# 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
[../]

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

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

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

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

## Input Parameters

• 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

Options:

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.

• apparent_creep_strainapparent_creep_strainname of the apparent creep strain (defined by a LinearViscoelasticityBase material)

Default:apparent_creep_strain

C++ Type:std::string

Options:

Description:name of the apparent creep strain (defined by a LinearViscoelasticityBase material)

• elasticity_tensor_invelasticity_tensor_invname of the real compliance tensor (defined by a LinearViscoelasticityBase material)

Default:elasticity_tensor_inv

C++ Type:std::string

Options:

Description:name of the real compliance tensor (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

Options:

Description:name of the apparent elasticity tensor (defined by a LinearViscoelasticityBase material)

• 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