ComputeMeanThermalExpansionFunctionEigenstrain

Computes eigenstrain due to thermal expansion using a function that describes the mean thermal expansion as a function of temperature

Description

This model computes the eigenstrain tensor resulting from isotropic thermal expansion where the temperature-dependent thermal expansion is defined by a user-supplied function that describes the mean thermal expansion coefficient as a function of temperature, . This function is defined relative to a reference temperature, , such that the total expansion at a given temperature relative to the refererence temperature is . Following the notation of Niffenegger and Reichlin (2012), is defined as:

where is the length of a body at the current temperature, and is the length of that body at the reference temperature.

It is important to emphasize that this reference temperature is tied to the definition of the thermal expansion function, and differs in general from the stress-free temperature for a specific simulation. For the general case where the stress-free temperature, , differs from the reference temperature, the total thermal expansion eigenstrain is computed as:

where is the current temperature and is the identity matrix. Note that the denominator in this equation is a correction to account for the ratio of to . As discussed in Niffenegger and Reichlin (2012), that ratio is very close to 1, so it is not strictly necessary to include that correction, but it is done here for completeness.

Example Input File Syntax

[./thermal_expansion_strain1]
  type = ComputeMeanThermalExpansionFunctionEigenstrain
  block = 1
  thermal_expansion_function = cte_func_mean
  thermal_expansion_function_reference_temperature = 0.5
  stress_free_temperature = 0.0
  temperature = temp
  eigenstrain_name = eigenstrain
[../]
(../moose/modules/tensor_mechanics/test/tests/thermal_expansion_function/finite_const.i)

The eigenstrain_name parameter value must also be set for the strain calculator, and an example parameter setting is shown below:

[Modules/TensorMechanics/Master]
  [Modules/TensorMechanics/Master]
    [Modules/TensorMechanics/Master]
      [./all]
        strain = FINITE
        add_variables = true
        eigenstrain_names = eigenstrain
        generate_output = 'strain_xx strain_yy strain_zz'
      [../]
    []
  []
[]
(../moose/modules/tensor_mechanics/test/tests/thermal_expansion_function/finite_const.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.

  • stress_free_temperatureReference temperature at which there is no thermal expansion for thermal eigenstrain calculation

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

    Controllable:No

    Description:Reference temperature at which there is no thermal expansion for thermal eigenstrain calculation

  • thermal_expansion_functionFunction describing the mean thermal expansion as a function of temperature

    C++ Type:FunctionName

    Controllable:No

    Description:Function describing the mean thermal expansion as a function of temperature

  • thermal_expansion_function_reference_temperatureReference temperature for thermal_exansion_function (IMPORTANT: this is different in general from the stress_free_temperature)

    C++ Type:double

    Controllable:No

    Description:Reference temperature for thermal_exansion_function (IMPORTANT: this is different in general from the stress_free_temperature)

Required Parameters

  • base_nameOptional parameter that allows the user to define multiple mechanics material systems on the same block, i.e. for multiple phases

    C++ Type:std::string

    Controllable:No

    Description:Optional parameter that allows the user to define multiple mechanics material systems on the same block, i.e. for multiple phases

  • 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.

  • mean_thermal_expansion_coefficient_nameName of the mean coefficient of thermal expansion.

    C++ Type:MaterialPropertyName

    Controllable:No

    Description:Name of the mean coefficient of thermal expansion.

  • 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.

  • temperatureCoupled temperature

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

    Controllable:No

    Description:Coupled temperature

  • use_old_temperatureFalseFlag to optionally use the temperature value from the previous timestep.

    Default:False

    C++ Type:bool

    Controllable:No

    Description:Flag to optionally use the temperature value from the previous timestep.

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

  • thermal_expansion_scale_factor1Scaling factor on the thermal expansion strain. This input parameter can be used to perform sensitivity analysis on thermal expansion.

    Default:1

    C++ Type:double

    Controllable:No

    Description:Scaling factor on the thermal expansion strain. This input parameter can be used to perform sensitivity analysis on thermal expansion.

  • 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

References

  1. Markus Niffenegger and Klaus Reichlin. The proper use of thermal expansion coefficients in finite element calculations. Nuclear Engineering and Design, 243:356–359, February 2012. doi:10.1016/j.nucengdes.2011.12.006.[BibTeX]