Use the Rigid Body Contact node (
) to model structural contact between rigid bodies. When two surfaces are in contact, one is considered to be the source and the other the destination. The source must either be a rigid sphere or a rigid cylinder in 3D. The destination can be one of four types in 3D: a rigid sphere, a rigid cylinder, a planar shape, or an arbitrary shape. In 2D, the source must be a rigid circle. The destination can be either a rigid circle or an arbitrary shape.
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When a Rigid Body Contact node is present in your model, stationary and time-dependent studies are geometrically nonlinear. The Include geometric nonlinearity check box in the study step Settings window is selected and cannot be cleared.
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This section shows a sketch of the rigid body contact for different settings in the Source and
Destination sections. The sketch highlights the source center, the source radius, the destination center, the destination radius, the distance between source center and destination contact point, and the gap.
Specify the Shape of the source. The available choices are
Spherical and
Cylindrical in 3D, and
Circular in 2D.
From the Source list, select a
Rigid Material node available in the Multibody Dynamics interface. The default value is
None.
Use Shape parameters to define geometry parameters of the selected
Rigid Material in the
Shape setting
. The default value is
From geometry. This automatically calculates the radius, axis (for
Cylindrical source in 3D)
and the center of the source object.
By setting the value of Shape parameters to
User defined, you can manually input the geometry parameters. Enter the radius of the
Source rigid body using the
Radius input. Use the
Axis input to enter the direction vector of the axis of the source. This option is available only when
Shape is set to
Cylindrical. To set the axis of the source cylinder, select an option from the list —
Specify direction or
Select a parallel edge.
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For Specify direction enter a value or expression for es0. The default is (1, 0, 0).
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For Select a parallel edge an edge can be selected in the Source Axis subnode, which is added automatically. The vector from the first to the last end of the edge is used to define the source axis. Any edge in the model can be used. Select the Reverse direction check box to reverse the direction of the source axis.
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Select the Center —
Centroid of source,
Centroid of selected entities, or
User defined.
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For User defined enter the global coordinates of the center Xs.
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For Centroid of selected entities select an Entity level — Boundary, Edge (for 3D components), or Point. When selected, a Source Point: Boundary, Source Point: Edge, or Source Point: Point subnode is added.
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If the Shape is set to
Cylindrical (3D), the
Use finite length input is available. Select this, if the source cylinder is assumed to be of finite length, and enter the length of the source rigid cylinder using the
Length input.
Specify the Shape —
Spherical,
Cylindrical,
Planar, or
Arbitrary in 3D.
In 2D, the available options are
Circular,
Planar, and
Arbitrary.
The option Spherical is available only if source
Shape is set to
Spherical. Choose this to model structural contact between two rigid bodies of spherical shape in 3D. Similarly, by setting
Shape to
Circular in 2D,
you can model the structural contact between two circular rigid bodies. Similarly, choose
Cylindrical to model structural contact between either a rigid sphere or a cylinder and a rigid cylinder in 3D.
If the Shape is set to
Spherical (3D),
Cylindrical (3D)
or
Circular (2D), a
Destination list is available. Select a
Rigid Material, different from the one selected as
Source. The default value is
None.
Use Shape parameters to input geometry parameters of the selected
Rigid Material in
Shape. The default value is
From geometry. This automatically calculates the radius, axis (for a
Cylindrical source in 3D
) and the destination’s center.
By setting the value of Shape parameters to
User defined, you can manually input the geometry parameters of destination. Enter the radius of the
Destination rigid body using the
Radius input. Use the
Axis input to enter the direction vector of the axis of destination rigid body. This option is available only when
Shape is set to
Cylindrical. To set the axis of the destination cylinder, select an option from the list —
Specify direction or
Select a parallel edge.
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For Specify direction enter a value or expression for ed0. The default is (1, 0, 0).
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For Select a parallel edge an edge can be selected on the Destination Axis subnode, which is added automatically. The vector from the first to the last end of the edge is used to define the destination axis. Any edge in the model can be used. Select the Reverse direction check box to reverse the direction of the destination axis.
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Select the Center —
Centroid of destination,
Centroid of selected entities, or
User defined.
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For User defined also enter the global coordinates of the center Xd.
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For Centroid of selected entities select an Entity level — Boundary, Edge (3D components), or Point. When selected, a Destination Point: Boundary, Destination Point: Edge, or Destination Point: Point subnode is added.
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If the Shape is set to
Cylindrical (3D), the check box
Use finite length is available. Select this, if the destination cylinder is assumed to be of finite length. Enter the length of the
Destination rigid cylinder using the
Length input.
Select the check box Use inside boundaries for contact if the location of the source is inside the destination. In this case, the inner boundaries of the destination are used for the gap distance and contact force calculations.
If the Shape is set to
Planar, you can select a destination boundary for the contact in the section
Boundary Selection, Destination. Choose
Planar to model the contact between a rigid sphere or a rigid cylinder and a planar surface of infinite size. You can select only one boundary in the section
Boundary Selection, Destination, and this boundary should attach to a rigid body modeled using a
Rigid Material.
If the Shape is set to
Arbitrary, you can select a set of destination boundaries for the contact in the section
Boundary Selection, Destination. These boundaries do not necessarily need to be part of any
Rigid Material nodes. The boundary selection can be specified for 3D and 2D models.
Under Formulation, you select the algorithm used to compute the contact. Select
Penalty or
Penalty, dynamic (default).
The Penalty, dynamic method is intended to be used in time-dependent studies to model dynamic contact.
Select the type of Penalty factor control —
Automatic or
User defined.
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Automatic provides predefined values for the penalty factor. This value is multiplied by a Penalty factor multiplier fp, which can be changed. The default value as 1.
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For User defined, enter a Penalty factor pn. The default value is (1e10[N/m^2])*mbd.diag, where mbd.diag is the diagonal of the bounding box of the geometry.
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Select the type of Penalty factor control —
Automatic,
Viscous only, or
User defined. The settings are the same as for the standard penalty method, except for the
Viscous only option. By selecting
Viscous only, the stiffness terms of the penalty contact are omitted from the formulation.
Select the type of Viscous penalty factor control —
Automatic or
User defined. For
Automatic, enter a value for the
Characteristic time τn. This value can be used as a multiplier for the viscous penalty factor, but should as a rule-of-thumb be in the same order of magnitude as the duration of the contact event. When
User defined is selected, enter the
Viscous penalty factor pnv. The default value is
(1e10[N/m^2])*mbd.diag)*1[ms], where
mbd.diag is the diagonal of the geometry’s bounding box.
When Formulation is set to
Penalty, dynamic, select
Compute viscous contact dissipation to compute and store the energy dissipated by the viscous contact. This adds a global dependent variable with an ODE in order to integrate the dissipated energy.
Physics tab with Multibody Dynamics selected:
