Ansys User Guide

University of Sheffield Department of Mechanical Engineering

Dr A Yoxall Department of Mechanical Engineering 1

ANSYS USER GUIDE 1

ANSYS USER INTERFACE 3

ANSYS MENU STRUCTURE 8

ANSYS FILE TYPES 13

ENTITY SELECTION METHODS 16

ANSYS MODEL VIEWING AND HARDCOPY 19

MODELLING IN ANSYS 22

ANSYS TUTORIAL MECH 209 35

Dr A Yoxall Department of Mechanical Engineering 2

Ansys User Interface

Ansys is a good pre-processing, solution and post-processing tool for finite element modelling. The Ansys program is organised into two levels. The initial entry level is the BEGIN level. From this level you can access the desired processors as shown below.

Enter Ansys Exit Ansys

OTHER POST26

Processor Level

POST1SOLUPREP7

BEGIN LEVEL

The Ansys graphical user interface (GUI) is split into four main areas. the graphics area, the utility menu, the main menu and the Ansys toolbar.

Highlighted in the figure below is the standard layout of the GUI. The different windows that make-up the GUI can be moved around the screen at the users discretion.

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The Graphics Area

The Graphics area is the window in which the entities are displayed. The window can be split into smaller windows. Within these windows entities can be animated, rotated, selected, deleted and so on.

The Utility Menu

The Utility menu is the light blue menu shown below

This menu contains controls for opening and saving files, selecting entities, producing plots etc. By clicking on any of the 10 options pop-up menus under each option appear.

The ten options are:

File File opening, clearing a database, saving, importing and exporting files

Select Selecting entities and components

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List Lists entities and components

Plot Plots entities and components, multiple plots, array parameters

and material data

PlotControls Hardcopy, component numbering, annotation, animation and plot style

WorkPlane Working plane creation and manipulation, coordinate system

creation and manipulation

Parameters Array parameters, scaler parameters and parameter edit

Macros Macro creation for data manipulation

MenuCtrls Controls the format of the GUI

Help Online help and documentation

The Ansys Input

This window shows program prompt messages and allows you to type in commands. All previously typed commands also appear in this window.

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The Ansys Toolbar The Ansys toolbar menu has options for saving and resuming models, powergraphics and web-interfacing.

The Main Menu

The main menu consists of nine options. Each menu topic brings up a submenu (indicated by a > after the topic) or performs an action. The symbol on the right-hand of the topic indicates the action.

These are.

Preferences This sets model preferences, such as thermal, structural or modal analysis

Preprocessor Enters the preprocessing sub-menu

Solution Enters the solution sub-menu

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General Postproc Enters the general postprocessor

TimeHist Postproc Enters the time history postprocessor

Design Opt Enters the Design Optimisation routines

Radiation Matrix Sets options for radiation thermal analysis

Run-Time Stats Gives run-time statistics

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Ansys Menu Structure From each of the menu bars, further menus appear. These menus can lead to further pop-up menus, sub-menus, data entry fields and toggles.

All menus are similar to the main menu in colour and in operation. Each menu acts like a tree to further menus all of which stay displayed until unselected.

Sub-menus

From the main menu a sub-menu will look like the one shown below.

The preprocessor menu is extremely important. Most of the work in creating a model is done from this menu.

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From the utility menu a sub-menu will look like the one shown below.

Pop-up Menu

A pop-up menu will typically look like the one shown below. Note that the menu is split into several areas.

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At the top of the menu is the pick or un-pick option. With this we can either select or un-select entities using the mouse buttons. The next field tells us the location of the item and number of items we are picking. Below this area is the data entry area. At the bottom of the pop-up menu is a set of buttons for applying the required command. These buttons are common to Ansys pop-up windows and function as follows:

OK This applies the command and closes the window

Apply This applies the command and leaves the window open

Reset Resets the picked or un-picked options

Cancel Cancels the command and closes the window

Help Produces online help

Data Entry Field

A data entry field will typically look like the one shown below.

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Data such as Young’s Modulus and Poisson’s ratio can be entered using the keyboard in the required field.

Toggle

Toggle boxes allow certain options to be set without actually typing anything. They are typically used when Ansys want the user to choose between one option and another.

In the toggle box shown above we are choosing to import a CAD file using the default option and also choosing to combine (merge) coincident keypoints thus enabling us to create a areas and volumes.

Exiting Ansys

We can leave Ansys by clicking on file from the utility menu and then exit at the bottom of the following menu.

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This action brings up the following toggle menu.

This menu gives the user four options for saving and exiting the model.

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Ansys File Types

As can be expected with a powerful Finite Element tool such as Ansys various different files are created during the different phases of model creation. Most files can be created from the file sub-menu from under the utility menu.

Importing Files Files can be imported from different CAD programs. Using the File option from the utility menu.

Brings up the sub-menu.

By clicking on Import a further sub-menu gives us our file options. Typically this might be an IGES file. Finally a toggle-box will appear offering several options.

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In version 5.4 of Ansys (our current version) objects imported by the Default option cannot be altered. If further work is required to the object then the Alternate option is necessary. Ansys will try and create volumes and areas from the lines imported from the CAD geometry.

Saving Files You can save files in Ansys using the File sub-menu as described earlier. The file will automatically save as file.db (the default jobname). This is known as the database. A back-up of your database has the file extension dbb. The original database is always copied to a dbb file when a save command is executed.

To read a database into Ansys use the resume command from File sub-menu.

Exporting Files

IGES files can be exported from the File sub-menu using the export option.

Solution Files During an analysis Ansys creates various files for storing data. These are.

File.emat element matrix file on previous iteration

File.esav element matrix file on most recent iteration

File.tri triangularised matrix files

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File.err file listing all error messages generated during modelling

File.log log file of all commands issued

File.page scratch file for virtual space

The esav, emat and tri files are automatically deleted after leaving Ansys once a job has been solved. This feature is unique to Sheffield University. There are several other files created for different applications, which will not be dealt with in these notes.

Results Files

For a standard structural analysis the results file has the extension .rst. Hence a default result file is file.rst

All Ansys files can be copied renamed and saved in the appropriate operating system.

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Entity Selection Methods

Ansys has an extremely powerful select logic. This select logic is available from the File utility menu under select. It is tremendously useful to understand how this works.

The select sub-menu is shown below.

Entities that you can select are nodes, elements, keypoints lines, areas and volumes. The default option is nodes.

The sub-menu is divided into three areas. The top portion allows us to toggle onto which entities that we wish to select. The second toggle box in this portion allows us to choose how we would like to select the entities. There are many different ways in which we can do this. Several examples are shown in the following sub-menus.

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Using this sub-menu we can select lines by their global position in the current co-ordinate system. A very useful technique is to be able to select things attached to entities we have already selected. So for instance we can select lines attached to areas, keypoints attached lines and so on. In the sub-menu shown we are selecting areas attached to the lines that we have already selected.

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The second portion of the sub-menu offers four options on what we select our entities from. These four are.

From Full select entities from all entities that exist

Reselect select entities from those already selected

Also Sele add to the entities already selected

Unselect unselect entities already selected

Also in this portion of the sub-menu are buttons so that we can select everything, invert our current selection and select none of the entities chosen.

The bottom portion of the panel is our standard Ansys area for executing our desired commands.

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Ansys Model Viewing and Hardcopy

The ANSYS program allows you to pan, zoom and rotate your model. There is a special sub-menu from the utility menu for doing this under Plot Controls.

Note that this sub-menu has options for various graphics options. Through this menu we can change the style of our graphics plot, the colours used, the number of windows and so on. From this window we are also able to produce hardcopy. Clicking on hardcopy will bring up the following sub-menu. By choosing graphics window only, color and print file, the graphics window output will be printed on a colour print. You must make sure that the print option is set to lpr –Pstgcolps for the output to be produced at StGeorge’s IT centre. Note that the file is automatically saved as an encapsulated postscript file. Note that only postscript can be printed directly to the StGeorge’s printers.

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After clicking on pan, zoom rotate the following sub-menu appears.

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This menu is extremely useful for manipulating the model within the graphics window. The top portion of the menu contains button for selecting standard user views such as isometric or oblique. Below these standard view are options for zooming in or out of portions of the model. The next portion of the menu translates or rotates the model. The bottom portion of the menu allows dynamic manipulation of the model.

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Modelling in Ansys

There are five main phases of the Ansys modelling process.

Geometry creation and editing

Element creation and editing

Load and boundary condition application

Solving of analysis

Results scrutiny and post-processing.

The main menu bar allows access to the functionality needed for these tasks.

Introduction to some sub-menus

The pre-processor sub-menu is shown below. From only a small number of sub-menus below this, a model can be created, meshed and loaded.

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Element Type this sets the element type that we are going to use during our analysis.

Real Constant real constants are element dependant properties.

Material Properties this sets the material properties such as Young’s

Modulus and Poisson’s ratio

You must always choose an element type and material property before attempting to run any analysis in Ansys.

Note that the pre-processing menu is split into several sections, modelling, attributes meshtool and so on. The modelling section allows us to create the required geometry the first phase of our modelling process.

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Using the create sub-menu we can produced our geometry from pre-defined shapes called primitives. These shapes can be circles, rectangles, blocks and several other shapes outlined in the menu.

The create rectangle sub-menu offers several options for producing a rectangle and is shown below.

If we use the by-dimensions option then the following data entry box appears.

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We can put the dimensions of the rectangle we desire into the boxes and a rectangle will appear in the graphics area.

In Ansys surfaces (areas) are made up of lines. Lines are connected together by keypoints. A plot of the lines forming a rectangle is shown in the following figure.

We can similarly create three-dimensional shapes using the same process. In Ansys these three-dimensional shapes are known as volumes.

A volume is shown below.

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A volume is made from a set of areas.

Meshing

The second phase of our modelling process is the element creation. From the pre-processor menu we can see that one of the sub-sections is labelled Meshing. By clicking on mesh, the following sub-menu appears.

This menu allows us to free or map mesh areas or volumes. Free meshing means the surface will be meshed with quadrilateral and triangular elements. Mapped meshing means the surface will be only meshed with quadrilateral elements. Only certain geometry’s can be map meshed.

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Within the Meshing area of the pre-processor menu are options for element size control and other meshing functions. In Ansys all these option are combined in a sub-menu called the Meshtool. This menu is shown below.

From this menu element size can be set, the mesh can be refined and so on. Loading and boundary conditions We can apply loads and constraints (and delete them) either from the preprocessor or the solution processor sub-menus.

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If we click on apply the following sub-menu appears.

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If we choose Force/moment the following sub-menu appears.

We can apply forces on nodes or keypoints. Choosing nodes our standard pop-up menu appears. After picking the nodes on which we want to apply the force, the following data entry box appears.

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By toggling on the Direction of force/mom button we can choose the loading direction of the force. We will then be prompted with our standard pop-up menu. The force will be represented as a red arrow. Similarly by clicking on apply then Displacement from the solution processor window then following sub-menu appears.

By clicking on nodes our standard pop-menu will appear

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After picking the nodes we wish to constrain the following data entry box appears.

Highlighting ALL DOF and making the value of the displacement zero fully constrains the selected nodes. Blue arrows represent tranlational degrees of freedom and brown arrows rotational degrees of freedom. Solving of analysis We enter the solution processor from the main menu as shown below.

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We can also apply loads and constraints from the solution processor. To solve an analysis we click on solve current ls. Results scrutiny and postprocessing After clicking on the main menu General Postprocessor the following sub-menu appears.

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If we then click on Nodal solution the following sub-menu appears. Note that we are able to select our desired output firstly by highlighting the item (stress, strain etc) and then the component (sx, sy etc).

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Once we have decided on our output by clicking OK (or apply depending on preference) we should get output as shown below.

The default stress output is for the mid surface of the shell element. To select the top or bottom surface, type top or bottom in the input menu before plotting the stress.

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Ansys Tutorial Mech 315

Creating the Geometry

In this tutorial we create a bracket using the dimensions defined by each users individual problem. The tutorial should be used in conjunction with the Modelling in Ansys guide. The general dimensions of the bracket are shown below.

1000 mm

300 mm 100 mm

Applied loads on this edge

Applied loads on this edge

Centre Line

Offset

Before starting to create the geometry don’t forget to set the element type, real constant and material property. The element type we are going to use is SHELL63. This is a four noded elastic shell element. Remember that real constants are element dependent properties. For SHELL63 elements the real constant applies thickness to the element.

We can choose this information from the preprocessor menu. Clicking on element type brings up the following sub-menu.

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In this menu by clicking on add we can define our elements types. Note that in the window above one element type has already been defined. By clicking on add a following element library menu appears.

The element library menu contains all the Ansys element types. Highlighting the required type and clicking on OK will define a particular type.

Once element types have been defined, element dependent properties or real constants must also be defined. Again from our preprocessor menu, clicking on Real Constants brings up the following menu.

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By clicking on the add button we can define real constants for our particular element type. The next menu prompts us for what element type we wish to attach the real constant to.

In this tutorial the element type we want to attach the real constant to is SHELL63.

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By clicking on OK, the data entry menu for SHELL63 appears.

In this tutorial we only need to entry the Shell thickness at node I. After you have defined the real constant click on OK.

If you have problems finding the close button on the Real Constants menu stretch the menu downwards and click on close.

Material properties are also defined from the preprocessor menu. Note that the material we wish to define is isotropic. The material property is defined using the data entry menu shown in the Ansys user interface guide.

There are several ways in which we can tackle a problem like this in Ansys. One way is to create our plate from rectangular areas, create an area for the ‘hole’ and then subtract our ‘hole’ from the plate.

The plate should be split into three sections. Each section should be the same length and height. The reason for doing this is so that there will be node points at the correct positions where we would like to put the load

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We create our rectangular areas by clicking on create Rectangle option on the preprecossor sub-menu create.

This brings up the following sub-menu giving us options for how we create our rectangle.

By clicking on the By Dimensions option the following data entry box appears.

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From this we can put the size of the rectangle we wish to create. By repeating this operation we can produce the geometry of the plate.

Instead of creating lots of rectangles we could use the preprocessor copy or reflect commands. The logic of how to copy entities is explained next.

Once we have created our first rectangle geometry, we can copy the areas, lines and keypoints to create the three rectangles forming the plate. Using the preprocessing menu and the clicking on copy brings up the following sub-menu.

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By clicking on areas our standard pop-up menu appears.

Once you have selected your areas click on apply (or OK depending on your preference). The following data entry box should appear.

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Note that the ITIME entry field defaults to the number two. This is the minimum number to create one copy. The ITIME number includes the original pattern set when deciding on how many copies are to be generated.

To combine (merge) keypoints type nummrg,kpoi,0.01,0.01 in the Ansys input menu. This combines coincident keypoints so that nodal connectivity is maintained in the model.

Once we have created our plate the next step is to create the ‘hole’. If we use the primitives option for creating the hole then we must move the working plane to our hole centre. The working plane is a co-ordinate system that can be moved to any position in space. Primitives are always built on the x-y plane with z as the vertical axis. So by moving the working plane to the ‘hole’ centre we can create a rectangle that has it’s centre orientated at the centre of the plate. To move the working plane, click on Working Plane from the Utility menu. The following sub-menu appears.

By clicking on Offset WP by Increments the following sub-menu appears. From this menu we can move the working plane either by translating the plane or by rotating the plane through a certain angle. In this tutorial we will only translate the working plane to the centre of the hole. Type the x and y offsets required in the X,Y,Z Offsets field.

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Note that a comma separates each offset dimension. In Ansys commas separate all input fields.

Click on OK to close the sub-menu.

Again, using the preprocessor create sub-menu, by clicking on create area rectangle and by dimensions we can create our rectangle (making up the hole) as we did earlier. Note that the ‘hole’ rectangle dimensions are defined by the users individual problem

Select the ‘hole’ area and click on OK. Plot the lines. You might get a yellow warning box like the one shown below when you try and select this area.

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And the ‘wrong’ area highlighted as shown below.

We can use the OK, Prev or Next buttons to toggle between the selections as shown below.

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Once we have selected our correct area we click on OK on the yellow box and OK on the pop-up menu.

Using Ansys select logic, select the lines that are attached to that area. Plot the lines. You should see a set of lines forming your rectangular area. From the preprocessor menu, click on delete and then areas. Do not click on areas and below as this will delete the area, the associated lines and keypoints. You will be prompted with the following pop-up menu.

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Now we will create the fillets between the lines. From the preprocessor sub-menu create click on line fillets. Using the pop-up menu click on the lines you wish to create the fillet between (two lines maximum). After clicking on apply the following menu appears. Using this menu we can set the size of the radius.

By clicking on apply we can create all the necessary fillets.

Eventually we should create an object that looks like the one shown in the figure below.

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No we need to re-create the area. Using the preprocessor create area sub-menu and by clicking on by lines, we get the following pop-up menu.

Click on the lines in-turn and click-on OK. Ansys cannot create the area unless the lines are connected. If this is a problem, use the nummrg command outlined earlier.

Once we have created the area, select all the entities using the Utility menu. We are now going to use boolean operations the preprocessor operate menu. Boolean

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operations are immensely powerful tools. They allow us to add, subtract, divide and glue entities together. By this method we can easily create complex geometry.

Click on operate from the preprocessor sub-menu. Using the add option add the three original areas together. You will be prompted with a pop-up menu asking you what areas you want to add.

Once you have done this click on the subtract option and subtract the ‘hole’ from the areas you have just added together. You may get the yellow warning box again whilst doing this operation. Toggle between the options as described earlier. When you try and subtract the area you will be first prompted with a pop-up menu asking you which area do you want to subtract from (the base area). Click on the larger area and then apply. You will then be prompted for which area you want to subtract. Click on the ‘hole’ area and OK.

Eventually if you plot the lines you should get something similar to that shown below.

Meshing the Geometry

We must now mesh the geometry. Using the preprocessor mesh option the following sub-menu appears.

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We wish to free mesh our areas so by clicking on Free the following sub-menu appears.

We can then pick the area and then click on OK.

Using the utility menu plot function we can plot any entity that is selected. If we plot (or replot) the elements our finished structure should look like the one shown below.

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The model should not contain more than 1500 elements. A model larger than this will not run in your account. Loading and boundary conditions

Loads and constraints can be applied as described in the Modelling in Ansys tutorial. The loads should be applied at nodes on the right-hand edge of the plate. The nodes are 100 mm apart and equidistant around the centre line of the plate. The loading condition is 250 N at each node and perpendicular to the plane of the plate.

P

P100 mm

Loads, P are equal to 250 N

10 mm

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Constraints (boundary conditions) must be applied to the nodes at the left-hand edge of the plate. The plate is to be fully constrained at this point. Use Ansys select logic to select the nodes. Again, use the Modelling in Ansys tutorial to apply the constraints. Once the constraints have been applied make sure you select everything before proceeding further.

Solving of analysis

The analysis can be solved from the solution processor using solve current ls option in the solution processor.

Results scrutiny and postprocessing

In analysing the structural integrity of this bracket we need to know the maximum principal stress and the minimum principal stress on the plate and the Von Mises stress.

Select the element surface you wish to look at by typing top or bottom before plotting the stresses in the plate.