Spring-Damper

) for 2D and 3D components to model — between two points — an elastic spring, a viscous damper, or both.

Select the two points between which the spring or damper is connected.

The settings are similar to the corresponding settings for the Distance Joint but applied to Spring-Damper. There is however one more alternative for both and ; . This is the default option, and then you do the actual selections in the and subnodes. If you make a nondefault choice for or , the corresponding selection subnode will be removed.

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 check box is selected, two subnodes named Source Filter and Destination Filter are added to the node. In these subnodes you can make graphic selections of the objects whose attachments should be shown in the and a lists.

Select a — or .

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For 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 mbd.spd1.dl.

To add viscous damping in a dynamic analysis, enter a value or expression for the c.

The free length is the distance between the connection points when there is no force in the spring. Select an option from the list: or .

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For enter a value for Δl0. The free length is computed as lf = l0 − Δl0, where l0 is the initial distance between the connection points.

Select a — , , or .

Select the check box to enter a idac. The expression is treated as a boolean expression, so that when it evaluated to a nonzero value, the spring or damper is deactivated.

Select the check box if the spring is supposed to be removed permanently from the simulation when the deactivation condition is fulfilled for the first time.

As an example, if the spring should break at a certain extension, you can write an expression like mbd.spd2.dl>0.12[m], and select the check box. If the check box is not selected, the spring would become active again when its connection points come close enough to each other.