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Section cuts are important for aerospace structures. They are used for analysis and optimization of a built-up beam or entire structure cross section to required EI and GJ values. Calculate cross-section stiffnesses, center of stiffness, and shear center. Apply minimum values that are enforced when sizing. Report summation of “built up” section cut loads, per loadcase. Read more here.
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Section Cuts are organized in the Structures Tree. They do not live within Structures, though, as a single cut can contain Zones from multiple Structures.
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Section Cuts are defined by a plane, a coordinate system, and FEM elements.
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Elements must be selected on the Section Cut to calculate section properties.
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The Zones contained in the Section Cut must have Sizing results for section properties to be calculated.
Creation of Section Cuts is initiated with the Section Cut button on the Structures tab of the Ribbon. This will open an empty Section Cut form.
Create a Single Section Cut
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Name the Section Cut - Enter a name in the field at the top of the Section Cut form.
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(Option A): Direct Input of Section Cut Position and Orientation - If the placement of the section cut is known in advance, the position and orientation of the Section Cut can be defined explicitly. The Section Cut is uniquely defined by an origin (point) and two unit vectors, as described below.
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Origin: This point is defined in the global coordinate system.
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Normal: This unit vector is oriented normal to the Section Cut. The button next to this input can be used to reverse the vector.
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Horizontal: This unit vector lies in the Section Cut plane and defines the horizontal axis of the Section Cut. The button next to this input can be used to reverse the vector.
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Vertical: This vector is automatically calculated from the cross product of the normal and horizontal vector, and also lies in the plane of the Section Cut. The button next to these fields can be used to swap the horizontal and vertical vectors.
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Both the normal and horizontal vector can be input as a vector of any magnitude. However, the vectors will be normalized when "Apply" is clicked.
(Option B): Draw a Section Cut - A faster, but less precise, route for creating a Section Cut is to use the "draw section cut" button on the form, shown below.
Once this button is clicked, they must click twice in the Viewport to define a cut line drawn between the two points. The drawing operation can be canceled by clicking the button again or pressing the Esc key. The drawn Section Cut will have the following approximate orientation:
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Origin: Located normalized center of area of the cross-section (not accounting for thicknesses).
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Normal: Located by the cross product of the horizontal and vertical vectors.
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Horizontal: Aligned with the vector created from the 1st click to the 2nd click location, then rotated to align with the largest dimension of the Section Cut.
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The vectors can be manually modified after the Section Cut has been drawn.
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Select Elements to Include in the Section Cut - The element selection defines the geometry contained within the Section Cut. The selection is initiated by clicking the "Element IDs" drop-down on the form.
Once the selection field is opened, elements can be selected through any method described in Selection Overview. Alternatively, the user can quickly select all elements that pass through the Section Cut by clicking the "Select Intersecting" button. This will automatically populate the Element IDs field.
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Any elements selected before the Section Cut form was opened will be automatically included in the element selection list on the form.
Create Multiple Section Cuts Automatically
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Define a Path for the Origins of the Cuts to Follow - Use the dropdown menu to select the method of path definition:
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Start & End Points: Requires the user to input coordinates for - OR- manually select the start and end points - between which Section Cuts will be created. This option also requires a spacing value between each cut.
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Start Point & Direction: Requires the user to input a starting point and corresponding vector direction - along which Section Cuts will be created. This option requires BOTH the spacing value between each cut and the number of desired cuts.
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CAD Curve: Requires the user to select a CAD curve on which Section Cuts will be created. Define both the offset (if desired) of the cut plane from the CAD curve and the space between each cut.
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Define the Normal and Horizontal Directions of the Cuts - Select between supplying a path (and allowing the cuts to be created tangent to the curve), or coordinate directions for both normal and horizontal directions. Select the coordinate system icon next to either vector field to define the vector with respect to a choice between Global Axis, FEM Coordinate System, Global Points, FEM Nodes, a CAD Edge, or User Defined Points.
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Choose How Member Elements are Chosen for Each Cut - Use the dropdown to choose between:
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Auto-Intersect: Allow HyperX to auto-detect elements that cross the defined cut planes and add them to their respective Section Cuts.
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Selection: Manually select the elements associated with each cut.
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Click 'Create'.
To edit a Section Cut, right-click on the section cut in the Structure Tree and choose "Edit" from the menu.
Mend an Open Section
In some cases, the section defined by the cut plane may not be a completely closed section - an example of which is shown below. This could be the result of user-element-selection error, FEM elements not being modeled for an entire section or the like. If this is the case, HyperX has a 'mapping' feature that can be used to mend (or close) an open section.
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Select the 'map point' button on the top right corner of the Section Cut Display.
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Using the Section Cut display, select the first point - i.e. the point that needs to be mapped.
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Using the Section Cut display, select the second point - i.e. the point that you are mapping to so the section will close.
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Select the green check-mark to confirm the mapping.
To delete a Section Cut, right-click on the corresponding node in the Structure Tree and choose "Delete" from the menu.