COMSOL 6.2 - Spring Foundation

Select the and its associated spring constant or force using Table 5-21 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.

Table 5-21: Spring Types For the Spring Foundation Feature.
Spring Type	variable	SI units	Geometric Entity Level
Spring constant per unit volume	kV	N/(m⋅m3)	domains (Plate), boundaries (Shell)
Total spring constant	ktot	N/m	domains (Plate), boundaries (Shell, Plate), edges (Shell)
Spring constant per unit area	kA	N/(m⋅m)2	domains (Plate), boundaries (Shell, Plate), edges (Shell)
Spring constant per unit length	kL	N/(m⋅m)	boundaries (Plate), edges (Shell)
Spring constant	kP	N/m	points (Shell, Plate)
Force per volume as function of extension	FV	N/m3	domains (Plate), boundaries (Shell)
Total force as function of extension	Ftot	N	domains (Plate), boundaries (Shell, Plate), edges (Shell)
Force per area as function of extension	FA	N/m2	domains (Plate), boundaries (Shell, Plate), edges (Shell)
Force per length as function of extension	FL	N/m	boundaries (Plate), edges (Shell)
Force as function of extension	FP	N	points (Shell, Plate)

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 , then 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 select and enter the same value for all diagonal elements.

Viscous Damping

Select the using Table 5-22 as a guide. The default option is the default damping type for the type of geometric entity and space dimension, and there are different combinations available based on this. 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 5-22: Damping Types For the Spring Foundation Feature.
Damping Type	variable	SI units	Geometric Entity Level
Damping constant per unit volume	dV	N⋅s/(m⋅m3)	domains (Plate), boundaries (Shell)
Damping constant per unit area	dA	N⋅s/(m⋅m2)	domains (Plate), boundaries (Shell, Plate), edges (Shell)
Total damping constant	dtot	N⋅s/m	domains (Plate), boundaries (Shell, Plate), edges (Shell)
Damping constant per unit length	dL	N⋅s/(m⋅m)	boundaries (Plate), edges (Shell)


	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.

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