# Rank Four Aux

Access a component of a RankFourTensor

## Description

The AuxKernel RankFourAux is used to save single components of Rank-4 tensors into an AuxVariable for visualization and/or post-processing purposes, similar to the functionality provided by RankTwoAux for Rank-2 tensors RankFourAux is commonly used to output components of the elasticity (or stiffness) tensor, , in mechanics simulations.

The RankFourAux takes as arguments the values of the index_i, index_j, index_k, and index_l for the single Rank-4 tensor component to save into an AuxVariable. (1) Eq. 1 shows the index values for a linear hyperelastic stiffness tensor with 21 indepent material parameters; the various available elasticity tensor symmetry options is discussed in the material ComputeElasticityTensor documentation.

## Example Input File Syntax


[./matl_C25]
type = RankFourAux
rank_four_tensor = elasticity_tensor
index_i = 1
index_j = 1
index_k = 0
index_l = 2
variable = C25
[../]
(moose/modules/combined/test/tests/linear_elasticity/tensor.i)

An AuxVariable is required to store the RankFourAux AuxKernel information. Note that the name of the AuxVariable is used as the argument for the variable input parameter in the RankFourAux block.


[./C25]
order = CONSTANT
family = MONOMIAL
[../]
(moose/modules/combined/test/tests/linear_elasticity/tensor.i)

## Input Parameters

• rank_four_tensorThe rank four material tensor name

C++ Type:MaterialPropertyName

Description:The rank four material tensor name

• index_lThe index l of ijkl for the tensor to output (0, 1, 2)

C++ Type:unsigned int

Description:The index l of ijkl for the tensor to output (0, 1, 2)

• index_jThe index j of ijkl for the tensor to output (0, 1, 2)

C++ Type:unsigned int

Description:The index j of ijkl for the tensor to output (0, 1, 2)

• index_kThe index k of ijkl for the tensor to output (0, 1, 2)

C++ Type:unsigned int

Description:The index k of ijkl for the tensor to output (0, 1, 2)

• index_iThe index i of ijkl for the tensor to output (0, 1, 2)

C++ Type:unsigned int

Description:The index i of ijkl for the tensor to output (0, 1, 2)

• variableThe name of the variable that this object applies to

C++ Type:AuxVariableName

Description:The name of the variable that this object applies to

### Required Parameters

• execute_onLINEARThe list of flag(s) indicating when this object should be executed, the available options include NONE, INITIAL, LINEAR, NONLINEAR, TIMESTEP_END, TIMESTEP_BEGIN, FINAL, CUSTOM.

Default:LINEAR

C++ Type:ExecFlagEnum

Description:The list of flag(s) indicating when this object should be executed, the available options include NONE, INITIAL, LINEAR, NONLINEAR, TIMESTEP_END, TIMESTEP_BEGIN, FINAL, CUSTOM.

• boundaryThe list of boundary IDs from the mesh where this boundary condition applies

C++ Type:std::vector

Description:The list of boundary IDs from the mesh where this boundary condition applies

• blockThe list of block ids (SubdomainID) that this object will be applied

C++ Type:std::vector

Description:The list of block ids (SubdomainID) that this object will be applied

### Optional Parameters

• control_tagsAdds user-defined labels for accessing object parameters via control logic.

C++ Type:std::vector

Description:Adds user-defined labels for accessing object parameters via control logic.

• enableTrueSet the enabled status of the MooseObject.

Default:True

C++ Type:bool

Description:Set the enabled status of the MooseObject.

• seed0The seed for the master random number generator

Default:0

C++ Type:unsigned int

Description:The seed for the master random number generator

• use_displaced_meshFalseWhether or not this object should use the displaced mesh for computation. Note that in the case this is true but no displacements are provided in the Mesh block the undisplaced mesh will still be used.

Default:False

C++ Type:bool

Description:Whether or not this object should use the displaced mesh for computation. Note that in the case this is true but no displacements are provided in the Mesh block the undisplaced mesh will still be used.