Linear Viscoelastic Stress Update

Calculates an admissible state (stress that lies on or within the yield surface, plastic strains, internal parameters, etc). This class is intended to be a parent class for classes with specific constitutive models.

Description

This computes the inelastic strain increment resulting from a linear viscoelastic material such as a GeneralizedKelvinVoigtModel or a GeneralizedMaxwellModel material. It uses an incremental strain approximation (either incremental small strains, or finite strains), and needs to be used in conjunction with ComputeMultipleInelasticStress or a similar stress calculator.

Example Input File Syntax

[./creep]
  type = LinearViscoelasticStressUpdate
[../]

LinearViscoelasticStressUpdate must be run in conjunction with the inelastic strain return mapping stress calculator as shown below:

[./stress]
  type = ComputeMultipleInelasticStress
  inelastic_models = 'creep'
[../]

Input Parameters

apparent_creep_strainapparent_creep_strainname of the apparent creep strain (defined by a LinearViscoelasticityBase material)
Default:apparent_creep_strain
C++ Type:std::string
Controllable:No
Description:name of the apparent creep strain (defined by a LinearViscoelasticityBase material)
apparent_elasticity_tensorapparent_elasticity_tensorname of the apparent elasticity tensor (defined by a LinearViscoelasticityBase material)
Default:apparent_elasticity_tensor
C++ Type:std::string
Controllable:No
Description:name of the apparent elasticity tensor (defined by a LinearViscoelasticityBase material)
base_nameOptional parameter that defines a prefix for all material properties related to this stress update model. This allows for multiple models of the same type to be used without naming conflicts.
C++ Type:std::string
Controllable:No
Description:Optional parameter that defines a prefix for all material properties related to this stress update model. This allows for multiple models of the same type to be used without naming conflicts.
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
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.
elasticity_tensor_invelasticity_tensor_invname of the real compliance tensor (defined by a LinearViscoelasticityBase material)
Default:elasticity_tensor_inv
C++ Type:std::string
Controllable:No
Description:name of the real compliance tensor (defined by a LinearViscoelasticityBase material)
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

(../moose/modules/tensor_mechanics/test/tests/visco/gen_maxwell_driving.i)

# Represents a unique Maxwell module with E = 10GPa and eta = 10 days with an imposed eigenstrain alpha = 0.001.
# The behavior is set up so that the creep strain is driven by both the elastic stress and the internal
# stress induced by the eigenstrain (E * alpha).
#
# In this test, the specimen is free of external stress (sigma = 0) so the creep deformation only derives from
# the eigenstrain. The total strain to be expected is:
#     epsilon = alpha * (1 + t / eta)
# Both the stress and the elastic strain are 0.
#
[Mesh]
  type = GeneratedMesh
  dim = 3
  nx = 1
  ny = 1
  nz = 1
  elem_type = HEX8
  displacements = 'disp_x disp_y disp_z'
[]

[Variables]
  [./disp_x]
    order = FIRST
    family = LAGRANGE
  [../]
  [./disp_y]
    order = FIRST
    family = LAGRANGE
  [../]
  [./disp_z]
    order = FIRST
    family = LAGRANGE
  [../]
[]

[AuxVariables]
  [./stress_xx]
    order = CONSTANT
    family = MONOMIAL
  [../]
  [./strain_xx]
    order = CONSTANT
    family = MONOMIAL
  [../]
  [./creep_strain_xx]
    order = CONSTANT
    family = MONOMIAL
  [../]
[]

[Kernels]
  [./TensorMechanics]
    displacements = 'disp_x disp_y disp_z'
    use_displaced_mesh = true
  [../]
[]

[AuxKernels]
  [./stress_xx]
    type = RankTwoAux
    variable = stress_xx
    rank_two_tensor = stress
    index_j = 0
    index_i = 0
    execute_on = timestep_end
  [../]
  [./strain_xx]
    type = RankTwoAux
    variable = strain_xx
    rank_two_tensor = total_strain
    index_j = 0
    index_i = 0
    execute_on = timestep_end
  [../]
  [./creep_strain_xx]
    type = RankTwoAux
    variable = creep_strain_xx
    rank_two_tensor = creep_strain
    index_j = 0
    index_i = 0
    execute_on = timestep_end
  [../]
[]

[BCs]
  [./symmy]
    type = DirichletBC
    variable = disp_y
    boundary = bottom
    value = 0
  [../]
  [./symmx]
    type = DirichletBC
    variable = disp_x
    boundary = left
    value = 0
  [../]
  [./symmz]
    type = DirichletBC
    variable = disp_z
    boundary = back
    value = 0
  [../]
[]

[Materials]
  [./eigen]
    type = ComputeEigenstrain
    eigenstrain_name = eigen_true
    eigen_base = '1e-3 1e-3 1e-3 0 0 0'
  [../]
  [./maxwell]
    type = GeneralizedMaxwellModel
    creep_modulus = '10e9'
    creep_viscosity = '10'
    poisson_ratio = 0.2
    young_modulus = 10e9
    driving_eigenstrain = eigen_true
  [../]
  [./stress]
    type = ComputeMultipleInelasticStress
    inelastic_models = 'creep'
  [../]
  [./creep]
    type = LinearViscoelasticStressUpdate
  [../]
  [./strain]
    type = ComputeIncrementalSmallStrain
    displacements = 'disp_x disp_y disp_z'
    eigenstrain_names = 'eigen_true'
  [../]
[]

[UserObjects]
  [./update]
    type = LinearViscoelasticityManager
    viscoelastic_model = maxwell
  [../]
[]

[Postprocessors]
  [./stress_xx]
    type = ElementAverageValue
    variable = stress_xx
    block = 'ANY_BLOCK_ID 0'
  [../]
  [./strain_xx]
    type = ElementAverageValue
    variable = strain_xx
    block = 'ANY_BLOCK_ID 0'
  [../]
  [./creep_strain_xx]
    type = ElementAverageValue
    variable = creep_strain_xx
    block = 'ANY_BLOCK_ID 0'
  [../]
[]

[Preconditioning]
  [./smp]
    type = SMP
    full = true
  [../]
[]

[Executioner]
  type = Transient

  l_max_its  = 50
  l_tol      = 1e-8
  nl_max_its = 20
  nl_rel_tol = 1e-11
  nl_abs_tol = 1e-8

  dtmin = 0.01
  end_time = 100
  [./TimeStepper]
    type = LogConstantDT
    first_dt = 0.1
    log_dt = 0.1
  [../]

[]

[Outputs]
  file_base = gen_maxwell_driving_out
  exodus = true
[]

(../moose/modules/tensor_mechanics/test/tests/visco/gen_maxwell_driving.i)

# Represents a unique Maxwell module with E = 10GPa and eta = 10 days with an imposed eigenstrain alpha = 0.001.
# The behavior is set up so that the creep strain is driven by both the elastic stress and the internal
# stress induced by the eigenstrain (E * alpha).
#
# In this test, the specimen is free of external stress (sigma = 0) so the creep deformation only derives from
# the eigenstrain. The total strain to be expected is:
#     epsilon = alpha * (1 + t / eta)
# Both the stress and the elastic strain are 0.
#
[Mesh]
  type = GeneratedMesh
  dim = 3
  nx = 1
  ny = 1
  nz = 1
  elem_type = HEX8
  displacements = 'disp_x disp_y disp_z'
[]

[Variables]
  [./disp_x]
    order = FIRST
    family = LAGRANGE
  [../]
  [./disp_y]
    order = FIRST
    family = LAGRANGE
  [../]
  [./disp_z]
    order = FIRST
    family = LAGRANGE
  [../]
[]

[AuxVariables]
  [./stress_xx]
    order = CONSTANT
    family = MONOMIAL
  [../]
  [./strain_xx]
    order = CONSTANT
    family = MONOMIAL
  [../]
  [./creep_strain_xx]
    order = CONSTANT
    family = MONOMIAL
  [../]
[]

[Kernels]
  [./TensorMechanics]
    displacements = 'disp_x disp_y disp_z'
    use_displaced_mesh = true
  [../]
[]

[AuxKernels]
  [./stress_xx]
    type = RankTwoAux
    variable = stress_xx
    rank_two_tensor = stress
    index_j = 0
    index_i = 0
    execute_on = timestep_end
  [../]
  [./strain_xx]
    type = RankTwoAux
    variable = strain_xx
    rank_two_tensor = total_strain
    index_j = 0
    index_i = 0
    execute_on = timestep_end
  [../]
  [./creep_strain_xx]
    type = RankTwoAux
    variable = creep_strain_xx
    rank_two_tensor = creep_strain
    index_j = 0
    index_i = 0
    execute_on = timestep_end
  [../]
[]

[BCs]
  [./symmy]
    type = DirichletBC
    variable = disp_y
    boundary = bottom
    value = 0
  [../]
  [./symmx]
    type = DirichletBC
    variable = disp_x
    boundary = left
    value = 0
  [../]
  [./symmz]
    type = DirichletBC
    variable = disp_z
    boundary = back
    value = 0
  [../]
[]

[Materials]
  [./eigen]
    type = ComputeEigenstrain
    eigenstrain_name = eigen_true
    eigen_base = '1e-3 1e-3 1e-3 0 0 0'
  [../]
  [./maxwell]
    type = GeneralizedMaxwellModel
    creep_modulus = '10e9'
    creep_viscosity = '10'
    poisson_ratio = 0.2
    young_modulus = 10e9
    driving_eigenstrain = eigen_true
  [../]
  [./stress]
    type = ComputeMultipleInelasticStress
    inelastic_models = 'creep'
  [../]
  [./creep]
    type = LinearViscoelasticStressUpdate
  [../]
  [./strain]
    type = ComputeIncrementalSmallStrain
    displacements = 'disp_x disp_y disp_z'
    eigenstrain_names = 'eigen_true'
  [../]
[]

[UserObjects]
  [./update]
    type = LinearViscoelasticityManager
    viscoelastic_model = maxwell
  [../]
[]

[Postprocessors]
  [./stress_xx]
    type = ElementAverageValue
    variable = stress_xx
    block = 'ANY_BLOCK_ID 0'
  [../]
  [./strain_xx]
    type = ElementAverageValue
    variable = strain_xx
    block = 'ANY_BLOCK_ID 0'
  [../]
  [./creep_strain_xx]
    type = ElementAverageValue
    variable = creep_strain_xx
    block = 'ANY_BLOCK_ID 0'
  [../]
[]

[Preconditioning]
  [./smp]
    type = SMP
    full = true
  [../]
[]

[Executioner]
  type = Transient

  l_max_its  = 50
  l_tol      = 1e-8
  nl_max_its = 20
  nl_rel_tol = 1e-11
  nl_abs_tol = 1e-8

  dtmin = 0.01
  end_time = 100
  [./TimeStepper]
    type = LogConstantDT
    first_dt = 0.1
    log_dt = 0.1
  [../]

[]

[Outputs]
  file_base = gen_maxwell_driving_out
  exodus = true
[]