There are two methods to use ANSYS. The first is by means of the graphical user interface or GUI. This method follows the conventions of popular Windows- and X-Windows-based programmes. The GUI method is exclusively used in this book.

The second is by means of command files. The command file approach has a steeper learning curve for many, but it has the advantage that the entire analysis can be described in a small text file, typically in fewer than 50 lines of commands. This approach enables easy model modifications and has minimal file space requirements.

The ANSYS environment contains two windows: the Main Window and an Output Window. Within the Main Window, there are five divisions (see Fig. 2.1).

1. 1. The Utility Menu [A] contains functions that are available throughout the ANSYS session, such as file controls, selections, graphic controls, and parameters.
2. 2. The Input Line [B] shows programme prompt messages and allows the user to type in commands directly.
3. 3. The Toolbar [C] contains push buttons that execute commonly used ANSYS commands. More push buttons can be made available if desired.
4. 4. The Main Menu [D] contains the primary ANSYS functions, organised by preprocessor, solution, general postprocessor, and design optimiser. It is from this menu that the vast majority of modelling commands are issued.
5. 5. The Graphics Window [E] is where graphics are shown and graphical picking can be made. It is here where the model in its various stages of construction and the ensuing results from the analysis can be viewed.

The Output Window, shown in Fig. 2.2, displays text output from the programme, such as listing of data. It is usually positioned behind the Graphics Window and can be brought to the front if necessary.

2.2.2 Saving and restoring jobs

It is good practice to save the model at various stages during its creation. Very often, the stage in the modelling is reached where things have gone well, and the model ought to be saved at this point. In that way, if mistakes are made later on, it will be possible to return to this point.

To save the model, from the ANSYS Utility Menu, select File → Save as Jobname.db.

The model will be saved in a file called Jobname.db, where Jobname is the name that was specified in the Launcher when ANSYS was first started. It is a good idea to save the job at different times throughout the building and analysis of the model, to back up the work in case of a system crash or other unforeseen problems.

Alternatively, select File → Save as. In response to the second option, the frame shown in Fig. 2.3 is produced.

Select the [A] appropriate drive and [B] give the file a name. Clicking the [C] OK button saves the model as a database with the name given.

Frequently there is a need to start up ANSYS and recall and continue a previous job. There are two methods to do this:

1. 1. Using the Launcher: (i) In the ANSYS Launcher, select Interactive and specify the previously defined jobname; (ii) When ANSYS is running, select Utility Menu: File: Resume Jobname.db. This will restore as much of the database (geometry, loads, solution, etc.) as was previously saved.
2. 2. Start ANSYS and select from the Utility Menu File → Resume from, then click on the job from the list that appears. Fig. 2.4 shows the resulting frame.

Select the [A] appropriate file from the list and click the [B] OK button to resume the analysis.

2.2.3 Organisation of files

A large number of files are created when ANSYS is run. If ANSYS is started without specifying a jobname, the name of all files created will be File.⁎, where the ⁎ represents various extensions described below. If a jobname is specified, say Beam, then the created files will all have the file prefix, Beam again with various extensions:

• beam.db—database file (binary). This file stores the geometry, boundary conditions, and any solutions.
• beam.dbb—backup of the database file (binary).
• beam.err—error file (text). Listing of all error and warning messages.
• beam.out—output of all ANSYS operations (text). This is what normally scrolls in the output window during an ANSYS session.
• beam.log—logfile or listing of ANSYS commands (text). Listing of all equivalent ANSYS command line commands used during the current session.

Depending on the operations carried out, other files may have been written. These files may contain results, for example. It is important to know what to save—for instance, when there is a need to clean up a directory or to move things from the /scratch directory. If the GUI is always used, then only the .db file is required. This file stores the geometry, boundary conditions, and any solutions. Once the ANSYS programme has started, and the jobname has been specified, only the resume command has to be activated to proceed from where the model was last left off. If, however, ANSYS command files are intended to be used, then only the command file and/or the log file have to be stored. The log file contains a complete listing of the ANSYS commands used to get the model to its current stage. That file may be run as is, or edited and rerun as desired.

2.2.4 Printing and plotting

ANSYS produces lists and tables of many types of results that are normally displayed on the screen. However, it is often desirable to save the results to a file to be analysed later or included in a report.

In case of stresses, instead of using Plot Results to plot the stresses, choose List Results. Select Elem Table Data, and choose the appropriate item(s) from the menu. Multiple items can be picked. When the list appears on the screen in its own window, select File: Save As and give a file name to store the results. Any other solution can be done in the same way. For example, select Nodal Solution from the List Results menu to get displacements. Preprocessing and Solution data can be listed and saved from the List menu in the ANSYS Utility Menu. Save the resulting list in the same way described above.

When there is a need to quickly save an image of the entire screen or the current Graphics Window, from the ANSYS Utility Menu select Plot Ctrls → Hard Copy. There are two options: To Printer (see Fig. 2.5) and To File (see Fig. 2.6).

In the frame shown in Fig. 2.5, select the [A] printer from the list of printers and press the [B] Print button.

In the frame shown in Fig. 2.6, an example selection could be [A] Color, [B] BMP, [C] Reverse Video and finally [D] Save to. Then enter an appropriate file name and click the [E] OK button. This image file may now be printed on a PostScript printer or included in a document.

2.2.5 Exiting the programme

The ANSYS programme can be exited in a number of ways. When the current analysis is saved, from the Utility Menu select File → Exit. A frame shown in Fig. 2.7 appears.

There are four options, depending on what is important to be saved. If nothing is to be saved, then select [A] Quit - No Save as indicated.

The ANSYS programme has many finite element analysis capabilities, ranging from a simple linear static analysis to a complex nonlinear transient dynamic analysis. Building a finite element model requires more time than any other part of the analysis. First a jobname and analysis title have to be specified. Next, the PREP7 preprocessor is used to define the element types, element real constants, material properties, and model geometry. It is important to remember that ANSYS does not assume a system of units for intended analysis. Except in magnetic field analyses, any system of units can be used, as long as it is ensured that units are consistent for all input data. Units cannot be set directly from the GUI. In order to set units as the international system of units (SI), from the ANSYS Main Menu select Preprocessor → Material Props → Material Library → Select Units. Fig. 2.8 shows the resulting frame.

Activate the [A] SI (MKS) button to inform the ANSYS programme that this system of units is going to be used in the analysis.

2.3.1.1 Defining element types and real constants

The ANSYS element library contains more than 100 different element types. Each element type has a unique number and a prefix that identifies the element category. In order to define element types, the user must be in PREP7. From the ANSYS Main Menu, select Preprocessor → Element Type → Add/Edit/Delete. In response, the frame shown in Fig. 2.9 appears.

Click on the [A] Add button and a new frame, shown in Fig. 2.10, appears.

Select an appropriate element type for the analysis performed—for example, [A] Solid and [B] 8 node 183 as shown in Fig. 2.10.

Element real constants are properties that depend on the element type, such as cross-sectional properties of a beam element. As with element types, each set of real constants has a reference number, and the table of reference number versus the real constants set is called the real constant table. Not all element types require real constants, and different elements of the same type may have different real constant values. The ANSYS Main Menu command Preprocessor →Modelling → Create → Elements → Elem Attributes can be used to define an element real constant. Fig. 2.11 shows a frame in which one can select the element type. According to Fig. 2.11, the element type already selected is [A] Plane 183, for which the real constant is being defined. A corresponding [B] Material number, allocated by ANSYS when material properties are defined (see section below), is also shown in the frame.

Other element attributes can be defined as required by the type of analysis performed. Chapter 7 contains sample problems where elements attributes are defined in accordance with the requirements of the problem.

2.3.1.2 Defining material properties

Material properties are required for most element types. Depending on the application, material properties may be linear or nonlinear, isotropic, orthotropic or anisotropic, constant temperature or temperature-dependent. As with element types and real constants, each set of material properties has a material reference number. The table of material reference numbers versus material property sets is called the material table. In one analysis there may be multiple material property sets corresponding with multiple materials used in the model. Each set is identified using a unique reference number. Although material properties can be defined separately for each finite element analysis, the ANSYS programme enables storing a material property set in an archival material library file, then retrieving the set and reusing it in multiple analyses. Each material property set has its own library file. The material library files also enable several users to share commonly used material property data.

In order to create an archival material library file, the following steps should be followed:

1. 1. Tell the ANSYS programme what system of units is going to be used.
2. 2. Define the properties of, for example, isotropic material; use the ANSYS Main Menu and select Preprocessor → Material Props → Material Models. A frame, shown in Fig. 2.12, appears.

As shown in Fig. 2.12, [A] Isotropic was chosen. Clicking twice on this calls up another frame, as shown in Fig. 2.13.

Enter data characterising the material to be used in the analysis into the appropriate field: for example, [A] EX = 2.1e9 and [B] PRXY = 0.33, as shown in Fig. 2.13. If the problem requires a number of different materials to be used, then the above procedure should be repeated and another material model is created with appropriate material number allocated by the programme.