# Compute Incremental Small Strain

Compute a strain increment and rotation increment for small strains.

## Description

The material ComputeIncrementalSmallStrain is designed for linear elasticity problems formulated within an incremental framework. As with ComputeSmallStrain, this material is useful for verifying material models with hand calculations because of the simplified strain calculations. As in the small strain material, the incremental small strain class assumes the gradient of displacement with respect to position is much smaller than unity, and the squared displacement gradient term is neglected in the small strain definition to give: (1) As the class name suggests, ComputeIncrementalSmallStrain is an incremental formulation. The stress increment is calculated from the current strain increment at each time step. In this class, the rotation tensor is defined to be the rank-2 Identity tensor: no rotations are allowed in the model. Stateful properties, including strain_old and stress_old, are stored. This incremental small strain material is useful as a component of verifying more complex finite incremental strain-stress calculations.

## Example Input File Syntax

The incremental small strain calculator can be activated in the input file through the use of the TensorMechanics Master Action, as shown below.

[./TensorMechanics]
[./Master]
[./all]
strain = SMALL
incremental = true
eigenstrain_names = eigenstrain
generate_output = 'strain_xx strain_yy strain_zz'
[../]
[../]
[../]

(modules/tensor_mechanics/test/tests/thermal_expansion/constant_expansion_coeff.i)
note:Use of the Tensor Mechanics Master Action Recommended

The TensorMechanics Master Action is designed to automatically determine and set the strain and stress divergence parameters correctly for the selected strain formulation. We recommend that users employ the TensorMechanics Master Action whenever possible to ensure consistency between the test function gradients and the strain formulation selected.

Although not recommended, it is possible to directly use the ComputeIncrementalSmallStrain material in the input file.

[./small_strain]
type = ComputeIncrementalSmallStrain
eigenstrain_names = 'eigenstrain1 eigenstrain2'
[../]

(modules/tensor_mechanics/test/tests/thermal_expansion/multiple_thermal_eigenstrains.i)

## Input Parameters

• displacementsThe displacements appropriate for the simulation geometry and coordinate system

C++ Type:std::vector

Options:

Description:The displacements appropriate for the simulation geometry and coordinate system

### Required Parameters

• global_strainOptional material property holding a global strain tensor applied to the mesh as a whole

C++ Type:MaterialPropertyName

Options:

Description:Optional material property holding a global strain tensor applied to the mesh as a whole

• 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

• eigenstrain_namesList of eigenstrains to be applied in this strain calculation

C++ Type:std::vector

Options:

Description:List of eigenstrains to be applied in this strain calculation

• volumetric_locking_correctionFalseFlag to correct volumetric locking

Default:False

C++ Type:bool

Options:

Description:Flag to correct volumetric locking

• 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

• 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.

• enableTrueSet the enabled status of the MooseObject.

Default:True

C++ Type:bool

Options:

Description:Set the enabled status of the MooseObject.

• 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