Crack Front Definition

Used to describe geometric characteristics of the crack front for fracture integral calculations

Description

This object is used in the computation of fracture domain integrals. It is used to store information about the location of the crack front, and provides functions used by other objects involved in fracture integral calculation. It is not necessary to define this block in the input file, as it can be set up using the DomainIntegralAction.

Example Input File Syntax

[./crack_tip]
  type = CrackFrontDefinition
  crack_direction_method = CrackDirectionVector
  crack_front_points = '0.5 1.0 0'
  crack_direction_vector = '1 0 0'
  2d = true
  axis_2d = 2
[../]

Input Parameters

crack_direction_methodMethod to determine direction of crack propagation. Choices are: CrackDirectionVector CrackMouth CurvedCrackFront
C++ Type:MooseEnum
Options:CrackDirectionVector, CrackMouth, CurvedCrackFront
Controllable:No
Description:Method to determine direction of crack propagation. Choices are: CrackDirectionVector CrackMouth CurvedCrackFront

Required Parameters

2dFalseTreat body as two-dimensional
Default:False
C++ Type:bool
Controllable:No
Description:Treat body as two-dimensional
axis_2d2Out of plane axis for models treated as two-dimensional (0=x, 1=y, 2=z)
Default:2
C++ Type:unsigned int
Controllable:No
Description:Out of plane axis for models treated as two-dimensional (0=x, 1=y, 2=z)
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
closed_loopFalseSet of points forms forms a closed loop
Default:False
C++ Type:bool
Controllable:No
Description:Set of points forms forms a closed loop
crack_direction_vectorDirection of crack propagation
C++ Type:libMesh::VectorValue<double>
Controllable:No
Description:Direction of crack propagation
crack_direction_vector_end_1Direction of crack propagation for the node at end 1 of the crack
C++ Type:libMesh::VectorValue<double>
Controllable:No
Description:Direction of crack propagation for the node at end 1 of the crack
crack_direction_vector_end_2Direction of crack propagation for the node at end 2 of the crack
C++ Type:libMesh::VectorValue<double>
Controllable:No
Description:Direction of crack propagation for the node at end 2 of the crack
crack_end_direction_methodNoSpecialTreatmentMethod to determine direction of crack propagation at ends of crack. Choices are: NoSpecialTreatment CrackDirectionVector CrackTangentVector
Default:NoSpecialTreatment
C++ Type:MooseEnum
Options:NoSpecialTreatment, CrackDirectionVector, CrackTangentVector
Controllable:No
Description:Method to determine direction of crack propagation at ends of crack. Choices are: NoSpecialTreatment CrackDirectionVector CrackTangentVector
crack_front_pointsSet of points to define crack front
C++ Type:std::vector<libMesh::Point>
Controllable:No
Description:Set of points to define crack front
crack_front_points_providerThe UserObject provides the crack front points from XFEM GeometricCutObject
C++ Type:UserObjectName
Controllable:No
Description:The UserObject provides the crack front points from XFEM GeometricCutObject
crack_mouth_boundaryBoundaries whose average coordinate defines the crack mouth
C++ Type:std::vector<BoundaryName>
Controllable:No
Description:Boundaries whose average coordinate defines the crack mouth
crack_tangent_vector_end_1Direction of crack tangent for the node at end 1 of the crack
C++ Type:libMesh::VectorValue<double>
Controllable:No
Description:Direction of crack tangent for the node at end 1 of the crack
crack_tangent_vector_end_2Direction of crack tangent for the node at end 2 of the crack
C++ Type:libMesh::VectorValue<double>
Controllable:No
Description:Direction of crack tangent for the node at end 2 of the crack
disp_xVariable containing the x displacement
C++ Type:VariableName
Controllable:No
Description:Variable containing the x displacement
disp_yVariable containing the y displacement
C++ Type:VariableName
Controllable:No
Description:Variable containing the y displacement
disp_zVariable containing the z displacement
C++ Type:VariableName
Controllable:No
Description:Variable containing the z displacement
execute_onTIMESTEP_ENDThe list of flag(s) indicating when this object should be executed, the available options include NONE, INITIAL, LINEAR, NONLINEAR, TIMESTEP_END, TIMESTEP_BEGIN, MULTIAPP_FIXED_POINT_END, MULTIAPP_FIXED_POINT_BEGIN, FINAL, CUSTOM, ALWAYS.
Default:TIMESTEP_END
C++ Type:ExecFlagEnum
Options:NONE, INITIAL, LINEAR, NONLINEAR, TIMESTEP_END, TIMESTEP_BEGIN, MULTIAPP_FIXED_POINT_END, MULTIAPP_FIXED_POINT_BEGIN, FINAL, CUSTOM, ALWAYS
Controllable:No
Description:The list of flag(s) indicating when this object should be executed, the available options include NONE, INITIAL, LINEAR, NONLINEAR, TIMESTEP_END, TIMESTEP_BEGIN, MULTIAPP_FIXED_POINT_END, MULTIAPP_FIXED_POINT_BEGIN, FINAL, CUSTOM, ALWAYS.
first_ringThe number of rings of nodes to generate
C++ Type:unsigned int
Controllable:No
Description:The number of rings of nodes to generate
intersecting_boundaryBoundaries intersected by ends of crack
C++ Type:std::vector<BoundaryName>
Controllable:No
Description:Boundaries intersected by ends of crack
j_integral_radius_innerRadius for J-Integral calculation
C++ Type:std::vector<double>
Controllable:No
Description:Radius for J-Integral calculation
j_integral_radius_outerRadius for J-Integral calculation
C++ Type:std::vector<double>
Controllable:No
Description:Radius for J-Integral calculation
last_ringThe number of rings of nodes to generate
C++ Type:unsigned int
Controllable:No
Description:The number of rings of nodes to generate
nringsThe number of rings of nodes to generate
C++ Type:unsigned int
Controllable:No
Description:The number of rings of nodes to generate
number_points_from_providerThe number of crack front points, only needed if crack_front_points_provider is used.
C++ Type:unsigned int
Controllable:No
Description:The number of crack front points, only needed if crack_front_points_provider is used.
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.
q_function_ringsFalseGenerate rings of nodes for q-function
Default:False
C++ Type:bool
Controllable:No
Description:Generate rings of nodes for q-function
q_function_typeGeometryThe method used to define the integration domain. Options are: Geometry Topology
Default:Geometry
C++ Type:MooseEnum
Options:Geometry, Topology
Controllable:No
Description:The method used to define the integration domain. Options are: Geometry Topology
symmetry_planeAccount for a symmetry plane passing through the plane of the crack, normal to the specified axis (0=x, 1=y, 2=z)
C++ Type:unsigned int
Controllable:No
Description:Account for a symmetry plane passing through the plane of the crack, normal to the specified axis (0=x, 1=y, 2=z)
t_stressFalseCalculate T-stress
Default:False
C++ Type:bool
Controllable:No
Description:Calculate T-stress

Optional Parameters

allow_duplicate_execution_on_initialFalseIn the case where this UserObject is depended upon by an initial condition, allow it to be executed twice during the initial setup (once before the IC and again after mesh adaptivity (if applicable).
Default:False
C++ Type:bool
Controllable:No
Description:In the case where this UserObject is depended upon by an initial condition, allow it to be executed twice during the initial setup (once before the IC and again after mesh adaptivity (if applicable).
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.
execution_order_group0Execution order groups are executed in increasing order (e.g., the lowest number is executed first). Note that negative group numbers may be used to execute groups before the default (0) group. Please refer to the user object documentation for ordering of user object execution within a group.
Default:0
C++ Type:int
Controllable:No
Description:Execution order groups are executed in increasing order (e.g., the lowest number is executed first). Note that negative group numbers may be used to execute groups before the default (0) group. Please refer to the user object documentation for ordering of user object execution within a group.
force_postauxFalseForces the UserObject to be executed in POSTAUX
Default:False
C++ Type:bool
Controllable:No
Description:Forces the UserObject to be executed in POSTAUX
force_preauxFalseForces the UserObject to be executed in PREAUX
Default:False
C++ Type:bool
Controllable:No
Description:Forces the UserObject to be executed in PREAUX
force_preicFalseForces the UserObject to be executed in PREIC during initial setup
Default:False
C++ Type:bool
Controllable:No
Description:Forces the UserObject to be executed in PREIC during initial setup
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

(../moose/modules/xfem/test/tests/crack_tip_enrichment/edge_crack_2d.i)

[XFEM]
  qrule = volfrac
  output_cut_plane = true
  use_crack_tip_enrichment = true
  crack_front_definition = crack_tip
  enrichment_displacements = 'enrich1_x enrich2_x enrich3_x enrich4_x enrich1_y enrich2_y enrich3_y enrich4_y'
  displacements = 'disp_x disp_y'
  cut_off_boundary = all
  cut_off_radius = 0.2
[]

[UserObjects]
  [./line_seg_cut_uo]
    type = LineSegmentCutUserObject
    cut_data = '0.0 1.0 0.5 1.0'
    time_start_cut = 0.0
    time_end_cut = 0.0
  [../]
  [./crack_tip]
    type = CrackFrontDefinition
    crack_direction_method = CrackDirectionVector
    crack_front_points = '0.5 1.0 0'
    crack_direction_vector = '1 0 0'
    2d = true
    axis_2d = 2
  [../]
[]

[Mesh]
  [gen]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 5
    ny = 9
    xmin = 0.0
    xmax = 1.0
    ymin = 0.0
    ymax = 2.0
    elem_type = QUAD4
  []
  [./all_node]
    type = BoundingBoxNodeSetGenerator
    new_boundary = 'all'
    top_right = '1 2 0'
    bottom_left = '0 0 0'
    input = gen
  [../]
  [./right_bottom_node]
    type = ExtraNodesetGenerator
    new_boundary = 'right_bottom_node'
    coord = '1.0 0.0'
    input = all_node
  [../]
  [./right_top_node]
    type = ExtraNodesetGenerator
    new_boundary = 'right_top_node'
    coord = '1.0 2.0'
    input = right_bottom_node
  [../]
[]

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

[AuxVariables]
 [./saved_x]
  [../]
  [./saved_y]
  [../]
  [./stress_xx]
    order = CONSTANT
    family = MONOMIAL
  [../]
  [./stress_yy]
    order = CONSTANT
    family = MONOMIAL
  [../]
  [./stress_xy]
    order = CONSTANT
    family = MONOMIAL
  [../]
  [./vonmises]
    order = CONSTANT
    family = MONOMIAL
  [../]
[]

[Kernels]
  [./TensorMechanics]
    displacements = 'disp_x disp_y'
  [../]
[]

[AuxKernels]
  [./stress_xx]
    type = RankTwoAux
    rank_two_tensor = stress
    variable = stress_xx
    index_i = 0
    index_j = 0
    execute_on = timestep_end
  [../]
  [./stress_yy]
    type = RankTwoAux
    rank_two_tensor = stress
    variable = stress_yy
    index_i = 1
    index_j = 1
    execute_on = timestep_end
  [../]
  [./stress_xy]
    type = RankTwoAux
    rank_two_tensor = stress
    variable = stress_xy
    index_i = 0
    index_j = 1
    execute_on = timestep_end
  [../]
  [./vonmises]
    type = RankTwoScalarAux
    rank_two_tensor = stress
    variable = vonmises
    scalar_type = vonmisesStress
    execute_on = timestep_end
  [../]
[]

[BCs]
  [./top_y]
    type = Pressure
    variable = disp_y
    boundary = top
    factor = -1
    displacements = 'disp_x disp_y'
  [../]
  [./bottom_y]
    type = Pressure
    variable = disp_y
    boundary = bottom
    factor = -1
    displacements = 'disp_x disp_y'
  [../]
  [./fix_y]
    type = DirichletBC
    boundary = right_bottom_node
    variable = disp_y
    value = 0.0
  [../]
  [./fix_x]
    type = DirichletBC
    boundary = right_bottom_node
    variable = disp_x
    value =  0.0
  [../]
  [./fix_x2]
    type = DirichletBC
    boundary = right_top_node
    variable = disp_x
    value =  0.0
  [../]
[]

[Materials]
  [./elasticity_tensor]
    type = ComputeIsotropicElasticityTensor
    youngs_modulus = 1e6
    poissons_ratio = 0.3
  [../]
  [./strain]
    type = ComputeCrackTipEnrichmentSmallStrain
    displacements = 'disp_x disp_y'
    crack_front_definition = crack_tip
    enrichment_displacements = 'enrich1_x enrich2_x enrich3_x enrich4_x enrich1_y enrich2_y enrich3_y enrich4_y'
  [../]
  [./stress]
    type = ComputeLinearElasticStress
  [../]
[]

[Executioner]
  type = Transient

  solve_type = 'PJFNK'

  petsc_options_iname = '-pc_type -pc_factor_mat_solver_package'
  petsc_options_value = 'lu     superlu_dist'

  line_search = 'none'

  # Since we do not sub-triangularize the tip element,
  # we need to use higher order quadrature rule to improve
  # integration accuracy.
  # Here second = SECOND is for regression test only.
  # However, order = SIXTH is recommended.
  [./Quadrature]
    type = GAUSS
    order = SECOND
  [../]

  [./Predictor]
    type = SimplePredictor
    scale = 1.0
  [../]

  # controls for linear iterations
  l_max_its = 10
  l_tol = 1e-4

  # controls for nonlinear iterations
  nl_max_its = 100
  nl_rel_tol = 1e-12 #11
  nl_abs_tol = 1e-12 #12

  # time control
  start_time = 0.0
  dt = 1.0
  end_time = 1.0
  dtmin = 1.0
[]

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


[Outputs]
  file_base = edge_crack_2d_out
  exodus = true
  [./console]
    type = Console
    output_linear = true
  [../]
[]