseded by finite_deform_jacobian ?? Can someone explain this 

[Stephanie Pitts]

Srinath,

See the discussion on when to use the `use_displaced_mesh` parameter in the overview to stress divergence documentation here ( http://www.mooseframework.org/moose/modules/tensor_mechanics/StressDivergence.html ) and the documentation for the stress divergence kernel for information about the `finite_deform_jacobian` ( http://www.mooseframework.org/moose/source/kernels/StressDivergenceTensors.html ).

Hope this helps,

Stephanie

On Wed, Jul 18, 2018, 13:06 Srinath Chakravarthy <srin...@gmail.com> wrote:

I am MOOSE newbie and i am trying to understand "use_displaced_mesh" and "finite_deform_jacobian" in the TensorMechanics module. According to the code, use_displaced_mesh is never used in the Divergence calculations. Has this option been superseded by finite_deform_jacobian ?? Can someone explain this 

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[Srinath Chakravarthy]

Stephanie,

Thanks for the info. I think I understand it now. I am attempting to write an application with coupled electro-chemo-mechanics based on a recently developed model. Consquently I need to use a slightly different kernel than the standard stress divergence kernel in moose. It would be nice to do this in a total lagrangian since getting the appropriate incremental co-rotational jacobians is a pain. 

Any suggestions on how to do so ?

I have already started on this and was wondering the following 

1) the grad_disp also computed on deformed coordinates when using use_deformed_mesh

2) In what locations do I need to specify use_deformed_coordinates to mimic the master action. 

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[Stephanie Pitts]

Srinath,

We do not have total Lagrangian formulation in tensor mechanics, although, as the MOOSE developers say, we're happy to take pull requests to expand MOOSE and tensor mechanics. We have an incremental Lagrangian formulation in the crystal plasticity code of the tensor mechanics module (https://github.com/idaholab/moose/blob/devel/modules/tensor_mechanics/src/materials/FiniteStrainUObasedCP.C) which may be of some help to you.

I'm not sure about the use_deformed_mesh and use_deformed_coordinates options. The use_displaced_mesh option will indeed influence which mesh is used to calculate the gradients of the shape functions; these shape functions are used to calculate the gradient of the nodal variable (displacements in tensor mechanics).

Would one of the MOOSE developers more familiar with libmesh and the mesh information available in MOOSE help answer these questions please?

 > 1) the grad_disp also computed on deformed coordinates when using use_deformed_mesh
> 2) In what locations do I need to specify use_deformed_coordinates to mimic the master action.

Stephanie

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