Entities and Numbering
Volumes, Areas, and Lines are features of the solid model. All this really means is that these are entities we use to draw the geometry. These entities are merely an intermediate step between the geometry we want to create, and the Finite-Element representation of that geometry.
Nodes and Elements are the building blocks of the Finite-Element representation. Elements are basically just polygons which divide the larger geometry up into small discrete chunks. Nodes are simply points at the corners of the elements. The Finite-Element Analysis is based on the elements. The areas and lines and volumes we draw really serve no other purpose than to tell the mesher how to organize the elements. This is why, for example, it is critical to transfer boundary conditions applied to lines to the actual elements themselves using the sbctran command.
The following is an example of an array of simple, regular elements. The nodes are represented as black dots.
The following is an example of a simple array of 8-node elements. The additional node in the center of the line segments is particularly useful for structural simulations as the element is given a greater degree of flexibility.
Elements can be a variety of sizes and shapes. Nodes mark off their corners. Remember this picture? Only the left-most nodes are marked, but it's clear where the others belong on these 4-node elements.
Keypoints - I have no idea what they are and I have never used them.
Start a new ANSYS session. Go into the Preprocessor and Create an area. For this example I created a circular area. Right after I hit OK, ANSYS output the following text to the window from which I started ANSYS:
ANSYS treats other entities in the same way. If you know the number of the entity or entities you want to operate on or work with, selecting them is as simple a entering their number into the input box. This leads nicely into our next topic:
Volumes, Areas, and Lines are features of the solid model. All this really means is that these are entities we use to draw the geometry. These entities are merely an intermediate step between the geometry we want to create, and the Finite-Element representation of that geometry.
Nodes and Elements are the building blocks of the Finite-Element representation. Elements are basically just polygons which divide the larger geometry up into small discrete chunks. Nodes are simply points at the corners of the elements. The Finite-Element Analysis is based on the elements. The areas and lines and volumes we draw really serve no other purpose than to tell the mesher how to organize the elements. This is why, for example, it is critical to transfer boundary conditions applied to lines to the actual elements themselves using the sbctran command.
The following is an example of an array of simple, regular elements. The nodes are represented as black dots.
The following is an example of a simple array of 8-node elements. The additional node in the center of the line segments is particularly useful for structural simulations as the element is given a greater degree of flexibility.
Elements can be a variety of sizes and shapes. Nodes mark off their corners. Remember this picture? Only the left-most nodes are marked, but it's clear where the others belong on these 4-node elements.
Keypoints - I have no idea what they are and I have never used them.
How does ANSYS keep track of all these entities?
Well, it uses a numbering system--a very simple one actually.Start a new ANSYS session. Go into the Preprocessor and Create an area. For this example I created a circular area. Right after I hit OK, ANSYS output the following text to the window from which I started ANSYS:
CREATE A CIRCULAR AREA WITH
INNER RADIUS = 0.2000000000
OUTER RADIUS = 0.5000000000
STARTING THETA ANGLE = 0.0000000000E+00
ENDING THETA ANGLE = 37.00000000
OUTPUT AREA = 1
Here ANSYS is showing me the command I had it perform (through my mouse clicks)
and the result of that command, area 1.
I'll create a second area, a
rectangle this time, making sure they overlap--area 2. Now, if I subtract
area 1 from area 2 a new area is created, area 3.
SUBTRACT AREAS
AREA NUMBERS TO BE OPERATED ON = 2
AREAS OPERATED ON WILL BE DELETED
AREA NUMBERS TO BE SUBTRACTED = 1
AREAS SUBTRACTED WILL BE DELETED
OUTPUT AREAS = 3
Areas 1 and 2 no longer exist. Those numbers will be recycled next time
I create a new area.
ANSYS treats other entities in the same way. If you know the number of the entity or entities you want to operate on or work with, selecting them is as simple a entering their number into the input box. This leads nicely into our next topic:
 |
Tutorial Index |
 |
Picking |