Spring-Damper

Use a to model — between two points—an elastic spring, a viscous damper, or both. By adding a Truss interface with this material model, you can add springs and dashpots to any other structural mechanics physics interface.

Spring-Damper

Select a — or .

•

For enter a value for the spring constant k.

•

For enter an expression for the spring force 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 truss.spd1.dl. The default expression is (1[N/m])*truss.spd1.dl, which corresponds to a linear spring with the stiffness 1 N/m.

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

To add loss factor damping, enter a value for the η.

Free Length

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 .

•

For enter a value for

. The free length is computed as

, where l0 is the initial distance between the connection points.

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For enter a value for lf.

Activation Condition

Select a —, , or .

Select the check box to enter a idac. The expression is treated as a boolean expression, so that when it is 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 once 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 truss.spd1.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.

Location in User Interface

Context Menus

Ribbon

Physics tab with selected: