COMSOL 6.2 - Edge to Boundary

Add an node to connect a shell edge to a shell boundary in a mesh independent configuration.

This connection is useful in, for example, the following situations:

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You have an imported geometry where there are slits in the geometry.

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A midsurface generation has left slits in the geometry.

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You want to avoid the extra flexibility that would be the effect of connecting at the midsurface. With this type of coupling, you can take she shell thickness into account in a more accurate way.

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You want to model and evaluate a weld. In that case, you can use the flexible version of the coupling, and evaluate the forces in it.

If possible, use the Edge to Edge coupling, which involves fewer approximations. The coupling has the advantage that there is no need for having matching edges in the geometry.

Coordinate System Selection

Select the coordinate system to use for specifying the stiffness in the case of a flexible connection. From the list select from:

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(the standard global coordinate system).

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	For details about the definition of local edge systems, see Local Edge System.

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Any additional user-defined coordinate system.

Face Defining the Orientations

This setting is used in conjunction with and. When the connection is used for an edge which is shared between boundaries, the coordinate system can be ambiguous. Select the boundary which should define the edge system. The default is .


	This section is available only for edges in the Shell interface and is only visible if the selected coordinate system is Local edge system or Shell Local System.

Connection Settings

Select a — or .

For , the coupling between the two parts is rigid in a pointwise manner. Every point on the destination boundary is coupled by a virtual rigid bar to the nearest point on the source edge. This does not imply that the whole edge is rigid.

For , select for both the source and destination sides of the connection the — , (default), or .

For , you supply a stiffness matrix, connecting the corresponding points on the source and destination sides. The stiffness coefficients are given per unit length along the edge. Input fields for the matrices ku,L and kΘ,L are always shown. Select to show input fields for the coupling matrices kuΘ,L and kΘu,L. In 2D axisymmetry, most elements of these matrices are by definition zero. Only elements which can be nonzero are shown; these are elements 13 and 23 for kuΘ,L, and elements 31 and 32 for kΘu,L.

The stiffness relation can be expressed as

Here, f and m are the forces and moments per unit length acting on the destination side, and Δu is the difference between the destination side displacements and the source side displacements. Similarly, ΔΘ is the difference between the destination side rotations and the source side rotations. All vectors are expressed in the selected coordinate system.

Optionally, you can enter a , ρu,L. This can for example be the mass of a not modeled weld.

On the boundary, a strip with a certain width is used for the connection. Select a — or to control the width of the strip. The default is , in which case the thickness of the shell on the source side (the edge) is used as the connection width. By choosing enter the desired width.

The two boundaries are only connected if they are within a certain tolerance from touching each other. The distance is computed including shell thickness and offset. You can modify this tolerance. Select a — or . For , enter the maximum allowable distance or overlap between the boundaries, δ.

Constraint Settings

To display this section, click the button (

) and select in the dialog box. The information in this section i sonly used if is set to .

In the COMSOL Multiphysics Reference Manual:

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Constraint Reaction Terms

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Weak Constraints

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Constraint Settings

Location in User Interface

Context Menus

Ribbon

Physics tab with selected: