Tutorial for ANSYS®

Release 6.1 Finite Element Analysis Software

For Unix Based Workstations

Truss, Frame, and Plate Examples By Andrew R. Mondi Using examples and revisions from: Cosmos-GeoStar Tutorial, January 2000, by Keith M. Mueller Department of General Engineering at the University of Illinois at Urbana-Champaign May 2003 Corrections: May 18, 2004

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ACKNOWLEDGMENTS This tutorial is based upon Cosmos-Geostar Tutorial written by Dr. Keith M. Mueller in January 2000. The example problems solved in that tutorial are also solved here. I tried to incorporate the strengths of Cosmos-GeoStar Tutorial into this ANSYS tutorial, even though the structure and content of each are quite different. I thank Professor David E. Goldberg for his guidance while writing this booklet. He is a skilled manager and leader. I thank Mr. Raja R. Katta for his assistance. His concise and timely explanations of difficult material in ANSYS were essential for swiftly completing this project. Also, I thank Professor Thomas F. Conry for his advice and suggestions for refining and improving this tutorial.

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TABLE OF CONTENTS 1. INTRODUCTION What is ANSYS? 1-1 Helpful Web Links 1-1 Purpose of this Tutorial 1-1 Using this Tutorial Effectively 1-1 Starting up in a Unix System 1-2 Default View in ANSYS 1-3 Familiarizing Yourself with ANSYS 1-3 2. TRUSS EXAMPLE 2-1 Preprocessing 2-1 Introduction 2-1 Modeling 2-2 Element Type 2-7 Real Constants 2-8 Material Properties 2-10 Meshing 2-12 Solution Phase 2-16 Analysis Type 2-16 Apply Constraints 2-16 Apply Loads 2-17 Apply Solution 2-19 Post-processing 2-20 Reaction Forces 2-20 Member Forces and Axial Stresses 2-20 Displacements 2-23 3. FRAME EXAMPLE 3-1 Preprocessing 3-1 Introduction 3-1 Modeling 3-1 Element Type 3-2 Real Constants 3-2 Material Properties 3-4 Define Sections 3-4 Meshing 3-5 Solution Phase 3-7 Introduction 3-7 Analysis Type 3-7 Define Frame Constraints 3-7 Define Frame Loads 3-7 Apply Solution 3-9

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3. FRAME EXAMPLE (continued) Post-processing 3-9 Introduction 3-9 Reaction Forces 3-10 Member Forces and Stresses 3-10 Member Displacements and Rotations 3-10 4. PLATE EXAMPLE 4-1 Preprocessing 4-1 Introduction 4-1 Modeling 4-2 Element Type 4-4 Real Constants 4-5 Material Properties 4-6 Meshing (and refining a mesh) 4-6 Solution Phase 4-8 Introduction 4-8 Analysis Type 4-8 Apply Constraints 4-8 Apply Loads 4-9 Apply Solution 4-10 Post-processing 4-10 5. APPENDIX 5-1 Working with ANSYS in Unix 5-1 Saving an ANSYS file 5-1 Opening a previously saved ANSYS file 5-1 Printing result tables 5-2 Printing graphical output 5-2 Managing your EWS Account 5-2 How to Access EWS files 5-2 Deleting EWS files in Unix 5-2 Creating Axisymmetric Models 5-3 General Notes on Understanding ANSYS 5-5

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1. INTRODUCTION What is ANSYS? ANSYS is a finite element analysis (FEA) software package. It uses a preprocessor software engine to create geometry. Then it uses a solution routine to apply loads to the meshed geometry. Finally it outputs desired results in post-processing. Finite element analysis was first developed by the airplane industry to predict the behavior of metals when formed for wings. Now FEA is used throughout almost all engineering design including mechanical systems and civil engineering structures. ANSYS is used throughout industry in many engineering disciplines. This software package was even used by the engineers that investigated the World Trade Center collapse in 2001. More information about the ANSYS FEA package and other ANSYS products can be found at <www.ansys.com>. Helpful Web Links Another ANSYS tutorial produced by the University of Alberta, Canada can be accessed at <http://www.mece.ualberta.ca/tutorials/ansys/>. Links and design tips can be accessed at <http://www3.hsympatico.ca/peter_budgell/home.html>. Some commentary on the mathematics behind FEA software by the National Institute of Standards and Technology can be accessed at <http://math.nist.gov/mcsd/savg/tutorial/ansys/FEM/index.htm>. Purpose of this Tutorial The purpose of this tutorial is to guide students in the Department of General Engineering at the University of Illinois at Urbana-Champaign through their structures courses (GE 221 and GE 232). It is designed to familiarize the user with the basic functions of ANSYS FEA software. Examples of a simple truss, a frame (using beam members), and a two-dimensional plate are explored. Using this Tutorial Effectively This tutorial is designed so that the reader completes each example in the order it is presented. The latter tutorials (frame and plate) assume the user understands certain functions of the program covered in earlier examples. First a truss is analyzed. This is the simplest of the three models investigated in this tutorial. This is also the longest of the three tutorials because it is the most detailed of the three examples and it does not assume any prior knowledge of the user. Next a frame is explored. Here the user defines sections and outputs internal member moments and member rotations. Once completing this tutorial, the user should be able to apply its principles to all types of two dimensional beam problems. Finally a two dimensional plate is analyzed. This example is useful for those users investigating stress concentrations and other solid mechanics properties.

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Starting up in a Unix System After logging onto the workstation, you will see an x-term window (Figure 1-1) on the desktop:

Figure 1-1 x-term window At the prompt in this window, type ansys, which creates a new window (Figure 1-2) on the desktop titled “Tansys” with square icons. Click the top icon, ANSYS NOW. Note: the question-mark icon accesses Help.

Figure 1-2 Tansys window First, a session file screen (Figure 1-3) will pop-up. You should not perform any operations in this window. You may need to wait for a few seconds until the graphical-interface component of the program launches and you see the graphical interface (Figure 1-4 on the next page):

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Figure 1-3 Session file window

Figure 1-4 ANSYS with graphical interface

Default View in ANSYS The default view in ANSYS is well suited for two-dimensional designs with the x-axis pointing horizontally to the right, y-axis pointing vertically upwards, and the z-axis pointing out of the screen. Zoom and repaint (or refresh screen) commands are very similar to those used in most CAD or word processing software.

Familiarizing Yourself with ANSYS The fastest, easiest and most logical way to use ANSYS is through the Main Menu located on the far left-hand side of the screen (Figure 1-5 at left). It may look intimidating at first glance however think about the information that you need to solve for all of the components in a structure. You need to know the position, length, and material of the structural members, the position, magnitude and direction of all the loads on the structure, and the constraints on the structure. In order to get ANSYS to work properly, you simply need to tell the program this information and it will do the rest for you!

Figure 1-5 Main Menu

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The Main Menu is designed so that you complete the steps required to build your model by beginning at the top of the menu and working your way down. For the purposes of this tutorial, you will need to be familiar with three of the commands on the Main Menu: Preprocessor, Solution, and Post-processor (noted as General Postproc on the ANSYS main menu) – as you can see in Fig. 1-5, these are the first three commands on the Main Menu. The construction steps to be accomplished in each command are listed below: Preprocessor Solution Post-processor 1. Member length 1. Load position Get displacement member 2. Member position 2. Load magnitude force data in both graphical 3. Member material 3. Load direction and text output. You will use this Main Menu just like Windows Explorer or any other function that is organized in a “tree fashion”. You should complete these three major steps: (1) Preprocessing stage, (2) Solution, and (3) Post-processing stage IN THE ORDER GIVEN. If you do not, ANSYS will not know how to properly solve your structure and give you bad results. The rest of this tutorial will bring you through three helpful examples that will familiarize you with ANSYS. Also information concerning printing, managing your EWS account and other helpful Unix tips is in the Appendix at the end of this tutorial.

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2. TRUSS EXAMPLE Given the following loaded truss, find the internal forces in all members and displacements of all joints.

Figure 2-1 Given truss For illustrative purposes, the four diagonal members will be assumed to be aluminum and have an area of 30 in2, and the three horizontal members will be assumed to be steel and have an area of 10 in2. While this creates a somewhat unrealistic truss, it will allow for demonstration of modeling a truss containing different materials and member sizes. Remember: Think about the modeling processing as having 3 major steps: Preprocessing, Solution, and Post-processing. ANSYS is constructed in an outline format. In each of these major steps, there are small sub-steps. This tutorial is built so as to mimic this outline structure. Always be thinking about where you are in the modeling process and how the steps you are completing are meaningful and can be used in other problems you will solve in your classes. I. Preprocessing

A. Introduction – several steps will be completed in the Pre Processing stage: 1. Modeling (define Keypoints and lines and using plot controls) 2. Element Type (2D truss spars) 3. Real Constants (define cross-sectional areas of truss spars) 4. Meshing (one division per element)

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B. Modeling 1. Keypoints - The first step in

designing any structure in ANSYS is to define the Keypoints of the structure. These points simulate the joints of the structural members and also serve as endpoints of the members. a. On the Main Menu, left click

the plus sign next to Preprocessor. A sub-menu will drop-down listing all of the commands you can use in the Preprocessing stage.

b. Left click the small plus sign next to Modeling. Another sub-menu of all modeling commands is listed here.

c. Left click the small plus sign next to Create. This menu lists all of the objects you can create in ANSYS. You will be creating points and lines.

d. Left click the small plus sign next to Keypoints. Click the small icon next to Active CS. The pop-up window will prompt you for a keypoint number and a set of

coordinates for that keypoint.

Figure 2-2 Main Menu

Note: This sequence of steps will be summarized using the following notation: Preprocessor>Modeling>Create>Keypoints>Active CS

The Create Keypoints window will appear:

Figure 2-3 Create Keypoints window

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e. At this juncture you should choose how to define all of the Keypoints in

your structure. Remember that Keypoints represent joints of your structure’s geometry so number ALL of the joints in your design. It is often best to number the joints in a logical manner that you can remember easily. For this example the joints have been defined below:

Figure 2-4 Given truss with numbered keypoints (joints)

f. The Create Keypoints window (Figure 2-3) tells ANSYS where your keypoints (or joints) are located. In the Keypoint number box enter a 1. In the X, Y, and Z coordinate boxes place a 0.

g. Select Apply. Sometimes the entries in the box will clear, other times they will not clear away and you must overwrite them. ANSYS is now ready to accept the coordinates for another point.

Note: ANSYS does not work in any pre-defined unit system – it is your responsibility to be consistent with your units (i.e. do not enter your lengths in feet and loads in Newtons!). For this example, we will use inches for length and pounds for load. This way we will be certain that our stresses will be in units of psi.

h. Define point 2 just as you did for point 1: enter 2 into the keypoint number box at the top and 200 in the x box, 200 in the y and 0 in the z box.

Helpful Hint: If you do not enter a point value, ANSYS will assign a zero for that coordinate component. Thus, for two-dimensional models, you may always leave the z-coordinate box blank.

i. Define points 3 and 4 as above. Once you have entered all of the information for the final keypoint (point 5), click the “OK” button. This will create the point and close the dialog box.

Note: If you select “Apply” on the last point you need to enter, DO NOT SELECT “OK”. Instead choose “Cancel”. As mentioned earlier, ANSYS takes default coordinates as

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zero; if you press “OK”, ANSYS will define a new point at (0,0,0)! Note: If you need to remove keypoints that you have already created, go to Preprocessor>Modeling>Delete. You will find that there are Delete commands that correspond to all Create commands. Now all of the points for our truss have been defined.

Figure 2-5 All keypoints defined

2. Lines (Defining Members) - In ANSYS, lines represent structural members. You define lines by connecting the keypoints created previously.

a. Begin by numbering your structure’s members on your paper copy for

your own records. This is done for you below:

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Figure 2-6 Given truss with numbered members

b. Go to Preprocessor>Modeling>Create>Lines> Lines> Straight Line in the Main Menu. The Create Straight Line window will appear (at right).

c. Be sure that the options Pick, Single, and List of Items are selected. Move your mouse cursor to a Keypoint that will serve as the start of the first member you wish to define; we will begin with member 1. Your mouse cursor will appear to be a small vertical arrow pointing upwards. Left click once on point 1 (0, 0). A yellow box will highlight this point.

d. Move the cursor right to point 2 (200, 200). Left click once near or on point 2. This defines the member 1. ANSYS will provide a preview sketch of member 1.

Figure 2-7 Create Straight Line window

Figure 2-8 Line (member) 1 defined

Note: The process is the same for defining all other members: left click once on the start point, move to the end point and left click once.

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e. Define the other six members of the truss in the order they were assigned. Once all of the lines (members) have been defined, your model should look like the one below.

Figure 2-9 All members defined Note: The lines (members) are denoted by L1, L2 etc. Your keypoints (joints) are denoted simply by numbers. Remember, there may be a difference in numbering between KEYPOINTS and NODES (this will be discussed in greater detail later).

3. Using Plot Controls - now that you have finished plotting lines, you should familiarize yourself with helpful viewing options in ANSYS. a. Go to the Plot menu on the menu bar at the top of your screen.

Figure 2-10 Plot command on the menu bar b. Select the first command on the drop-down menu, Replot. See that the

lines and perhaps your keypoints have disappeared. In order to see your model, you must change the plot controls.

c. In the Plot drop-down menu select Lines. Now you should be able to see your model.

d. Go to the PlotCtrls menu (to the right of the Plot menu) and select Numbering. The Plot Numbering Controls window will pop-up.

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Figure 2-11 Numbering window

e. Turn on the Keypoint and Line numbers options and select OK. Now you should be able to see your truss completely numbered.

Note: Throughout this tutorial you may need to Replot your model several times to get a good visual representation of your model. Know that you can turn on and off visual components of your model using the options under the Plot and Plot Controls (PlotCtrls) command on the top menu bar.

C. Element Type 1. Go to Preprocessor>Element Type>Add/Edit/Delete in the Main Menu. The

Element Type window will pop-up.

Figure 2-12 Element Type window

2. Select “Add...” The Element Type Library window will pop-up.

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Figure 2-13 Element Type Library window

3. In this window set the following: a. Select “Link” in the left hand box. This means that this element will be a

truss link. b. Select “2D spar” in the right hand box. This will force your truss members

to be displaced in 2 dimensions. c. Leave the default 1 for element reference type number. d. Select OK, this will close the Library window. e. You will return to the Element Types window (Figure 2-12). Click close.

D. Real Constants - next you must define the cross-sectional areas for the members

of your truss. 1. Go to Preprocessor>Real Constants>Add/Edit/Delete in the Main Menu. The

Real Constants window will pop-up.

Figure 2-14 Real Constants window

2. Select Add... so that the Element Type for Real Constants window will pop-up.

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Figure 2-15 Element Type for Real Constants window

3. Note that "Type 1 - LINK1" is already highlighted. Select OK. The Set Constants window will pop-up. Note that you are in Real Constant Set Number 1.

Figure 2-16 Set Constants window

4. Enter the following in the Set Constants window: a. Enter the cross-sectional area for Al (30) [in units of in2]. b. Initial Strain is 0. c. Click Apply. This will store the information for aluminum. ANSYS is

now prepared to receive the set of real constants for steel (type 2). d. Set Real Constant Set No. to 2 e. Enter the cross-sectional area for steel (10) [in units of in2]. f. Initial strain to 0

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Figure 2-17 Set Constants window with those for steel

g. Click OK. The box will close and you will return to the Real Constants window.

h. Click Close in the Real Constants window. Now there are two real constant sets for cross-sectional area defined (one for each material).

E. Material Properties - now you must define the materials that make up your truss

members. Remember that the diagonal members are aluminum and the horizontal members are steel. 1. Go to Preprocessor> Material Props>Material Models. The Material Behavior

window will appear. This window is divided into two regions: Material Models Defined on the left and Material Models Available on the right. Note that “Material 1” has already been created - ANSYS is waiting for you to define it.

Figure 2-18 Material Model Behavior window

2. In this window, left click on Material 1 so it is highlighted (this may already be done).

3. On the right hand side double click on Structural>Linear>Elastic> Isotropic. This will launch a new pop-up window Material Properties for Material Number 1.

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Figure 2-19 Material Properties for Material Number 1

4. The box EX is for the Elastic Modulus of the material. PRXY is for Poisson's Ratio. For all two-dimensional models (spars), Poisson's ratio is not used, so it doesn’t have to be entered, but it is a good idea to be in the habit of entering it. For this example, let us make Material 1 behave like aluminum with an Elastic Modulus of 10,000,000 psi (10,000 ksi). a. Enter 10000000 in the EX box b. Enter 0.3 in the PRXY box c. Select OK. You will return to the Define Material Behavior window. d. Select the Material drop-down menu in the upper left-hand corner of the

window and select New Model. A pop-up window asking for a Material ID number, click OK (the default number is sufficient).

Figure 2-20 Material Menu location in Define Material Behavior window

Figure 2-21 Material ID window

5. In the Material Model Behavior window (Figure 2-18) click on Material 2 in the left hand box so that it is highlighted.

Note: we will follow the same steps to define Material 2 (steel) as we did for Material 1 (aluminum).

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6. In the right hand box and double click on Structural>Linear>Elastic> Isotropic (this may already be done). The properties window for Material Properties for Material Number 2 will pop-up (Figure 2-19).

7. Define the elastic modulus (EX) to be that of steel for this example (30000000 psi) and Poisson's ratio (PRXY) to be 0.3.

8. Select OK and exit out of this window by clicking on the close box or selecting Exit in the Material Menu.

F. Meshing - the Mesh function is the heart of ANSYS! Meshing is like breaking

your structure into small pieces that ANSYS can recognize and then “gluing” these pieces of your model together. Once this is complete, it is difficult to pull it apart so you should save your model NOW (see Appendix, page 5-1, if you do not already know how to do this). 1. Go to Preprocessor>Meshing>Mesh Attributes>Picked Lines. The Pick Line

Attributes window will pop-up. Be sure that Pick and Single are selected.

Figure 2-22 Pick Line Attributes

2. In the workspace, note that the mouse will be a small black upward pointing arrow.

3. Select lines 1, 3, 5 and 7 (all the diagonals), each with a single left click. Note: You may want to turn line numbering under PlotCtrls>Numbering to see the line numbers if this is not already done.

4. Select OK in the Line Attributes window. The Define Line Attributes window will pop-up.

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Figure 2-23 Define Line Attributes window for material 1 (aluminum)

5. In this window you can set the Material Number, Real constant number and Element type for the lines that you selected. Since you selected all of the aluminum members, define these lines accordingly: a. Material Number = 1 b. Real Constant Number = 1 c. Element type = 1 d. There is no need to define the Element Section. e. Select Apply so you will return to the Pick Line Window.

6. Select with a left mouse click all of the steel members (2, 4, and 6). Now you are ready to define the material properties for the steel members.

7. Select OK on the Line Attributes window. The Define Line Attributes window will pop-up.

Figure 2-24 Define Line Attribute window for material 2 (steel)

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8. Define these properties for the steel members:

a. Material Number = 2 b. Real Constant = 2 c. Element Type = 1 d. Select OK. This will close both this window and the Line Attributes

window (if you haven't already done so). 9. Go to Preprocessor>Meshing>Size Controls>ManualSize>Lines> All lines.

The Element Size window will pop-up.

Figure 2-25 Element Size window

10. Set the number of divisions per line (NDIV) to 1. The other boxes should remain blank.

11. Select OK, this will close the window. Note the lines of your truss will appear shorter than before (see below):

Figure 2-26 Truss after number of divisions per element are set to 1

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Note: Be absolutely sure that your model is correct BEFORE you mesh it together (upcoming steps). You cannot place loads on your model or find displacements of nodes until it is meshed. This step is the heart of ANSYS. It might be a good idea to save your truss now.

12. Go to Preprocessor>Meshing>Mesh>Lines. The Pick Mesh Lines window will pop-up. Be sure that pick and single are selected.

Figure 2-27 Pick Mesh Lines window

13. Select each line individually with a single left click. Your mouse should look like an upward pointing arrow.

14. Once your entire truss is entirely highlighted, select OK in the Mesh lines window.

15. Your truss will now appear to be one color and connected like earlier. This is an indication that your Mesh was successful!

Figure 2-28 Fully meshed truss This completes the Preprocessing stage. Your model is now complete and is ready to be loaded. Now go to Phase 2, the Solution Phase.

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II. Solution Phase – here you will be applying loads and constraints to your truss.

A. Analysis Type 1. Go to Solution>Analysis Type>New Analysis in the Main Menu. The

Analysis Type window will pop-up.

Figure 2-29 Analysis Type window

2. Select Static and OK.

B. Apply Constraints 1. You may want to turn on your element numbering through

PlotCtrls>Numbering and setting Elem. Attrib. Numbering to Element Numbers. Next, go to Solution> Define Loads >Apply> Structural> Displacement>On Keypoints. The Apply U on KP’s window will pop-up. Be sure that Pick and Single are turned on.

Figure 2-30 Apply U on KP’s window

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2. Select node 1 (coincident with the origin) with a left click near or on the point. Doing so will highlight the point with a small yellow box.

3. In the Apply U on KP’s window, select Apply. The Define Constraints window will pop-up.

Figure 2-31 Define Constraints window

4. Set the following: a. UY b. Apply as a constant value c. Displacement value = 0 d. Leave KEXPND option as default. e. Select Apply, this will close the Define Constraints window (Figure 2-31).

Note there is now a small triangle under node 1. 5. The Apply U on KP’s window (Figure 2-30) should still be available. Now

select node 5 (far right and bottom of truss). Doing so will highlight the point with a small yellow box.

6. Select Apply. The Define Constraints window (Figure 2-31) will pop-up. 7. Select the following:

a. UX and UY b. Apply as a constant value c. Displacement = 0 d. Leave KEXPND option as default. e. Select OK, this will close the Define Constraints window and the Apply U

on KP’s window. Note there are two small triangles (one horizontal and another vertical) under node 5.

C. Apply Loads 1. Go to Solution>Define Loads>Apply>Structural>Force/Moment>On

Keypoints in the Main Menu. The Apply F/M on KP’s window will pop-up. Be sure that Pick and Single are selected.

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Figure 2-32 Apply F/M on KP’s window

2. Select node 2; it will be highlighted by a small yellow box as before. 3. Select Apply in the Apply F/M window. The Define F/M on KP’s window

will pop-up.

Figure 2-33 Define F/M on KP’s window

4. Select the following: a. FX b. Apply as constant c. Magnitude = -400 [units of lbf]. d. Select Apply. This will close the Define F/M window (Figure 2-33) but

will leave the Apply F/M window open. 5. Now select node 2 again and Apply in the Apply F/M window (Figure 2-32).

The Define F/M window (Figure 2-33) will pop-up. 6. Select the following:

a. FY b. Apply as a constant c. Magnitude = -300 [units of lbf]. d. Select OK. This will close both the Define F/M and Apply F/M windows.

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7. Repeat this process (steps 5 and 6) for node 3 (load = -1000) [units of lbf]. After doing so, your truss should look like the one below.

Figure 2-34 Fully constrained and loaded truss

D. Apply Solution 1. Now your truss is fully constrained and loaded. You are now ready to have

ANSYS actually solve the truss. Go to Solution>Solve>Current LS in the Main Menu. The Solve Current Load Step window will appear. Select OK.

Figure 2-35 Solve Current Load Step window

2. Then ANSYS will solve the truss. It may take a few seconds before both of the following windows appear. You may close them both.

Figure 2-36 Solution windows.

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This completes the Solution Phase. You are now ready for the final step, Post-processing. III. Post-processing - this is the last step of the three major analysis steps in ANSYS. In

this section we will order ANSYS to output internal member forces, member axial stresses, and node displacements. A. Reaction Forces

1. Go to General Postprocessor>List Results>Reaction Solution. In the pop-up window select All items and OK. The Reaction Solution window will pop-up.

2-37 Reaction Solution Table

2. Note that the reaction solution results are listed by node number. You can see the node numbering on your truss by going to Plot Controls>Numbering>Nodes (this may not be necessarily the same as the Keypoint numbers).

B. Member Forces and Axial Stresses

1. Go to General Postproc>Element Table>Define Table. The Define Element Table window will pop-up.

Figure 2-37 Define Element Table window

2. Select “Add...”. The Define Additional Element Table Items window will pop-up.

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Figure 2-38 Define Additional Element Table window

3. Set the following a. In the “User Label for item” box, type “Axial Stress”. b. In the left hand box scroll to the bottom and select “By sequence num”. c. In the right hand box select LS. d. Place a “1” after the comma in the Selection box in the lower right. e. Select OK. You will return to the Element Table Data Window.

4. Select “Add...”, this will launch the Additional Elements window again.

Figure 2-39 Define Additional Element Table window

5. Set the following: a. In the User label item set the name to “member forces”. b. Set “By sequence num” in the left hand box (may already be done). c. Select SMISC in the right hand box. d. Place a 1 next to SMISC in the selection box after the comma. e. Select OK. This will close the window.

6. Close element Data Table.

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7. Go to General Postproc>Elem Table> List Elem Table. The List Element Data window will pop-up.

Figure 2-40 List Element Data

8. Select Member Forces and Axial stresses by left clicking on each - the two quantities you defined. They should be at the top of the listing.

9. Select OK. This will close the window. Your element table will appear. Note how the values are listed. The element numbers are in the first column followed by the Member Forces and Axial Stresses.

Figure 2-41 Element Table

10. To output this data go to the File at the top of the window. You can save it to your EWS account or print the data (if you do not know how to do this, see Appendix, page 5-2).

11. You can also get a visual representation of your truss using some of the graphical results options. Go to General Postproc>Element Table>Plot Elem Table. The Contour Plot of Element Table window will pop-up.

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Figure 2-42 Contour Plot of Element Table window

12. In the “Item to be plotted” box (Fig. 2-42) you can choose what you would like to output. For this example we will plot member forces. Leave the lower box as “No - do not average”.

13. Click OK. This will close the window.

Figure 2-43 Contour Plot of Truss

14. You should now be able to see a deformed truss with the member forces plotted. Note that along the bottom you can see that the element forces correspond to the certain colors of the plot.

C. Displacements 1. General Postproc>Plot Results>Deformed shape. The Plot Nodal Solution

window will pop-up.

Figure 2-44 Plot Nodal Solution window

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2. Choose your plot preference; for this example plot “deformed and undeformed.” 3. Click OK. This will close the window.

Figure 2-45 Deformed and undeformed truss

4. To see the values of the deformations go to General Postproc>List Results>Nodal Solution. The Nodal Solution window will pop up.

Figure 2-46 Nodal Solution window

5. Set DOF solution in the left box and “All dofs” in the right box 6. Click OK. This will close the window and create a table of displacement results.

Figure 2-47 Displacement Table

This completes the Post-processing. You should now move on to the FRAME example.

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3. FRAME EXAMPLE As you should already know, the major difference between trusses and frames is that members are beams and thus can have a reaction moment. The following frame will be constructed:

Figure 3-1 Given Frame Once again, a complete finite element analysis in ANSYS has three components: Preprocessing, Solution, and Post-processing. This tutorial assumes that you have already worked through the truss tutorial. Consequently, procedures that are the same or very similar to those in the truss example will not be outlined in much detail. The greatest differences between the frame and truss examples occur in defining and assigning member properties and applying loads (in this case a distributed load). You will find that many of the steps in this tutorial are similar to those in the truss. I. Preprocessing

A. Introduction – think about the steps that you will complete in this section of the tutorial and how they are similar or different from the truss tutorial. The steps to be completed in this phase are listed below. 1. Modeling (similar) 2. Element Type (different - beam) 3. Real Constants (similar - cross sectional area) 4. Material Properties (similar) 5. Sections (new) 6. Meshing (similar)

B. Modeling – none of the principles used in this example are different from the truss. Try to complete this without help of the tutorial. 1. Go to Preprocessor>Modeling>Create>Keypoints>Active CS. The

coordinates for the Keypoints are:

3-1

KP No. X coord. Y coord.1 02 0 1443 1804 180 1445 3606 360 144

Table 3-1 Keypoint Locations

0

0

0

2. Connect the Keypoints with lines from Preprecessor>Modeling>Create>

Lines>Lines>Straight lines. C. Define the Element Type – this frame is composed of beams.

1. Go to Preprocessor>Element Type>Add/Edit/Delete on the Main Menu. The Define Element type window will appear.

2. Click Add... the Library of Element Types window will pop-up.

Figure 3-2 Library of Element Types Window

3. Select Beam in the left-hand box and 2D Elastic in the right. 4. Select OK. This will close the window and return you to the Element Types

window. Close this window as well. D. Define Real Constants

1. Go to Preprocessor>Real Constants>Add/Edit/Delete in the Main Menu. The Real Constants window will pop-up.

2. Select Add. Another window will appear prompting for which beam to select. You will only have one choice since you have only defined one type of beam.

3. Select OK. The Real Constants for a Beam window will appear.

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Figure 3-3 Define Real Constants for a Beam

4. In this window you define all of the constants for members 1 and 5. Real Constant set number 1 will correspond to the W8x42 beam used for members 1 and 5. Define this beam: a. Real Constant Set No. = 1 b. Cross-sectional area = 20 c. Moment of Inertia = 8000 d. Height = 8 e. Shear deflection constant = 0 f. Initial strain = 0 g. Added mass/unit length = 42 lbm/ft. = 3.5 lbm./in.

(In British units, lbf and lbm have the same numerical value.) h. Select Apply. Just like entering in Keypoint coordinates, ANSYS is now

ready to accept the constants for the second and third types of beams. Note: Remember that you are working this problem in lbf and INCHES. Often tables will report these values in other unit sets such as “Added mass/unit length” in lbm/ft. Pay close attention to your units! Also, in the British system, units of force are in lbf and units of mass are in lbm.

5. Repeat step 4 for the other two beam types with values from the following table. Once you are complete select OK and close out of the Real Constants boxes.

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Corresponding Beam W8x42 W10x48 W12x54RC Set No. 1 2 3Cross-sectional area 20 25 30Moment of intertia 8000 10000 12000Height 8 10 12Shear deflctn. constant 0 0 0Initial strain 0 0 0Added mass/unit length 3.5 4 4.5

Table 3-2 Real Constant Values

E. Define Material Properties 1. Go to Preprocessor>Material Props>Material Models in the Main Menu. The

Define Material Properties window will appear. 2. Define the material just as you defined steel or aluminum in the truss example.

Double click in right hand box Structural>Linear> Elastic>Isotropic. Enter E (EX=30000000) and Poisson's Ratio (PRXY=0.3) and Exit.

F. Define Sections – this section tells ANSYS what sort of beam you are using. In this example we will use traditional I beams. 1. Go to Preprocessor>Sections>Beam>Common Sectns. The Beam Tool

window will appear.

Figure 3-4 Beam Tool

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2. For clarity, let us have the dimensions of each beam correspond with the same Real Constant Set. For the W 8x42 beam (Real Constant set 1) enter the following: a. ID = 1 b. Name = W8x42 c. Sub Type = I (from drop-down menu) d. Offset to centroid e. W1 = W2 = W3 = 8 f. T1 = T2 = T3 = 1 g. Select Apply. This will save the information for the W 8x42 beam.

Note: all of these dimension values are expressed in units of inches.

3. Repeat step 4 for the other two beam types with values from the following table. Once you are complete select OK.

ID 1 2 3Name W8x42 W10x48 W12x54Sub Type I I IOffset Centroid Centroid CentroidW1, W2, W3 8 10 12T1, T2, T3 1 1 1

Table 3-3 Section Definitions

G. Meshing 1. Go to Preprocessor>Meshing>Size Cntrls>ManualSize>Lines>All lines in the

Main Menu. The Element Size box will appear. Set the number of divisions (ndiv) to 25. Leave the other boxes blank and select OK. Your frame will now appear to be of dashed lines.

Note: The ndiv function divides the element into small pieces, “finite elements”. For the truss, we set the number of divisions per element to 1. It was not necessary for any further divisions because in a truss there are no internal moments or rotations that need to be calculated. For this frame example (and for all structures that have members with internal forces that vary with position, such as beams) we need to be able to calculate internal moments, rotations, and other structural properties so we need several elements per part to get accurate results. Thus we have selected 25 divisions per element as a good manageable value. Also note that you could choose a different number of divisions per element. Just remember that your results may be less accurate with fewer finite elements. However, do not create too many elements as your analysis will become computationally more expensive possibly causing the program to crash or freeze. This is also why it is so important to save often while conducting your analysis and especially before Meshing!

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2. Go to Preprocessing>Meshing>Mesh Attributes>Picked lines, a select lines box will appear. Select lines 1 and 5 with a single left click. The members will be highlighted.

3. Select Apply in the pick lines box. The Line Attributes box will appear.

Figure 3-5 Line Attributes window

4. Set the following: a. Material number = 1 b. Real Constant number = 1 c. Element type number = 1 d. Element section = W8x42 e. Select Apply. This will close the Line Attributes window.

5. Repeat this process for the other members in the frame assigning the following constants:

Member No. 1 and 5 3 2 and 4Material No. 1 1 1Real Constant No. 1 2 3Element Type No. 1 1 1Element Section 1 - W8x42 2 - W10x48 3 - W12x54

Table 3-4 Line Attribute Assignments

6. It is always a good idea to save your project before meshing – do this now. 7. Go to Preprocessor>Meshing>Mesh>Lines. Select all of the lines and OK. If

the mesh was successful the frame will made of blue-green solid lines.

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II. Solution A. Introduction – the most significant change from the truss tutorial is the presence

of the distributed load. 1. Analysis Type (similar - static) 2. Define Frame Constraints (different - three fixed ends) 3. Define Frame Loads (different - distributed) 4. Apply Solution (similar)

B. Analysis Type – just like in the truss tutorial, this is a static analysis. 1. Go to Solution>Analysis Type>New Analysis in the Main Menu. The

Analysis Type window will appear. 2. Select the first option, Static, and OK.

C. Define Frame Constraints – we will fix the three bottom ends of the frame. 1. Go to Solution>Define Loads>Apply>Structural>Displacement>On

Keypoints in the Main Menu. Just as with the truss tutorial, a selection box will appear.

2. Single left click on all three bottom nodes; each will be highlighted by small yellow boxes. Select OK in the selection box. The Apply Constraints box will appear.

Figure 3-6 Apply Constraints window

3. Select All Degrees of Freedom (All DOF) since all of the free ends are fixed and constrained in the x, y and rotational directions.

4. Apply as a constant value of 0. 5. Select OK. You should see two small green triangles and little red crosses

indicating these are constrained in all three directions at each end. D. Define Frame Loads – unlike in the truss that contained all point loads, you will

need to apply a distributed load to the frame. This will be simulated by applying a load to each node. 1. Go to Solution>Define Loads>Apply>Structural>Pressure>On Beams. The

Apply Pressure on Beams selection window will appear.

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Figure 3-7 Apply Pressure on Beams selection window

2. In this case change the select style option to BOX (not Single). 3. In the workspace, highlight all of the nodes on the top of the frame where the

distributed load will be applied by enclosing this area in a box. You make the box by holding down the left mouse button and dragging.

Figure 3-8 ANSYS workspace window after the top of the frame is selected for application of a distributed load

4. Undoubtedly, you will select some of the vertical supports where you do not

want to apply the distributed load, thus you must deselect these locations. In the Apply Pressure on Beams selection window (Figure 3-7), change the Pick option (at the top) to Unpick and the Box option to Single. Then individually left click on the each small yellow box on the vertical supports where no load should be applied.

5. Once you are certain that only the nodes where the load should be applied are highlighted, select OK in the Apply F/M on Nodes window. The define pressure on beams window will appear.

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Figure 3-9 Apply Pressure on Beams window

6. Set the pressure value to 100. The other boxes may remain blank. Select OK. Remember this load was given in 100 lb/in., but you would need to convert this value if this were given in lb/ft. or other set of units!

E. Apply the Solution 1. Go to Solution>Solve>Current LS. Select Solve in the pop-up window. 2. Just as with the truss, close all of the pop-up boxes. 3. It would be a good idea to “Save As…” before Post-processing.

III. Post-processing A. Introduction – as discussed in the notes of section I.G.1 (page 3-5) recall that by

setting the number of divisions per node (ndiv = 25) we broke the beams into small pieces or “finite elements”. For most of the Post-processing functions we will use in this section, ANSYS will return data tabulated for these small pieces (finite elements) that ANSYS calls nodes. THESE NODES ARE DIFFERENT FROM KEYPOINTS. ANSYS assigns a number to each node and reports Post-processing information according to this nodal number. Before beginning your Post-processing, it is good to see the numbers assigned to each of your nodes so you can make a meaningful interpretation of this data. 1. To see you nodal numbering go to PlotCntrls>Numbering. In the numbering

window turn node numbers to ON. Select OK. For this example, the nodes at the fixed points (bottom of vertical members) are 1, 52, and 102 (from left to right respectively). You numbering might be different and is dependent upon the precise order you created lines, Keypoints, etc. Also, if you have trouble seeing your nodal numbers, you can zoom in on your model display by PlotCntrls>Pan Zoom Rotate. A tool box will appear.

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2. Take note of the nodal numbers in significant places such as those at the ends of each beam. Note that the nodal numbering will increase or decrease linearly from one end of a beam to another.

B. Reaction Forces 1. Go to General Postproc>List Results>Reaction Solution. In the pop-up

window select All items and OK. The Reaction Solution window will pop-up.

Figure 3-10 Reaction Solution window

2. You can see that the forces at node 1 (which in this example are coincident with Keypoint number 1) are 2025.4 lbf. in the x direction and 8807.9 lbf in the y direction and a moment of –76121 lbf-in. Similarly, the forces at node 102 (which corresponds to Keypoint number 5) are –2025.4 lbf in the x direction, 8807.9 lbf in the y directions and a moment of 76121 lb-in. Your solution may be somewhat different from the one given here.

3. Also note that the sum of all the reaction forces are listed at the bottom under total values. This is a good fast way to check that your model is correct. Note that the x forces sum to 0 lbs. (since none were applied), the y forces sum to 36,000 lbf (since 100lbf /in. * (180in.+180in.) = 36,000 lbf were applied) and the moments sum to 0 lbf-in.

4. If you desire, you should print these results now. See the printing section (near the end of this booklet) on how to do this.

C. Member Forces and Stresses – reporting this data is no different from the truss tutorial. See section III.B (in the Post-processing section) in the truss tutorial while keeping in mind that the output will be listed by NODE and not Keypoint as explained previously in the Reaction Forces section.

D. Member Displacements and Rotations 1. Go to General Post-processing>List Results>Nodal Solution>DOF Soln. The

List Nodal Solution window will pop-up.

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Figure 3-11 List Nodal Solution window

2. In this window select All DOFs (degrees of freedom) and OK. The solution

will appear in tabular form.

Figure 3-12 Nodal Solution Table

3. In this window, the displacement in the x and y direction and the rotation of

each node is listed. At the bottom of the list maximum values for each parameter are reported. With your nodal numbering turned on, you should be able to find the corresponding node to the Keypoint or other member location of interest.

This concludes the frame tutorial. Proceed to Chapter 4, the plate tutorial.

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4. PLATE EXAMPLE For this example we will model the plate below. Although it has a thickness, ANSYS allows us to model it as a two dimensional representation.

20” steel square plate with 4” diameter hole thickness = .1”

uniform tensile loading of 8 psi

Figure 4-1 Steel plate with hole in center When we model this plate, we will take advantage of its SYMMETRY. We can see symmetry by dividing the plate into 4 parts about the center of the hole and then apply constraints to edges of this divided part. As a rule of thumb, it is always good to take advantage of symmetry because it allows for your analysis to be smaller and subsequently more specific. Below is the geometry that we will define in ANSYS:

Figure 4-2 Model of plate that takes advantage of symmetry I. Preprocessing

A. Introduction – below is an overview of the steps we will complete in this example and how those steps compare to the previous examples:

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1. Modeling (different – defining areas and using Boolean operations) 2. Element Type (different – plate with thickness) 3. Real Constants (similar - define element thickness) 4. Material Properties (no changes here) 5. Meshing (different – mesh areas and refine mesh)

B. Modeling 1. Begin by going to: Preprocessor>Modeling>Create>Areas>Rectangle>By 2

Corners, the Create Rectangle by 2 corners window will appear.

Figure 4-3 Create Rectangle by 2 Corners window

2. The boxes WX and WY specify the coordinates of one corner of the rectangle. Enter 0 in both boxes and width and length of 10 (we will be working this problem in inches and pounds).

3. Now we must create the hole in the rectangle. Go to Preprocessor> Modeling>Create>Areas>Circle>Solid Circle. The Create Solid Circular Area window will pop up.

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Figure 4-4 Create Solid Circular Area window

4. The WP X and WP Y boxes specify the center point of the circle. Our circle will be centered at (0,0) and has a radius of 2. Your model should be as below:

Figure 4-5 Model after defining both rectangular and circular areas.

5. Just like when using a CAD program, you must perform a Boolean operation to remove the circle from the rectangle. Go to Preprocessor> Modeling>Operate>Booleans>Subtract>Areas. The Subtract Area selection window will appear.

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Figure 4-6 Subtract Area selection window

6. Single left click on the rectangle in the workspace. Be sure that you click on the area that is occupied ONLY BY THE RECTANGLE. Do not click on the area occupied by both the rectangle and the circle. The rectangle should now appear pink or purple.

7. Select OK in the Subtract Area window (Figure 4-6). You have now defined the area that we will be subtracting from.

8. Single left click on the circle in the workspace. Be sure that you click on the area occupied ONLY BY THE CIRCLE. Do not click on the area occupied by both the circle and the rectangle. The circle should now be highlighted.

9. Select OK in the Subtract Area selection window. You have now defined all of your geometry.

C. Element Type 1. Go to Preprocessor>Element Type>Add/Edit/Delete. The Define Element

Type window will appear just as in the previous tutorials (Figure 2-17). Select Add... The Element Type Library window will appear.

2. In the left hand box select Structural Solid. In the right hand box select Quad 4 node (42). This will define the elements to be small quadrilaterals each with 4 nodes from which the location of each square will be calculated.

3. Select OK. Note that the Element Types window will still be open. Be sure that the element type is highlighted and select Options. The Element Type Options window will appear:

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Figure 4-7 Element Type Options

4. In the Element Behavior box select “Plane Stress with Thk”. The other options may remain as default. Select OK and Close the Element Type window.

D. Real Constants 1. Go to Preprocessor>Real Constants>Add/Edit/Delete. The Real Constants

window will appear, select Add. A new window will appear - be sure that the correct (and only) element type is highlighted (Type 1 Plane 42) and select OK. The Define Real Constants Set window will appear.

Figure 4-8 Define Real Constants Set window

2. Keep the type number as the default (1). Set the thickness to .1. Select OK. Close out of the Real Constants windows.

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E. Material Properties - note nothing in this section has changed from previous

tutorials – try doing this on your own! 1. Go to Preprocessor>Material Props>Material Models. In the Define Material

Properties window select Structural>Linear>Elastic>Isotropic. 2. In the pop up window set the modulus of elasticity (EX) to 290000000

(remember we are working in pounds and inches so this number is in psi!) and Poisson's ratio (PRXY) to 0.3.

F. Meshing – be sure to save right now! 1. Go to Preprocessor>Meshing>MeshTool. The MeshTool box will appear.

Figure 4-9 MeshTool window

2. The MeshTool is a convenient and quick way to mesh an object and refine an object that is already meshed. Turn on the Smart Size option at the top of the MeshTool.

3. On the Fine to Coarse bar directly below the Smart Size box controls the size of your finite elements. Left click and hold down on the control bar and slide it to the right to level 8 (the level is denoted above the bar). This will make fairly large finite elements.

4. Then select Mesh (towards the bottom of the window). A Mesh Selection box will appear. Left click once on the plate geometry so that it is highlighted.

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5. Select OK in the Mesh Selection window. Now your element has been meshed and should appear to be divided into quadrilaterals.

However, we know that the most important stresses in this plate are near the hole. Consequently, we should Refine our mesh in this area. There is no need to Refine the mesh elsewhere since other stresses in the plate are not as important.

6. On the MeshTool select Refine (near the bottom of the MeshTool). Note that the MeshTool is already set to refine at elements (directly above the refine button). A Refine Selection box will appear just like the Mesh Selection box.

7. Single left click on all of the finite elements adjacent to the hole (see below).

Figure 4-10 Refining the mesh near the hole

8. Then select OK in the Refine Selection box. The Refine Mesh at Element window will pop up.

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Figure 4-11 Refine Mesh at Element

9. It is usually good to have your mesh change gradually so that you do not have disjointed elements. You can select the defaults (minimal refinement) in this window. Select OK.

Note: now the elements near the hole, where the most important and interesting stresses are located, are very small and will give a better approximation of the plate’s behavior there. The elements elsewhere in the plate are large, thus the approximation in that region will not be as accurate. However this is not cause for concern since the stresses there are unimportant and uninteresting. You might be thinking, “Why don’t I use the most accurate mesh everywhere in the element?” This is generally not a good idea because when ANSYS tries to solve the plate, it will require a large amount of memory etc. from the computer. If ANSYS requires more memory than the computer can give, then ANSYS may crash or give incomplete results.

10. Once you are satisfied with your mesh, move on to the Solution Phase. Note that you can refine your mesh several times until you have finite elements in your region of interest that are small enough to your satisfaction. You can even REFINE your mesh after you run the solution and look at post-processing output. II. Solution Phase

A. Introduction – no radically new concepts are employed in this section that were not used in previous examples. 1. Analysis Type (no changes – static) 2. Apply Constraints (similar – X and Y direction on lines) 3. Apply Pressure (similar – pressure on lines)

B. Analysis Type – go to Solution>Analysis Type>New Analysis. The New Analysis window will appear. Select Static and OK.

C. Apply Constraints 1. Go to: Solution>Define Loads>Apply>Structural>Displacement>On Lines.

The Apply Constraints window will appear. Select the bottom edge only and OK in the pick box. The Define Constraints window will appear.

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Figure 4-12 Apply Constraints window

2. Set the following: a. UY b. Apply as constant c. Displacement value = 0. d. Click on OK.

3. Repeat Steps 1 and 2 for the left edge with a zero-displacement constraint in the X direction.

D. Apply Loads

1. Go to Solution>Define Loads>Apply>Structural>Pressure>On Lines. Another pick box will appear. Select the right hand vertical line and OK. The Define Pressure on Lines box will appear.

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Figure 4-13 Apply Pressure on Lines

2. Set a constant value pressure of -8 and select OK (since negative pressure points AWAY from its application point).

E. Apply Solution - now all the loads are applied and you are ready to solve. Go to

Solution>Solve>Current LS. Select OK in the series of boxes that appear just as in the other tutorials. You are now ready for post-processing.

III. Post-processing – The major difference between post-processing with the plate and

with the other examples is that you will probably find the graphical outputs most helpful. As you might guess, tabular output will list far too many nodes to be helpful. The graphical output will likely be the easiest and most meaningful for your analysis. All graphical outputs that you will need can be accessed from:

General Postproc> Plot Results>Contour Plot>Nodal Solu.

This set of commands will output the stress, displacement, rotation, energy or any other relevant outputs. Results will be generated in the workspace. If you desire, you can refer to the Truss Example tutorial Post-processing section to review this process.

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5. APPENDIX Some common tasks such as saving, opening and printing files may be different from working in other operating systems that may already be more familiar to you. The purpose of the section is to outline these tasks to make using ANSYS easier for you. The second section outlines how to access and manipulate files on your EWS account. I. Working with ANSYS and Unix

A. Saving an ANSYS file – ANSYS is set to save files automatically to your EWS (Engineering WorkStation) account. This is ideal for your finite element analyses because several files are created throughout the analysis including the main database file (.db), a backup database file (.dbb), and various solution and results files. In order for you analysis to operate properly, it is important that all of these files be in the same location so that ANSYS can access them when necessary. The EWS account is especially convenient because you can access it from any EWS computer and you do not have the worries that are associated with using a disk (such as it being damaged or lost).

Below are a few steps to follow to save your project: 1. From the top menu bar, go to File>Save As. The Save window will appear.

You should include the file type extension which is .db. If you want to call your file “truss1”, then in the box enter: truss1.db

2. Note that you are already set to save in your EWS account. This directory is listed in the bottom box of the Save As window. For this example, let us name our file truss1.db You must include the file type extension (.db) otherwise you will not be able to see it when you want to reopen your project.

3. At the end of the account name enter and select OK. You can confirm your save was successful by going to “File>Save As” again and noting the name in the right hand box.

Note: You may also notice (especially if you have already saved projects before) that there is a file called file.db on your account. This is a default ANSYS file. If you do not specify a name for your project, all of your data will be saved into this file. It is a good idea to depend on this function only for backup purposes.

B. Open a previously saved ANSYS file 1. ANSYS uses the work “Resume” instead of “Open”. Let us say that you want

to open truss1.db. Go to File>Resume From. The Resume From window will appear.

2. You will already be in your EWS account where all of your ANSYS files should be located. Highlight truss1.db and select OK. Your project will launch.

3. If you have been saving to the default file (file.db) you can open this by simply choosing: File>Resume Jobname.db.

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C. Printing result tables 1. When you have a table window open you can choose File>Copy to Output.

This will copy the table to your project output file. 2. To view your project output file, open another xterm window and type ls at

the prompt (meaning “list”). This will list all of the files on your account. Find the file ending in .out this is the ANSYS output file and can be opened or printed using a text editor. There are several text editors available on the Unix systems. If you are unfamiliar with using a text editor you should ask the EWS site consultant on duty how to launch and use one.

D. Printing graphical outputs 1. Go to PlotCntrls>Capture Image. The “Capture Image” box will appear. 2. Select “Print to” towards the bottom of the screen. This will activate the

“Printer Name” box. 3. In the “Printer Name” box you will need to type in a Unix command to send

the job to the printer. This process may change from year to year. However at the time this tutorial was created you would type: <lpr –Pehlas3@wood.ews.uiuc.edu> for the 4th floor Engineering Hall lab and <lpr –Pmelas1@wood.ews.uiuc.edu> for the lab in MEL.. As a general rule you should type <lpr –Pprintername@wood.ews.uiuc.edu>.

II. Managing Files on your EWS Account

A. How to access all of your EWS files from a Unix machine 1. Open an xterm window. 2. At the prompt type ls this command will “list” all of the files currently saved

on your EWS account. B. Deleting files quickly – sometimes when working in ANSYS you will get a

message that there was an error saving or ANSYS could not properly execute a save command. This is probably because you do not have enough room on your EWS account to save your project. You must remove files from your account to make room for your analysis. 1. For this case, let us say that we want to remove the file paper1.doc from our

EWS account. Type rm for remove followed by the file name and its extension. For our example we would type rm paper1.doc

2. We will then be prompted if we really want to remove the file. Type y for yes.

3. Let us say that you wanted to remove all files that end with the extension .doc. Instead of removing each file individually as outlined above, type: rm *.doc The * is a “wild card” command. So, after typing this you will be prompted “if you are sure you want to remove” for each file ending in .doc individually. You can use the wildcard anywhere in the command line so you could also type: rm paper* and this would remove anything that begins with “paper” regardless of extension. When using the wildcard command you will be prompted to remove each file individually.

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III. Creating Axisymmetric Models When using ANSYS you may be asked to create an axisymmetric model. Just as mentioned in the introduction to the plate tutorial, it is always a good analysis technique to take advantage of symmetry in design. You can define geometry to be rotated about an axis, thereby taking advantage of axial symmetry. Consider the part below:

Figure 5-1 Axisymmetric bar. The y-axis is that of axial symmetry. Note the bar is also symmetric with respect to the x-axis.

You can take advantage of this symmetry in ANSYS. It was already outlined how to model traditional symmetry (which for this example is the bar’s symmetry with respect to the x axis) in the plate tutorial. To take advantage of the axial (about the y-axis) symmetry you must first model the section that is to be rotated about the y axis. Look at the wire-frame representation below:

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Figure 5-2 Wireframe representation of axisymmetric bar. Note that the section to be modeled (highlighted in gray) is entirely in quadrant I of the modeling plane (all values are non-negative). For ANSYS to properly define your geometry, you must define the section (highlighted in gray) entirely in quadrant I; you cannot allow any of this two-dimensional geometry to have negative coordinates. Also, ANSYS is programmed to rotate your element about the y axis in the workplane. Thus, if you want a solid bar (not hollow) you must align one side of your geometry on the y axis. Once your geometry is sufficiently defined, then you must tell ANSYS that the problem is axisymmetric. This is done in Preprocessing>Real Constants. See section I.C of the Plate tutorial (pg. 4-4). Follow this section as written except for steps 4 and 5. From the options window (Figure 4-7) set the Element Behavior to “Axisymmetric” (instead of “Plate with Thickness”). Then you can skip step 5 since there will be no need to define Real Constants. Be sure to constrain properly your sketch in the Solution phase. For this example, displacement will be constrained to zero in the y direction on the z axis. By specifying the elements to be “axisymmetric,” you have implicitly constrained all points on the y axis from moving in the x direction, so no explicit constraint needs to be applied.

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IV. General Notes on Understanding ANSYS When this tutorial was first used during the spring semester, 2003, the students who grasped ANSYS best seemed to understand how each step in the program fit into the overall FEA process. These students recognized that only certain operations can be performed at certain times and those operations had to be performed with a certain degree of coherence and order. Specifically, these students understood that: (1) modeling, material definition, meshing, etc. occurred only in the Preprocessing stage, and; (2) in order to edit various parts of the model, you would have to return to that analysis section to make adjustments, if possible. Because of the tedious nature of iterative design using Finite Element Analysis, it was understandably tempting to try to circumvent the rigid processes outlined in this tutorial. The students that tried this by jumping between steps or skipping sections in the tutorial often found themselves lost (with several hours wasted) trying to repair their model using processes not outlined in this tutorial. Understanding (and consequently rapid analyses!) comes with familiarizing oneself with the entire process and the order in which the processing commands must be executed.

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