Spring Foundation (Rigid Domain)
The Spring Foundation subnode is used to specify a spring or damper connecting the rigid domain to a fixed ground. The spring can act at an arbitrary position in space. A translational spring implicitly contributes also to the moment if it is not applied at the center of mass of a rigid domain. The data that you specify is interpreted in the selected coordinate system.
Location
Select an option from the list: Center of rotation, Centroid of selected entities, or User defined. This is the location where the spring will be attached.
For Center of rotation, the location of the spring is taken as the center of rotation as defined in the parent Rigid Domain node.
For Centroid of selected entities select an Entity levelBoundary, Edge, or Point. The available choices depend on physics interface and geometrical dimension. The spring is attached at the centroid of the selected entities, which do not need to be related to rigid domain itself. As a special case, you can select a single point, and thus attach the spring at that point.
For User defined, enter the Global coordinates of center of rotation, Xc, in the table.
Select the Offset check box to add an optional offset vector to the definition of the location. Enter values for the offset vector Xoffset.
The location used is the sum of the vector obtained from any of the input methods and the offset vector.
Spring
Select a Spring typeSpring constant or Force as function of extension.
When Spring constant is selected, the translational spring matrix can be entered as Isotropic, Diagonal, Symmetric, or Anisotropic. For Isotropic the same spring constant is used in all the diagonal elements of the spring matrix.
When Force as function of extension is selected, enter the force vector Fs. It must be a a function of the built-in variables describing the spring extension. The default value indicates the correct variable name, for example solid.rd1.uspring1_spf1.
Rotational Spring
Select a Spring typeSpring constant or Moment as function of rotation.
When Spring constant is selected, the rotational spring matrix can be entered as Isotropic, Diagonal, Symmetric, or Anisotropic. For Isotropic the same spring constant is used in all the diagonal elements of the spring matrix.
When Moment as function of rotation is selected, enter the moment vector Ms. It must be a a function of the built-in variables describing the spring extension. The default value indicates the correct variable name, for example solid.rd1.thspring1_spf1.
In 2D the Spring constant is only a single scalar, representing the stiffness for rotation around the out-of-plane direction. Similarly, the Moment as function of rotation is a single scalar.
Loss Factor Damping
From the Loss factor type list, select Scalar (Same for all components) or Individual components.
For Scalar (Same for all components) enter a single Loss factor for spring ηu,s, which is used to multiply all values of the spring matrix or spring force vector.
For Individual components select Isotropic, Diagonal, Symmetric, or Anisotropic, then enter values or expressions in the table for the Loss factor for spring ηu,k or ηf based on space dimension. The loss factors act on the corresponding components of the spring matrix or spring force vector. If you select Isotropic, the effect is the same as when you selecting Diagonal and enter the same value for all diagonal elements.
Rotational Loss Factor Damping
All settings in the Rotational Loss Factor Damping section are analogous to the corresponding settings in the Loss Factor section. In 2D, only one scalar loss factor, corresponding to rotation around the out-of-plane axis, is given.
Viscous Damping
Select Isotropic, Diagonal, Symmetric, or Anisotropic, then enter values or expressions for the damping constants du in the table. If you select Isotropic, the effect is the same as when you selecting Diagonal and enter the same value for all diagonal elements.
Viscous Rotational Damping
All settings in the Viscous Rotational Damping section are analogous to the corresponding settings in the Viscous Damping section. In 2D, only one scalar viscous damping, corresponding to rotation around the out-of-plane axis, is given.
Location in User Interface
Context Menus
Solid Mechanics>Rigid Domain>Spring Foundation
Multibody Dynamics>Rigid Domain>Spring Foundation
Shell>Rigid Domain>Spring Foundation
Beam>Rigid Domain>Spring Foundation
Ribbon
Physics tab with Rigid Domain node selected in the model tree:
Attributes>Spring Foundation