Thin Elastic Layer

Use the node to apply elastic and damping conditions between two parts, either on an interior boundary or on a boundary pair.

By adding the Predeformation subnode, you can prescribe that the spring force is zero at a non-zero spring extension.

The and Spring Foundation nodes are similar, with the difference that a Spring Foundation connects the structural part on which it is acting to a fixed “ground”.

The node is only available with some COMSOL products (see http://www.comsol.com/products/specifications/).

Pair Selection

If this node is selected from the menu, choose the pair on which to apply this condition. An identity pair has to be created first. Ctrl-click to deselect.

Coordinate System Selection

The spring and damping constants are given with respect to the selected coordinate system, with the exception that when the stiffness is specified by , the coordinate system selection is not used.

Spring

Select the and its associated spring constant or force using Table 4-8 as a guide. The default option is the spring type for the type of geometric entity and space dimension, and there are different combinations available based on this.

When the option is of the type ‘force as function of extension’, then the built-in variables describing the spring extension must be used in the expression as described in Springs and Dampers. The spring matrix can be entered as , , , or . For the same spring constant is used in all the diagonal elements of the spring matrix.

When is selected as , the spring stiffness values are computed from material data and layer thickness. From the list, select a pair of elastic properties — , , or Each of these pairs define the elastic properties and it is possible to convert from one set of properties to another according to Table 4-6. For the chosen properties, select from the applicable list to use the value or enter a value or expression. In order to use , you must have assigned a material to the selected boundaries.

Enter a , ds, to specify the physical thickness of the elastic layer.

Table 4-8: Spring Types for the Thin Elastic Layer Feature
Spring Type	variable	SI units	Space Dimension
Total spring constant	ktot	N/m	3D, 2D, and 2D axisymmetric
Spring constant per unit area	kA	N/(m⋅m)2	3D, 2D, and 2D axisymmetric
Spring constant per unit length	kL	N/(m⋅m)	2D
Total force as function of extension	Ftot	N	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
Use material data	N/A	N/A	3D, 2D, and 2D axisymmetric

Loss Factor Damping

From the list, 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 and enter values or expressions in the table for the ηk 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 , the effect is the same as when you selecting and enter the same value for all diagonal elements.

Viscous Damping

Select the using Table 4-9 as a guide. The default option is the default damping type for the space dimension. The damping matrix can be entered as , , , or . For the same viscous constant is used in all the diagonal elements of the damping matrix

Table 4-9: Damping Types For the Thin Elastic Layer Feature
Damping Type	variable	SI units	Space Dimension
Damping constant per unit area	dA	N⋅s/(m⋅m2)	3D, 2D, and 2D axisymmetric
Total damping constant	dtot	N⋅s/m	3D, 2D, and 2D axisymmetric
Damping constant per unit length	dL	N⋅s/(m⋅m)	2D


	You can activate and deactivate this boundary condition by assigning it to a constraint group. See Load Cases in the Structural Mechanics Modeling chapter.

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Springs and Dampers in the Structural Mechanics Modeling chapter.

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Spring Foundation and Thin Elastic Layer in the Structural Mechanics Theory chapter.

Location in User Interface

Context Menus

Ribbon

Physics tab with selected: