ComputeEigenstrainFromInitialStress

Computes an eigenstrain from an initial stress

Description

Computes an eigenstrain, , defined by , where is the elasticity tensor and is the initial stress entered by the user. The initial stress is entered as a vector of 9 Functions, which may be optionally multiplied by a vector of 9 AuxVariables.

This allows a user to enter an insitu stress in rock-mechanics problems, for instance, by specifying the component to be a function of depth into the ground, and the , , and components of the initial stress to be related to the maximum and minimum principal horizontal tectonic stresses. A general anisotropic initial stress is allowed. Using AuxVariables to set the initial stress may be advantageous when reading from a solution file using a SolutionAux.

The eigenstrain thus computed is added to the mechanical strain on the first time step, and is unchanged in subsequent timesteps. The eigenstrain thus computed is given a name that is specified by the user, and that name must be included in the eigenstrain_names input parameter of the strain calculator (eg, in ComputeSmallStrain), otherwise MOOSE will not add the eigenstrain to the mechanical strain!

warningwarning:Time-dependent elasticity tensors

The eigenstrain is computed on the first time step, using the elasticity tensor; hence, the elasticity tensor should not be time-varying in the first timestep.

Example Input File Syntax

[Materials]
  [./elasticity_tensor]
    type = ComputeIsotropicElasticityTensor
    youngs_modulus = 1
    poissons_ratio = 0.25
  [../]
  [./strain]
    type = ComputeSmallStrain
    eigenstrain_names = ini_stress
  [../]
  [./strain_from_initial_stress]
    type = ComputeEigenstrainFromInitialStress
    initial_stress = 'kxx 0 0  0 kxx 0  0 0 weight'
    eigenstrain_name = ini_stress
  [../]
  [./stress]
    type = ComputeLinearElasticStress
  [../]
[]
(moose/modules/tensor_mechanics/test/tests/initial_stress/gravity.i)

In this example the eigenstrain is given the name ini_stress. This name is passed to the ComputeSmallStrain strain calculator using the eigenstrain_names parameter. The initial stress is defined by the functions defined in

[Functions]
  [./weight]
    type = ParsedFunction
    expression = '0.5*z' # initial stress that should result from the weight force
  [../]
  [./kxx]
    type = ParsedFunction
    expression = '0.4*z' # some arbitrary xx and yy stress that should not affect the result
  [../]
[]
(moose/modules/tensor_mechanics/test/tests/initial_stress/gravity.i)

Input Parameters

  • eigenstrain_nameMaterial property name for the eigenstrain tensor computed by this model. IMPORTANT: The name of this property must also be provided to the strain calculator.

    C++ Type:std::string

    Controllable:No

    Description:Material property name for the eigenstrain tensor computed by this model. IMPORTANT: The name of this property must also be provided to the strain calculator.

  • initial_stressA list of functions describing the initial stress. There must be 9 of these, corresponding to the xx, yx, zx, xy, yy, zy, xz, yz, zz components respectively. To compute the eigenstrain correctly, your elasticity tensor should not be time-varying in the first timestep

    C++ Type:std::vector<FunctionName>

    Controllable:No

    Description:A list of functions describing the initial stress. There must be 9 of these, corresponding to the xx, yx, zx, xy, yy, zy, xz, yz, zz components respectively. To compute the eigenstrain correctly, your elasticity tensor should not be time-varying in the first timestep

Required Parameters

  • base_nameThe base_name for the elasticity tensor that will be used to compute strain from stress. Do not provide any base_name if your elasticity tensor does not use one.

    C++ Type:std::string

    Controllable:No

    Description:The base_name for the elasticity tensor that will be used to compute strain from stress. Do not provide any base_name if your elasticity tensor does not use one.

  • blockThe list of blocks (ids or names) that this object will be applied

    C++ Type:std::vector<SubdomainName>

    Controllable:No

    Description:The list of blocks (ids or names) that this object will be applied

  • boundaryThe list of boundaries (ids or names) from the mesh where this object applies

    C++ Type:std::vector<BoundaryName>

    Controllable:No

    Description:The list of boundaries (ids or names) from the mesh where this object applies

  • computeTrueWhen false, MOOSE will not call compute methods on this material. The user must call computeProperties() after retrieving the MaterialBase via MaterialBasePropertyInterface::getMaterialBase(). Non-computed MaterialBases are not sorted for dependencies.

    Default:True

    C++ Type:bool

    Controllable:No

    Description:When false, MOOSE will not call compute methods on this material. The user must call computeProperties() after retrieving the MaterialBase via MaterialBasePropertyInterface::getMaterialBase(). Non-computed MaterialBases are not sorted for dependencies.

  • constant_onNONEWhen ELEMENT, MOOSE will only call computeQpProperties() for the 0th quadrature point, and then copy that value to the other qps.When SUBDOMAIN, MOOSE will only call computeQpProperties() for the 0th quadrature point, and then copy that value to the other qps. Evaluations on element qps will be skipped

    Default:NONE

    C++ Type:MooseEnum

    Options:NONE, ELEMENT, SUBDOMAIN

    Controllable:No

    Description:When ELEMENT, MOOSE will only call computeQpProperties() for the 0th quadrature point, and then copy that value to the other qps.When SUBDOMAIN, MOOSE will only call computeQpProperties() for the 0th quadrature point, and then copy that value to the other qps. Evaluations on element qps will be skipped

  • declare_suffixAn optional suffix parameter that can be appended to any declared properties. The suffix will be prepended with a '_' character.

    C++ Type:MaterialPropertyName

    Controllable:No

    Description:An optional suffix parameter that can be appended to any declared properties. The suffix will be prepended with a '_' character.

  • initial_stress_auxA list of 9 AuxVariables describing the initial stress. If provided, each of these is multiplied by its corresponding initial_stress function to obtain the relevant component of initial stress.

    C++ Type:std::vector<VariableName>

    Controllable:No

    Description:A list of 9 AuxVariables describing the initial stress. If provided, each of these is multiplied by its corresponding initial_stress function to obtain the relevant component of initial stress.

  • prop_getter_suffixAn optional suffix parameter that can be appended to any attempt to retrieve/get material properties. The suffix will be prepended with a '_' character.

    C++ Type:MaterialPropertyName

    Controllable:No

    Description:An optional suffix parameter that can be appended to any attempt to retrieve/get material properties. The suffix will be prepended with a '_' character.

Optional Parameters

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

    C++ Type:std::vector<std::string>

    Controllable:No

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

  • enableTrueSet the enabled status of the MooseObject.

    Default:True

    C++ Type:bool

    Controllable:Yes

    Description:Set the enabled status of the MooseObject.

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

    Default:True

    C++ Type:bool

    Controllable:No

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

  • seed0The seed for the master random number generator

    Default:0

    C++ Type:unsigned int

    Controllable:No

    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

    Controllable:No

    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.

Advanced Parameters

  • output_propertiesList of material properties, from this material, to output (outputs must also be defined to an output type)

    C++ Type:std::vector<std::string>

    Controllable:No

    Description:List of material properties, from this material, to output (outputs must also be defined to an output type)

  • outputsnone Vector of output names where you would like to restrict the output of variables(s) associated with this object

    Default:none

    C++ Type:std::vector<OutputName>

    Controllable:No

    Description:Vector of output names where you would like to restrict the output of variables(s) associated with this object

Outputs Parameters