# Compute Eigenstrain

Computes a constant Eigenstrain

## Description

The class ComputeEigenstrain allows the user to specify a constant value of an eigenstrain for a simulation. The eigenstrain is added to the mechanical strain, which can be elastic or inelastic, before computing the corresponding stress measure: (1)

Eigenstrain is the term given to a strain which does not result directly from an applied force. Chapter 3 of Qu and Cherkaoui (2006) describes the relationship between total, elastic, and eigen- strains and provides examples using thermal expansion and dislocations. Eigenstrains are also referred to as residual strains, stress-free strains, or intrinsic strains; translated from German, Eigen means own or intrinsic in English. The term eigenstrain was introduced by Mura (1982).

Based on the number and values of constants provided as the argument to the eigen_base parameter, ComputeEigenstrain will build an isotropic, symmetric, or skew-symmetric Rank-2 eigenstrain tensor.

## Example Input File Syntax

[./eigen]
type = ComputeEigenstrain
eigenstrain_name = eigen_true
eigen_base = '1e-3 1e-3 1e-3 0 0 0'
[../]
(modules/tensor_mechanics/test/tests/visco/gen_kv_driving.i)

## Input Parameters

• eigen_baseVector of values defining the constant base tensor for the Eigenstrain

C++ Type:std::vector

Options:

Description:Vector of values defining the constant base tensor for the Eigenstrain

• eigenstrain_nameMaterial property name for the eigenstrain tensor computed by this model. IMPORTANT: The name of this property must also be provided to the strain calculator.

C++ Type:std::string

Options:

Description:Material property name for the eigenstrain tensor computed by this model. IMPORTANT: The name of this property must also be provided to the strain calculator.

### Required Parameters

• computeTrueWhen false, MOOSE will not call compute methods on this material. The user must call computeProperties() after retrieving the Material via MaterialPropertyInterface::getMaterial(). Non-computed Materials are not sorted for dependencies.

Default:True

C++ Type:bool

Options:

Description:When false, MOOSE will not call compute methods on this material. The user must call computeProperties() after retrieving the Material via MaterialPropertyInterface::getMaterial(). Non-computed Materials are not sorted for dependencies.

• 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

Options:

Description:Optional parameter that allows the user to define multiple mechanics material systems on the same block, i.e. for multiple phases

• 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

• prefactor1Name of material defining the variable dependence

Default:1

C++ Type:MaterialPropertyName

Options:

Description:Name of material defining the variable dependence

### Optional 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

• 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

## References

1. Toshio Mura. General theory of eigenstrains. In Micromechanics of Defects in Solids, pages 1–62. Springer, 1982.[BibTeX]
2. Jianmin Qu and Mohammed Cherkaoui. Fundamentals of micromechanics of solids. Wiley Online Library, 2006.[BibTeX]