Page 81 - Using ANSYS for Finite Element Analysis A Tutorial for Engineers

68 • Using ansys for finite element analysis

3.3 solid modeling

The purpose of using a solid model is to relieve you of the time-consuming
task of building a complicated finite element model by direct generation.
Let us take a brief look at some of the solid modeling and meshing opera-
tions that you can use to speed up the creation of your final analysis model.
Building your model from the bottom up: Keypoints, the points
that define the vertices of your model, are the lowest-order solid model
entities. If, in building your solid model, you first create your keypoints,
and then use those keypoints to define the higher-order solid model enti-
ties (that is, lines, areas, and volumes), you are said to be building your
model from the bottom up. Keep in mind that models built from the bottom
up are defined within the currently active coordinate system.
Building your model from the top down: The ANSYS program also
gives you the ability to assemble your model using geometric primitives,
which are fully defined lines, areas, and volumes. As you create a prim-
itive, the program automatically creates all the lower entities associated
with it. If your modeling effort begins with the higher primitive entities,