Stress Divergence RZ Tensors

Calculate stress divergence for an axisymmetric problem in cylindrical coordinates.

Description

The kernel StressDivergenceRZTensors solves the stress divergence equation for an Axisymmetric problem in the cylindrical coordinate system on a 2D mesh.

The axis of symmetry must lie along the -axis in a or cylindrical coordinate system. This symmetry orientation is required for the calculation of the residual and of the jacobian, as defined in Eq. (4).

The StressDivergenceRZTensors kernel can be automatically created with the TensorMechanics Master Action. Use of the tensor mechanics master action is recommended to ensure the consistent setting of the use_displaced_mesh parameter for the strain formulation selected. For a detailed explanation of the settings for _use_displaced_mesh_ in mechanics problems and the TensorMechanics Master Action usage, see the Introduction/Stress Divergence page.

Residual Calculation

The stress divergence kernel handles the calculation of the residual, , from the governing equation and the calculation of the Jacobian. From the strong form of the governing equation for mechanics, neglecting body forces, (1) the weak form, using Galerkin's method and the Gauss divergence theorem, becomes (2) in which is the test function. The second term of the weak form equation is the residual contribution calculated by the stress divergence kernel.

The calculation of the Jacobian can be approximated with the elasticity tensor if the simulation solve type is JFNK:

(3) which is nonzero for .

If the solve type for the simulation is set to NEWTON the finite deformation Jacobian will need to be calculated. Set the parameter use_finite_deform_jacobian = true in this case.

note:Use of the Tensor Mechanics Master Action Recommended

The use_displaced_mesh parameter must be set correcting to ensure consistency in the equilibrium equation: if the stress is calculated with respect to the deformed mesh, the test function gradients must also be calculated with respect to the deformed mesh. The Tensor Mechanics MasterAction is designed to automatically determine and set the parameter correctly for the selected strain formulation. We recommend that users employ the Tensor Mechanics MasterAction whenever possible to ensure consistency between the test function gradients and the strain formulation selected.

In cylindrical coordinates, the divergence of a rank-2 tensor includes mixed term contributions. In the axisymmetric model we assume symmetric loading conditions, in addition to the zero out-of-plane shear strains, so that the residual computation is simplified.

(4)

The calculation of the Jacobian is similarly complex, requiring up to four terms in the calculation of the diagonal entries.

note:Notation Order Change

The axisymmetric system changes the order of the displacement vector from , usually seen in textbooks, to . Take care to follow this convention in your input files and when adding extra stresses.

Example Input File

note:Use RZ Coordinate Type

The coordinate type in the Problem block of the input file must be set to COORD_TYPE = RZ.

Using the tensor mechanics master action, as shown

[Modules/TensorMechanics/Master]
[./all]
strain = FINITE
block = 1
[../]
[]

(modules/tensor_mechanics/test/tests/2D_geometries/2D-RZ_finiteStrain_test.i)

the StressDivergenceRZTensors kernel will be automatically built when the coordinate system in the Problem block is specified for the axisymmetric RZ system,

[Problem]
coord_type = RZ
[]

(modules/tensor_mechanics/test/tests/2D_geometries/2D-RZ_finiteStrain_test.i)

and only two displacement variables are provided:

[GlobalParams]
displacements = 'disp_r disp_z'
[]

(modules/tensor_mechanics/test/tests/2D_geometries/2D-RZ_finiteStrain_test.i)

Input Parameters

• variableThe name of the variable that this Kernel operates on

C++ Type:NonlinearVariableName

Options:

Description:The name of the variable that this Kernel operates on

• componentAn integer corresponding to the direction the variable this kernel acts in. (0 refers to the radial and 1 to the axial displacement.)

C++ Type:unsigned int

Options:

Description:An integer corresponding to the direction the variable this kernel acts in. (0 refers to the radial and 1 to the axial displacement.)

• displacementsThe string of displacements suitable for the problem statement

C++ Type:std::vector

Options:

Description:The string of displacements suitable for the problem statement

Required Parameters

• temperatureThe name of the temperature variable used in the ComputeThermalExpansionEigenstrain. (Not required for simulations without temperature coupling.)

C++ Type:std::vector

Options:

Description:The name of the temperature variable used in the ComputeThermalExpansionEigenstrain. (Not required for simulations without temperature coupling.)

• base_nameMaterial property base name

C++ Type:std::string

Options:

Description:Material property base name

• use_finite_deform_jacobianFalseJacobian for corotational finite strain

Default:False

C++ Type:bool

Options:

Description:Jacobian for corotational finite strain

• out_of_plane_directionzThe direction of the out_of_plane_strain variable used in the WeakPlaneStress kernel.

Default:z

C++ Type:MooseEnum

Options:x y z

Description:The direction of the out_of_plane_strain variable used in the WeakPlaneStress kernel.

• volumetric_locking_correctionFalseSet to false to turn off volumetric locking correction

Default:False

C++ Type:bool

Options:

Description:Set to false to turn off volumetric locking correction

• thermal_eigenstrain_namethermal_eigenstrainThe eigenstrain_name used in the ComputeThermalExpansionEigenstrain.

Default:thermal_eigenstrain

C++ Type:std::string

Options:

Description:The eigenstrain_name used in the ComputeThermalExpansionEigenstrain.

• out_of_plane_strainThe name of the out_of_plane_strain variable used in the WeakPlaneStress kernel. Required only if want to provide off-diagonal Jacobian in plane stress analysis using weak formulation.

C++ Type:std::vector

Options:

Description:The name of the out_of_plane_strain variable used in the WeakPlaneStress kernel. Required only if want to provide off-diagonal Jacobian in plane stress analysis using weak formulation.

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

C++ Type:std::vector

Options:

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

Optional Parameters

• enableTrueSet the enabled status of the MooseObject.

Default:True

C++ Type:bool

Options:

Description:Set the enabled status of the MooseObject.

• save_inThe name of auxiliary variables to save this Kernel's residual contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

C++ Type:std::vector

Options:

Description:The name of auxiliary variables to save this Kernel's residual contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

• use_displaced_meshTrueWhether 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:True

C++ Type:bool

Options:

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.

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

C++ Type:std::vector

Options:

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

• seed0The seed for the master random number generator

Default:0

C++ Type:unsigned int

Options:

Description:The seed for the master random number generator

• diag_save_inThe name of auxiliary variables to save this Kernel's diagonal Jacobian contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

C++ Type:std::vector

Options:

Description:The name of auxiliary variables to save this Kernel's diagonal Jacobian contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

• implicitTrueDetermines whether this object is calculated using an implicit or explicit form

Default:True

C++ Type:bool

Options:

Description:Determines whether this object is calculated using an implicit or explicit form

• vector_tagsnontimeThe tag for the vectors this Kernel should fill

Default:nontime

C++ Type:MultiMooseEnum

Options:nontime time

Description:The tag for the vectors this Kernel should fill

• extra_vector_tagsThe extra tags for the vectors this Kernel should fill

C++ Type:std::vector

Options:

Description:The extra tags for the vectors this Kernel should fill

• matrix_tagssystemThe tag for the matrices this Kernel should fill

Default:system

C++ Type:MultiMooseEnum

Options:nontime system

Description:The tag for the matrices this Kernel should fill

• extra_matrix_tagsThe extra tags for the matrices this Kernel should fill

C++ Type:std::vector

Options:

Description:The extra tags for the matrices this Kernel should fill