COMSOL 6.2 - Section Forces

Section Forces

Add a node to compute the integrated section forces for a cross section in a solid. The cross section can consist of more than one boundary, but all the selected boundaries must be planar and located in the same plane. The section forces are computed in a local coordinate system. The details are described under Coordinate System Selection below.

The local section forces are denoted as follows:

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N — Axial force

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T1 — Shear force along first local axis

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T2 — Shear force along second local axis

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Mt — Twisting moment

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M1 — Bending moment around first local axis

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M2 — Bending moment around second local axis

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The section forces will be shown in an evaluation group, named . Optionally, you can also generate two plot groups showing the section forces as arrows.

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When a node has been added or modified, you do not need to compute a new solution. It is sufficient to perform an (

) to make the variables for the new section forces available.

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Note that when you add a node after solving a study, then neither the evaluation group nor the plots will be generated.

Cut Plane Selection

Select the boundaries that define the cross section over which the section forces are to be computed. As a default, it is assumed that the cross section is contiguous. This assumption can be relaxed by selecting the check box.

Coordinate System Selection

Select a coordinate system that defines the orientations of the section forces. Only boundary systems with constant axis directions can be selected. The orientation of the local axes are defined as follows:

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The axial force and twisting moment are positive in the direction of the boundary system normal. For an external boundary, this is by default the outward normal. For an internal boundary, you can use the subnode under a to control the orientation.

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If the check box is cleared, the first local axis defining the section forces is the same the first in-plane direction of the selected coordinate system.

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If the check box is selected, only the normal orientation of the boundary system is used. The first local axis is taken as the inward normal from the symmetry plane into the structure.

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The second in-plane direction is determined by the cross product

Symmetry Plane Selection

This section is only visible if the check box is selected. In that case, select one boundary in the symmetry plane, in order to identify its location and orientation. The symmetry plane should be orthogonal to the cut plane.

Cut Plane

Select the check box for the case that the cross section is defined by boundaries that are not all adjacent to each other. As a default, this situation will generate a warning message, and no results are computed.

Select the check box if the section forces are to be computed for a cross section for which only one half is modeled due to symmetry. When selected, choose a — or , matching the type of symmetry conditions being used. Also, you need to select a boundary in the symmetry plane in the section.

Using a symmetry plane has the following effects:

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The orientation of the section forces are controlled by the orientation of the symmetry plane, as described under Coordinate System Selection.

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The center of gravity of the section is assumed to be located in the symmetry plane.

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Section forces will be doubled, so that the value for the complete section is obtained.

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Some of the section forces are set to zero, is dictated by the type of symmetry.