Geometry

Overview

The process we'll follow is:

1. Sketch a line representing the undeformed neutral axis of the beam.
2. Turn this "line sketch" into a "line body". Only "bodies" can be meshed in ANSYS.
3. Define the beam cross-section and assign it to the "line body". ANSYS will then use the cross-section geometry to calculate the moment of inertia while forming the beam element stiffness matrices.

Initial settings

In order to make sure the geometry data gets transferred to the Model a couple of steps must be taken; First, right click on Geometry then click on Properties . Under Properties of Schematic A3: Geometry expand Basic Geometry Options and check the box to the right of Line Bodies as seen below.
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Double-click on the geometry button, Image Removed; in the Project Schematic area, which should launch the Design Modeler in ANSYS. A window should pop up asking for units. Units are in meters, so select Meters and press Ok . A folder called A: Static Structural (ANSYS) should be expanded in the tree outline of the Design Modeler; If it is not expanded, then expand it now.
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Proper Orientation

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Line Sketching

First instinct is to make a rectangular solid as a model for our cantilever. This would create 3D elements which would be one way of modeling the beam. Here we will use a different modeling approach using 1D beam elements. In effect, we are only modeling the neutral axis of the beam and calculating its deformation directly. All other results such as bending stress and bending moment are derived from the deformation of the neutral axis.

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The following videos use the legacy geometry engine, DesignModeler. Please see this page of the EdX course for updated instructions using the new geometry engine, SpaceClaim.

Sketch the Midline

<iframe width="560" height="315" src="https://www.youtube.com/embed/Lm9Z_3eMAQc" frameborder="0" allowfullscreen></iframe>

Specify Moment of Inertia

<iframe width="560" height="315" src="https://www.youtube.com/embed/W_QGlwxIza0" frameborder="0" allowfullscreen></iframe>

Check Your Understanding

Select the correct option below.

Consider the case where we replace our square cross-section in ANSYS with a different cross-section that has a lower cross-sectional area but the same moment of inertia. How is the total potential energy of the beam affected?

It:

1. Decreases
2. Stays the same 
3. Increases

Line Body

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Cross Section

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Assign the Cross Section to the Line Body

Now the defined cross section will be assigned to the line body. ANSYS will then use this cross-section to calculate the moment of inertia while forming the element stiffness matrices. First, expand "1 Part, 1 Body" which is located in the Tree Outline. Next, click on Line Body , and there should be a yellow box to the right of Cross Section under the Details of Line Body. Click on the yellow box and select rect1 as seen below.
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Verify Geometry

We can visualize the beam in 3D by getting ANSYS to wrap the cross-section around the line in the display. Click on View > Cross Section Solids, as shown below;
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If you click on the 1 Cross Section , Image Removed, in the Tree Outline and then click on the light blue dot, Image Removed, you should now see a three dimensionally rendered beam in an isometric view. Note that this is merely a visualization; our beam model is only a line.
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At this point, the Design Modeler window can be closed. Then, click on Save.

Go to Step 3: Mesh

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