) for 2D and 3D components to model — between two points — an elastic spring, a viscous damper, or both.) for 2D and 3D components to model — between two points — an elastic spring, a viscous damper, or both.|
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There is one other option: Prescribed displacement.
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Using Prescribed displacement, it is possible to connect the spring to another physics interface. In order to do that, you can to enter expressions using Nonlocal Couplings defined in the Definitions node for a component.
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When the Spring type is set to Matrix, the rotation of the source and the destination (Θs and Θd) are determined by availability of rotational degrees of freedom. If the physics interface itself has rotational degrees of freedom, these will be used in a point selection. For all physics interfaces, irrespective if they have rotational degrees of freedom or not, a connection to an attachment or rigid body type object will provide a rotation.
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When the Spring-Damper node is used in the Multibody Dynamics interface, there is one more option: Use selection filter.
In large models, the list of available attachments can become very long. You can then create geometric filters to narrow down the search. When the Use selection filter check box is selected, two subnodes named Source Filter and Destination Filter are added to the Spring-Damper node. In these subnodes you can make graphic selections of the objects whose attachments should be shown in the Source and a Destination lists.
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For Force as function of extension enter an expression for Fs. The expression must be a function of the extension of the spring. The built-in variable for the spring extension has the form <physicsName>.<SpringNodeTag>.dl, for example solid.spd1.dl.
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Under Spring constants, enter the stiffness matrices defining the elastic connection between the source and destination. Input fields for the matrices ku and kΘ are always shown. Select Translational-rotational coupling to show input fields for the coupling matrices kuΘ and kΘu. In 2D, most elements of these matrices are by definition zero. Only elements which can be nonzero are shown; these are elements 13 and 23 for kuΘ, and elements 31 and 32 for kΘu.
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Under Damping coefficients, enter the damping matrices defining the viscous connection between the source and destination. Input fields for the matrices cu and cΘ are always shown. Select Translational-rotational coupling to show input fields for the coupling matrices cuΘ and cΘu. In 2D, most elements of these matrices are by definition zero. Only elements which can be nonzero are shown; these are elements 13 and 23 for cuΘ, and elements 31 and 32 for cΘu.
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By default, the relative displacement between source and destination is computed as Δu = ud - us. In some cases, however, it can be more reasonable to also include displacements resulting from a rigid body type rotation. If Include rotational contribution in displacement is selected, an additional term is added to the expression for the relative displacement. It describes the additional displacement due to the rotation of the destination if the source and destination were connected by a rigid bar element.
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For Specify initial extension enter a value for Δl0. The free length is computed as lf = l0 − Δl0, where l0 is the initial distance between the connection points.
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