Of the 3 idealizations or elements that created the line idealization solves the quickest. It is a 1D element with 6 degrees of freedom. Line idealizations are used when creating frames. The best way to do this is create your frames with the frame generator. This way Nastran will automatically assign a beam idealization to the part and you are then already half way to getting your analysis out.
If you have created only the frame (2D and 3D lines) and do not want to utilise the frame generator you can create 3 types of line elements in Nastran, Bar, Beam and Pipe.
With the line element you can specify the properties of your line element like the area, area factors for shear and stress recovery coefficients. Alternatively you can also specify the cross section.
When selecting the bar line element you have the following shape selections for your cross section.
- Rod
- Tube
- I Beam
- I Beam 1
- Channel
- Channel 1
- Channel 2
- T Shape
- T Shape 1
- T Shape 2
- Cross
- Bar
- Box
- Box 1
- H Shape
- Hexagonal
- Z Shape
- Hat
- Hat 1
For the Beam line element you have the above shapes as well as the following.
- L Shape
Unfortunately you cannot add to those default cross sections in Nastran IN CAD/ Inventor Nastran. If you want a custom cross section profile you need to create one using the frame generator and the Inventor Authoring tools.
A bonus in using the cross section definition is that you can also have a taper on the element i3 the one end is bigger than the other.
