Compute Mean Thermal Expansion Function Eigenstrain

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:

(1) 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:

(2) 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
[../]
(modules/tensor_mechanics/test/tests/thermal_expansion_function/thermal_expansion_function_finite_const_alpha_test.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]
  [./all]
    strain = FINITE
    incremental = true
    add_variables = true
    eigenstrain_names = eigenstrain
    generate_output = 'strain_xx strain_yy strain_zz'
  [../]
[]
(modules/tensor_mechanics/test/tests/thermal_expansion_function/thermal_expansion_function_finite_const_alpha_test.i)

Input Parameters

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

    C++ Type:std::vector

    Options:

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

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

    C++ Type:double

    Options:

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

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

    C++ Type:FunctionName

    Options:

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

  • 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

    Options:

    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.

Required Parameters

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

    Default:True

    C++ Type:bool

    Options:

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

  • temperatureCoupled temperature

    C++ Type:std::vector

    Options:

    Description:Coupled temperature

  • 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

    Options:

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

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

    C++ Type:std::vector

    Options:

    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

    Options:

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

Optional Parameters

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

    C++ Type:std::vector

    Options:

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

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

    Default:none

    C++ Type:std::vector

    Options:

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

Outputs Parameters

  • enableTrueSet the enabled status of the MooseObject.

    Default:True

    C++ Type:bool

    Options:

    Description:Set the enabled status of the MooseObject.

  • 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

    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

  • 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

  • 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 computeSubdomainProperties() 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

    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 computeSubdomainProperties() for the 0th quadrature point, and then copy that value to the other qps. Evaluations on element qps will be skipped

Advanced Parameters

Input Files

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]