# Displacement About Axis

Implements a boundary condition that enforces rotationaldisplacement around an axis on a boundary

## Description

The boundary condition class DisplacementAboutAxis applies a rotating displacement to the specified mesh surface according to the user defined rotation function. The boundary condition is always applied to the displaced mesh. The rotation function can be given in either radians or in angles, and an axis of rotation can be specified with the axis_origin and axis_direction parameters.

The rotating displacement value at the current node is calculated according to Eq. (1): (1) where is the translation matrix for axes of rotation not centered at the coordinate system origin, and , , and are rotation matrices about the , , and coordinate system axes, respectively.

## Example Input File Syntax

[./top_x]
type = DisplacementAboutAxis
boundary = 2
function = rampConstantAngle
angle_units = degrees
axis_origin = '10. 10. 10.'
axis_direction = '0 -1.0 1.0'
component = 0
variable = disp_x
[../]

(modules/tensor_mechanics/test/tests/torque_reaction/torque_reaction_cylinder.i)

A Function is required to prescribe the rate of the DisplacementAboutAxis boundary condition application to the mesh. Note that the name of the Function is used as the argument for the function input parameter in the DisplacementAboutAxis block.

[./rampConstantAngle]
type = PiecewiseLinear
x = '0. 1.'
y = '0. 1.'
scale_factor = 0.1
[../]

(modules/tensor_mechanics/test/tests/torque_reaction/torque_reaction_cylinder.i)

## Input Parameters

• functionThe function providing the angle of rotation.

C++ Type:FunctionName

Options:

Description:The function providing the angle of rotation.

• angle_unitsThe units of the angle of rotation. Choices are:degrees radians

C++ Type:MooseEnum

Options:degrees radians

Description:The units of the angle of rotation. Choices are:degrees radians

• axis_directionDirection of the axis of rotation

C++ Type:libMesh::VectorValue

Options:

Description:Direction of the axis of rotation

• componentThe component for the rotational displacement

C++ Type:int

Options:

Description:The component for the rotational displacement

• variableThe name of the variable that this boundary condition applies to

C++ Type:NonlinearVariableName

Options:

Description:The name of the variable that this boundary condition applies to

• 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

• axis_originOrigin of the axis of rotation

C++ Type:libMesh::VectorValue

Options:

Description:Origin of the axis of rotation

### Required Parameters

• save_inThe name of auxiliary variables to save this BC's residual contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

C++ Type:std::vector

Options:

Description:The name of auxiliary variables to save this BC's residual contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

• diag_save_inThe name of auxiliary variables to save this BC's diagonal jacobian contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

C++ Type:std::vector

Options:

Description:The name of auxiliary variables to save this BC's diagonal jacobian contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

### Optional 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

• use_displaced_meshTrueWhether 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:True

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.

### Advanced Parameters

• vector_tagsresidualThe tag for the vectors this Kernel should fill

Default:residual

C++ Type:MultiMooseEnum

Options:nontime time residual

Description:The tag for the vectors this Kernel should fill

• extra_vector_tagsThe extra tags for the vectors this Kernel should fill

C++ Type:std::vector

Options:

Description:The extra tags for the vectors this Kernel should fill

• matrix_tagssystem timeThe tag for the matrices this Kernel should fill

Default:system time

C++ Type:MultiMooseEnum

Options:nontime system time

Description:The tag for the matrices this Kernel should fill

• extra_matrix_tagsThe extra tags for the matrices this Kernel should fill

C++ Type:std::vector

Options:

Description:The extra tags for the matrices this Kernel should fill