- cOrder parameter for damage
C++ Type:std::vector<VariableName>
Controllable:No
Description:Order parameter for damage
- uncracked_base_nameThe base name used to calculate the original stress
C++ Type:std::string
Controllable:No
Description:The base name used to calculate the original stress
Compute Cracked Stress
Computes energy and modifies the stress for phase field fracture
Description
This material implements a phase field fracture model that can include anisotropic elasticity tensors, modifying the stress and computing the free energy derivatives required for the model. It works with the standard phase field kernels for nonconserved variables. In the model, a nonconserved order parameter defines the crack, where in undamaged material and in cracked material. Cracked material can sustain a compressive stress, but not a tensile one. evolves to minimize the elastic free energy of the system.
This model takes the stress and Jacobian_mult that were calculated by another material and modifies them to include cracks.
Model Summary
In the model, the uncracked stress is provided by another material. It is decomposed into its compressive and tensile parts using a spectral decomposition The compressive and tensile parts of the stress are computed from postive and negative projection tensors (computed from the spectral decomposition) according to
Free Energy Calculation
The total strain energy density is defined as where is the strain energy due to tensile stress, is the strain energy due to compressive stress, and is a parameter used to avoid non-positive definiteness at or near complete damage. The compressive and tensile strain energies are determined from:
The crack energy density is defined as where is the width of the crack interface and is a parameter related to the energy release rate.
The total local free energy density is defined as
Stress Definition
To be thermodynamically consistent, the stress is related to the deformation energy density according to Since then,
The Jacobian matrix for the stress is where is the Jacobian_mult that was calculated by the constitutive model.
Evolution Equation and History Variable
To avoid crack healing, a history variable is defined that is the maximum energy density over the time interval , where is the current time step, i.e.
Now, the total free energy is redefined as: with Its derivatives are
The evolution equation for the damage parameter follows the Allen-Cahn equation where and .
This equation follows the standard Allen-Cahn and thus can be implemented in MOOSE using the standard Allen-Cahn kernels, TimeDerivative, AllenCahn, and ACInterface. There is now an action that automatically generates these kernels: NonconservedAction. See the PhaseField module documentation for more information.
Example Input File Syntax
[./cracked_stress]
type = ComputeCrackedStress
c = c
kdamage = 1e-6
F_name = E_el
use_current_history_variable = true
uncracked_base_name = uncracked
[../]
Input Parameters
- F_nameE_elName of material property storing the elastic energy
Default:E_el
C++ Type:MaterialPropertyName
Controllable:No
Description:Name of material property storing the elastic energy
- base_nameThe base name used to save the cracked stress
C++ Type:std::string
Controllable:No
Description:The base name used to save the cracked stress
- 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
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.
- finite_strain_modelFalseThe model is using finite strain
Default:False
C++ Type:bool
Controllable:No
Description:The model is using finite strain
- kappa_namekappa_opName of material property being created to store the interfacial parameter kappa
Default:kappa_op
C++ Type:MaterialPropertyName
Controllable:No
Description:Name of material property being created to store the interfacial parameter kappa
- kdamage1e-09Stiffness of damaged matrix
Default:1e-09
C++ Type:double
Controllable:No
Description:Stiffness of damaged matrix
- mobility_nameLName of material property being created to store the mobility L
Default:L
C++ Type:MaterialPropertyName
Controllable:No
Description:Name of material property being created to store the mobility L
- 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.
- use_current_history_variableFalseUse the current value of the history variable.
Default:False
C++ Type:bool
Controllable:No
Description:Use the current value of the history variable.
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