COMSOL 6.2 - Solid–Beam Connection

Add the multiphysics coupling node (

) to create transitions between domains modeled using the Solid Mechanics or Multibody Dynamics interfaces and edges modeled using the Beam interface.

The 2D and 3D versions of the are fundamentally different, and are treated separately below.

Select — or .

Select the interface to couple.

Select the — , , , or .

In first two cases, there is an automatic search for possible adjacent geometrical objects. If you want to modify the selections, select the check box. If you clear it again, the selections will be replaced by the automatic ones.

For a manual selection, select the connected solid boundaries in the section and the corresponding beam points in the section.

Select — , , or . This parameter determines how much of the selected solid boundaries that are actually connected to the beam. The default is that a distance from the beam point having the size of the half the beam section height in each direction is connected. Using connects the entire selected boundaries to the beam. If you select , enter a d. This is used instead of the section height for defining the connection distance.

Select a — or . The version of the coupling only adds constraints to the boundary of the solid, which in general causes local disturbances of the stress field, since the thickness cannot change. When using the coupling, three extra degrees of freedom are added to each beam point. This allows for a more accurate description of the transition, but the model can in some cases become unconstrained if the mesh on the solid is very coarse.

When the connected area is determined by either the or , the connected area is slightly extended by a distance Δ. Select how to determine this — or . For , the tolerance Δ is set to 0.5% of the beam height, which allows for small inaccuracies on for example a curved geometry. By selecting , you can modify the value of Δ.

If the automatic selection is not sufficient, select the check box. Then, select the connected boundaries in the section.

The connected area is slightly extended by the distance Δ. Select how to determine this — or . The option sets the value of the tolerance Δ to 0.5% of section height of the beam. By selecting the option, you can modify the value of the tolerance Δ.

Select the connected solid boundaries in the section and the corresponding beam edges in the section.

Select — , , or . This parameter determines how the coupling treats the determination of the connection distance, used when expressing the coupling between translation and rotation. The default is that a distance equal to half the section height is used. If you select , the connection distance is computed from the geometrical distance between the solid boundary and the beam boundary. For enter a d. This defines the connection distance.

The connected area is slightly extended by a distance Δ. Select how to determine this — or . For , the tolerance Δ is set to 0.5% of the beam height, which allows for small inaccuracies on, for example, a curved geometry. By selecting , you can modify the value of Δ.

Select the — , , , or . For the connections to beam points, there is an automatic search for possible adjacent geometrical objects. If you want to modify the selections, select the check box. If you clear it again, the selections will be replaced by the automatic ones.

Select this when the end of a beam is to be “welded” to part of the face of a solid domain.

If the automatic selection is not sufficient, select the check box. Then, select the connected solid boundaries in the section and select the corresponding beam points in the section.

Select a —, , , or .

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For , all parts on the solid boundary, which are within the default distance from the beam point, are connected. This distance is determined by the cross section properties of the beam. It is contained in the variable beam.re as described in the documentation for The Beam Interface.

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For enter a rc. All parts on the solid boundary, which are within the given distance from the beam point, are connected.

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For enter a Boolean expression in the text field. The beam is connected to the selected solid boundaries, wherever the expression has a nonzero value. The default value is 1, which is equivalent to using the option.

Use this option if you want to model a transition from a beam modeled by solid elements to the same beam modeled using beam elements. It is assumed that the solid part is truncated by a set of boundaries which are perpendicular to the beam axes. No settings other than the selections are needed in this case.

If the automatic selection is not sufficient, select the check box. Then, select the connected solid boundaries in the section and select the corresponding beam points in the section.

The coupling can introduce a set of extra degrees of freedom on the solid boundary for computing the warping displacement over the cross section. Select —, , or , to control this behavior. If is selected, warping will be included, unless the beam cross section is one of the predefined sections or . To explicitly control the behavior, select or .

The warping degrees of freedom should preferably be solved for only once, and separately. If they are solved at the same time as the general problem, you can expect that the solution time increases by a factor of two. For more details, see Beam Point to Solid (3D) in the Structural Mechanics Modeling chapter.

Use this option when you want to model a beam that is parallel to the solid boundary and is “welded” to it.

Select a —, , or .

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Using makes all selected boundaries to be rigidly connected to the point on the beam. This is mainly useful if the boundary has approximately the same shape as the physical size of the beam, such as a rectangle with the same width as a beam flange.

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For , enter a w. All parts on the solid boundary, which are within the given distance from the projection of the beam axis on the solid, are connected. For cases when the beam is asymmetric, that is when the connection distance from the beam axis is not the same in both directions, enter also an d. The positive orientation of the offset is n × t, where n is the outward normal of the solid, and t is the positive orientation of the beam edge.

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For enter a Boolean expression in the text field. The beam is connected to the selected solid boundary, wherever the expression has a nonzero value. The default value is 1, which is equivalent to using the option.

Select this when the end of a beam is to be “welded” to an edge of a solid domain. One important use case is when modeling bolts using beams, and this coupling acts as an abstract bolt head.

Select the connected solid edges in the section and select the corresponding beam points in the section.

Select a —, , , or .

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For , all parts on the solid edges, which are within the default distance from the beam point, are connected. The distance is determined by the cross section properties of the beam. It is contained in the variable beam.re as described in the documentation for The Beam Interface.

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For enter a rc. All parts on the solid edges, which are within the given distance from the beam point, are connected.

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For enter a Boolean expression in the text field. The beam is connected to the selected solid edges, wherever the expression has a nonzero value. The default value is 1, which is equivalent to using the option.