# Compute Small Strain

Compute a small strain.

## Description

The material ComputeSmallStrain is designed for linear elasticity problems, which calculates the small, total strain. This material is useful for verifying material models with hand calculations because of the simplified strain calculations.

Linearized small strain theory assumes that 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) For more details on the linearized small strain assumption and derivation, see a Continuum Mechanics text such as Malvern (1969) or Bower (2009), specifically Chapter 2.

Total strain theories are path independent: in MOOSE, path independence means that the total strain, from the beginning of the entire simulation, is used to calculate stress and other material properties. Incremental theories, on the other hand, use the increment of strain at timestep to calculate stress. Because the total strain formulation ComputeSmallStrain is path independent, no old values of strain or stress from the previous timestep are stored in MOOSE. For a comparison of total strain vs incremental strain theories with experimental data, see Shammamy and Sidebottom (1967).

## Example Input File Syntax

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

[Modules/TensorMechanics/Master]
[./block1]
strain = SMALL #Small linearized strain, automatically set to XY coordinates
add_variables = true #Add the variables from the displacement string in GlobalParams
[../]
[]

(modules/tensor_mechanics/tutorials/basics/part_1.1.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 ComputeSmallStrain material in an input file.

[./strain]
type = ComputeSmallStrain
[../]


## 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