- cracking_stressThe stress threshold beyond which cracking occurs. Negative values prevent cracking.
C++ Type:std::vector<VariableName>
Controllable:No
Description:The stress threshold beyond which cracking occurs. Negative values prevent cracking.
- inelastic_modelsThe material objects to use to calculate stress and inelastic strains. Note: specify creep models first and plasticity models second.
C++ Type:std::vector<MaterialName>
Controllable:No
Description:The material objects to use to calculate stress and inelastic strains. Note: specify creep models first and plasticity models second.
- softening_modelsThe material objects used to compute softening behavior for loading a crack.Either 1 or 3 models must be specified. If a single model is specified, it isused for all directions. If 3 models are specified, they will be used for the3 crack directions in sequence
C++ Type:std::vector<MaterialName>
Controllable:No
Description:The material objects used to compute softening behavior for loading a crack.Either 1 or 3 models must be specified. If a single model is specified, it isused for all directions. If 3 models are specified, they will be used for the3 crack directions in sequence
Compute Smeared Cracking Stress
Compute stress using a fixed smeared cracking model
Description
This class implements a fixed smeared cracking model, which represents cracking as a softening stress-strain law at the material points as opposed to introducing topographic changes to the mesh, as would be the case with a discrete cracking model.
In this model, principal stresses are compared to a critical stress. If one of the principal stresses exceeds the critical stress, the material point is considered cracked in that direction, and the model transitions to an orthotropic model, in which the stress in the cracked direction is decreased according to a softening law. Material behavior in the cracking direction is affected in two ways: reduction of the stiffness in that direction, and adjusting the stress to follow the softening curve.
Interaction with Inelastic Models
This class derives from ComputeMultipleInelasticStrain, and prior to cracking, allows multiple inelastic models to be active. Once cracking occurs, the inelastic strains at that material point are preserved, but those models are no longer called for the duration of the simulation, and inelastic strains from those other models are no longer permitted to evolve.
Cracking Direction Determination
The orientation of the principal coordinate system is determined from the eigenvectors of the elastic strain tensor. However, once a crack direction is determined, that direction remains fixed and further cracks are considered in directions perpendicular to the original crack direction. Note that for axisymmetric problems, one crack direction is known a priori. The theta or out-of-plane direction is not coupled to the and directions (i.e., no or shear strain/stress exists) and is therefore a known or principal direction.
If we store a scalar value, , for each of the three possible crack directions at a material point, these in combination with the principal directions (eigenvectors or rotation tensor) provide a convenient way to eliminate stress in cracked directions. A value of 1 for indicates that the material point has not cracked in that direction. A value very close to zero (not zero for numerical reasons) indicates that cracking has occurred.
We define a cracking tensor in the cracked orientation as : The rotation tensor is defined in terms of the eigenvectors : This leads to a transformation operator :
is useful for transforming uncracked tensors in the global frame to cracked tensors in the same frame. For example, the cracked stress in terms of the stress is (subscript indicates cracked, local frame, and global frame):
There are two options on how the elasticity tensor is modified to account for the effects of cracking, controlled by the cracked_elasticity_type parameter. If that parameter is set to DIAGONAL, when a crack forms in a given direction the diagonal entry in the local tensor is set to the product of the Young's modulus and for that direction, and the off-diagonal coupling terms that define the interaction between that and the other directions are set to 0. This was historically the way this was handled, but is somewhat problematic because upon cracking the transverse stress due to Poisson's affect is abruptly removed. Alternatively, the FULL option scales down the existing on- and off-diagonal entries in the elasticity tensor by , which scales down the transverse stresses at the same rate as stresses in the crack opening direction, resulting in smoother behavior.
When many material points have multiple cracks, the solution becomes difficult to obtain numerically. For this reason, controls are available to limit the number and direction of cracks that are allowed. Also, there are options to control the amount of shear retention and amount of stress correction during softening, both of which can significantly affect convergence.
Example Input File Syntax
[./elastic_stress]
type = ComputeSmearedCrackingStress
cracking_stress = 1.68e6
softening_models = abrupt_softening
[../]
Input Parameters
- absolute_tolerance1e-05Absolute convergence tolerance for the stress update iterations over the stress change after all update materials are called
Default:1e-05
C++ Type:double
Controllable:No
Description:Absolute convergence tolerance for the stress update iterations over the stress change after all update materials are called
- 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
- combined_inelastic_strain_weightsThe combined_inelastic_strain Material Property is a weighted sum of the model inelastic strains. This parameter is a vector of weights, of the same length as inelastic_models. Default = '1 1 ... 1'. This parameter is set to 1 if the number of models = 1
C++ Type:std::vector<double>
Controllable:No
Description:The combined_inelastic_strain Material Property is a weighted sum of the model inelastic strains. This parameter is a vector of weights, of the same length as inelastic_models. Default = '1 1 ... 1'. This parameter is set to 1 if the number of models = 1
- 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
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
- cracked_elasticity_typeDIAGONALMethod to modify the local elasticity tensor to account for cracking
Default:DIAGONAL
C++ Type:MooseEnum
Controllable:No
Description:Method to modify the local elasticity tensor to account for cracking
- cracking_neg_fraction0The fraction of the cracking strain at which a transition begins during decreasing strain to the original stiffness.
Default:0
C++ Type:double
Controllable:No
Description:The fraction of the cracking strain at which a transition begins during decreasing strain to the original stiffness.
- cycle_modelsFalseAt timestep N use only inelastic model N % num_models.
Default:False
C++ Type:bool
Controllable:No
Description:At timestep N use only inelastic model N % num_models.
- damage_modelName of the damage model
C++ Type:MaterialName
Controllable:No
Description:Name of the damage model
- 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.
- internal_solve_full_iteration_historyFalseSet to true to output stress update iteration information over the stress change
Default:False
C++ Type:bool
Controllable:No
Description:Set to true to output stress update iteration information over the stress change
- max_cracks3The maximum number of cracks allowed at a material point.
Default:3
C++ Type:unsigned int
Controllable:No
Description:The maximum number of cracks allowed at a material point.
- max_iterations30Maximum number of the stress update iterations over the stress change after all update materials are called
Default:30
C++ Type:unsigned int
Controllable:No
Description:Maximum number of the stress update iterations over the stress change after all update materials are called
- max_stress_correction1Maximum permitted correction to the predicted stress as a ratio of the stress change to the predicted stress from the previous step's damage level. Values less than 1 will improve robustness, but not be as accurate.
Default:1
C++ Type:double
Controllable:No
Description:Maximum permitted correction to the predicted stress as a ratio of the stress change to the predicted stress from the previous step's damage level. Values less than 1 will improve robustness, but not be as accurate.
- perform_finite_strain_rotationsTrueTensors are correctly rotated in finite-strain simulations. For optimal performance you can set this to 'false' if you are only ever using small strains
Default:True
C++ Type:bool
Controllable:No
Description:Tensors are correctly rotated in finite-strain simulations. For optimal performance you can set this to 'false' if you are only ever using small strains
- prescribed_crack_directionsPrescribed directions of first cracks
C++ Type:MultiMooseEnum
Controllable:No
Description:Prescribed directions of first cracks
- 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.
- relative_tolerance1e-05Relative convergence tolerance for the stress update iterations over the stress change after all update materials are called
Default:1e-05
C++ Type:double
Controllable:No
Description:Relative convergence tolerance for the stress update iterations over the stress change after all update materials are called
- shear_retention_factor0Fraction of original shear stiffness to be retained after cracking
Default:0
C++ Type:double
Controllable:No
Description:Fraction of original shear stiffness to be retained after cracking
- tangent_operatornonlinearType of tangent operator to return. 'elastic': return the elasticity tensor. 'nonlinear': return the full, general consistent tangent operator.
Default:nonlinear
C++ Type:MooseEnum
Controllable:No
Description:Type of tangent operator to return. 'elastic': return the elasticity tensor. 'nonlinear': return the full, general consistent tangent operator.
- use_interpolated_stateFalseFor the old and older state use projected material properties interpolated at the quadrature points. To set up projection use the ProjectedStatefulMaterialStorageAction.
Default:False
C++ Type:bool
Controllable:No
Description:For the old and older state use projected material properties interpolated at the quadrature points. To set up projection use the ProjectedStatefulMaterialStorageAction.
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
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