Step 4: Specify geometry
Since the geometry, material properties and loading are all symmetric with respect to the horizontal and vertical centerlines, we need to model only a quarter of the plate. We will take the origin of the coordinate system to be at the center of the hole and model only the top right quadrant. We'll create the geometry by creating a square area of side a and subtracting the circular sector of radius r from it.
Create the Square
Main Menu > Preprocessor > Modeling >Create > Areas >Rectangle > By Dimensions
...
Click OK. You should see a square appear in the graphics window.
Create the Circular Sector
Main Menu > Preprocessor > Modeling > Create > Areas > Circle > Partial Annulus
...
This will create and draw the circular sector. You'll see a white line denoting the circular sector.
Subtract Circular Sector from Square
Main Menu > Preprocessor >Modeling > Operate > Booleans > Subtract > Areas
...
If you picked an area incorrectly, you can unpick it by clicking the right mouse button and selecting the area. The cursor changes to a downward arrow during an unpick operation. Right-click to return to pick mode.
Save Your Work
Toolbar > SAVE_DB
Go to Step 5: Mesh geometry