Tutorial for ANSYS

Tutorial for ANSYS

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®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

ii 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.


iii TABLE OF CONTENTS


1. INTRODUCTION
What is ANSYS? 1-1
Helpful Web Links 1-1
Purpose of this Tutorial
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
...

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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
 
 
 
 
 
i
i
 
ACKNOWLEDGMENTS  This tutorial is based uponCosmos-Geostar Tutorialwritten 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 ofCosmos-GeoStar Tutorialinto 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?  Helpful Web Links  Purpose of this Tutorial  Using this Tutorial Effectively  Starting up in a Unix System  Default View in ANSYS  Familiarizing Yourself with ANSYS  2. TRUSS EXAMPLE  Preprocessing  Introduction  Modeling  Element Type  Real Constants  Material Properties  Meshing  Solution Phase  Analysis Type  Apply Constraints  Apply Loads  Apply Solution  Post-processing  Reaction Forces  Member Forces and Axial Stresses  Displacements  3. FRAME EXAMPLE  Preprocessing  Introduction  Modeling  Element Type  Real Constants  Material Properties  Define Sections  Meshing  Solution Phase  Introduction  Analysis Type  Define Frame Constraints  Define Frame Loads  Apply Solution
 
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1-1 1-1 1-1 1 1 -1-2 1-3 1-3 2-1 2-1 2-1 2-2 2-7 2-8 2-10 2-12 2-16 2-16 2-16 2-17 2-19 2-20 2-20 2-20 2-23 3-1 3-1 3-1 3-1 3-2 3-2 3-4 3-4 3-5 3-7 3-7 3-7 3-7 3-7 3-9
3. FRAME EXAMPLE (continued)  Post-processing  Introduction  Reaction Forces  Member Forces and Stresses  Member Displacements and Rotations  4. PLATE EXAMPLE  Preprocessing  Introduction  Modeling  Element Type  Real Constants  Material Properties  Meshing (and refining a mesh)  Solution Phase  Introduction  Analysis Type  Apply Constraints  Apply Loads  Apply Solution  Post-processing  5. APPENDIX  Working with ANSYS in Unix  Saving an ANSYS file  Opening a previously saved ANSYS file  Printing result tables  Printing graphical output  Managing your EWS Account  How to Access EWS files  Deleting EWS files in Unix  Creating Axisymmetric Models  General Notes on Understanding ANSYS    
 
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3-9 3-9  3-10 3-10 3-10 4-1 4-1 4-1  4-2 4-4 4-5 4-6 4-6 4-8 4-8 4-8 4-8 4-9 4-10 4-10 5 1 -5-1 5-1 5-1 5-2 5-2 5-2 5-2 5-2 -5 3 5-5
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.  
 
1-1
Starting up in a Unix System  After logging onto the workstation, you will see anx-termwindow (Figure 1-1) on the desktop:  
  Figure 1-1x-term window  At the prompt in this window, typeansys,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 accessesHelp.  
  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):  Figure 1-3 Session file window  1-2
 
 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 theMain  Menulocated 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
1-3
 The Main Menu is designed so that you complete the steps required to build your model bythe top of the menu and working your way downbeginning at . 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 stageIN 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 this creates a . Whilesomewhat 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)    
 
2-1
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 toModeling. Another sub-menu of all modeling commands is listed here. c. Left click the small plus sign next toCreate. 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 toKeypoints. Click the small icon next toActive 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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