Spring Material

The spring constants and loss factors are given with respect to the selected coordinate system.

Select the and its associated spring constant or force using Table 4-8 as a guide.

Use the built-in variables for the thin layer extension for the options , , or . The names are <item>.uelt1, <item>.uelt2, and <item>.ueln, where <item> is the name of the Thin Layer node (e.g. solid.tl1), and t1, t2, and n are the coordinate names of the local boundary system.

The spring constants can be entered as , , or . For the same spring constant is used in all the diagonal elements of the spring matrix.

Table 4-8: Spring Types for the Spring Material Feature
Spring Type	variable	SI units	Space Dimension
Spring constant per unit area	kA	N/(m⋅m2)	3D, 2D, and 2D axisymmetric
Spring constant per unit length	kL	N/(m⋅m)	2D
Total spring constant	ktot	N/m	3D, 2D, and 2D axisymmetric
Force per area as function of extension	FA	N/m2	3D, 2D, and 2D axisymmetric
Force per length as function of extension	FL	N/m	2D
Total force as function of extension	Ftot	N	3D, 2D, and 2D axisymmetric

Enter the of the thin elastic layer — , , or . For thin layers on 2D geometries, it is also possible to enter the ρL.

Geometric Nonlinearity

The settings in this section affect the behavior of the Spring Material in a geometrically nonlinear analysis.

If a study step is geometrically nonlinear, the default behavior is to use a large strain formulation in all domains. Select the check box to always use a small strain formulation, irrespective of the setting in the study step.

Constraint Settings

To display this section, click the button (

) and select in the dialog box. For more information about this section, see Constraint Settings in the COMSOL Multiphysics Reference Manual.

Damping

From the list, select or .

When choosing , select or .

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For enter a single ηs, which is used to multiply all values of the spring matrix or spring force vector.

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For select , , or , then enter values or expressions for the ηk. The loss factors act on the corresponding components of the spring matrix or spring force vector. If you select , the effect is the same as when you select and enter the same value for all diagonal elements.

When choosing , enter the ηb and the ηv.