ANSYS Modeling and Meshing Guide

1 ANSYS Modeling andMeshing GuideANSYS Release 2004 ANSYS , Inc. is aUL registeredISO 9001: Modeling and Meshing GuideANSYS Release , Technology DriveCanonsburg, PA 724-746-3304(F) 724-514-9494 Copyright and Trademark InformationCopyright 2004 SAS IP, Inc. All rights reserved. Unauthorized use, distribution or duplication is , DesignSpace, CFX, DesignModeler, DesignXplorer, ANSYS Workbench environment, AI*Environment, CADOE and any and all ANSYS , Inc. productnames referenced on any media, manual or the like, are registered trademarks or trademarks of subsidiaries of ANSYS , Inc. located in the United States orother countries. ICEM CFD is a trademark licensed by ANSYS , Inc. All other trademarks and registered trademarks are property of their respective , Inc. is a UL registered ISO 9001: 2000 Inc.

2 Products may contain Patent No. 6,055, , Windows, Windows 2000 and Windows XP are registered trademarks of Microsoft and Mechanical Desktop are registered trademarks of Autodesk, is a registered trademark of SolidWorks is a registered trademark of Parametric Technology , Solid Edge and Parasolid are registered trademarks of Electronic Data Systems Corporation (EDS).ACIS and ACIS Geometric Modeler are registered trademarks of Spatial Technology, License Manager is a trademark of Macrovision ANSYS , Inc. software product and program documentation is ANSYS Confidential Information and are furnished by ANSYS , Inc. under an ANSYS software license agreement that contains provisions concerning non-disclosure, copying, length and nature of use, warranties, disclaimers and remedies,and other provisions.

3 The Program and Documentation may be used or copied only in accordance with the terms of that license the ANSYS , Inc. online documentation or the ANSYS , Inc. documentation CD for the complete Legal this is a copy of a document published by and reproduced with the permission of ANSYS , Inc., it might not reflect the organization or physical appearanceof the original. ANSYS , Inc. is not liable for any errors or omissions introduced by the copying process. Such errors are the responsibility of the partyproviding the of Contents1. Overview of Model Generation .. 1 What Is Model Generation? .. 1 Typical Steps Involved in Model Generation Within ANSYS .. 1 Comparing Solid Modeling and Direct Generation .. 1 Solid Modeling .. 1 Direct Generation .. 1 Importing Solid Models Created in CAD systems.

4 1 32. Planning Your Approach .. 2 The Importance of Planning .. 2 Determine Your Objectives .. 2 Choose a Model Type (2-D, 3-D, etc.) .. 2 Choose Between Linear and Higher Order Elements .. 2 Linear Elements (No Midside Nodes) .. 2 Quadratic Elements (Midside Nodes) .. 2 Limitations on Joining Different Elements .. 2 Find Ways to Take Advantage of Symmetry .. 2 Some Comments on Axisymmetric Structures .. 2 Some Special Requirements for Axisymmetric Models .. 2 Some Further Hints and Restrictions .. 2 Decide How Much Detail to Include .. 2 Determine the Appropriate Mesh Density .. 2 83. Coordinate Systems .. 3 Types of Coordinate Systems .. 3 Global and Local Coordinate Systems .. 3 Global Coordinate Systems .. 3 Local Coordinate Systems .. 3 The Active Coordinate System.

5 3 Surfaces .. 3 Closed Surfaces and Surface Singularities .. 3 Display Coordinate System .. 3 Nodal Coordinate Systems .. 3 Data Interpreted in the Nodal Coordinate System .. 3 Element Coordinate Systems .. 3 The Results Coordinate System .. 3 94. Using Working Planes .. 4 What Is a Working Plane? .. 4 Creating a Working Plane .. 4 Defining a New Working Plane .. 4 Controlling the Display and Style of the Working Plane .. 4 Moving the Working Plane .. 4 Rotating the Working Plane .. 4 Recreating a Previously-defined Working Plane .. 4 Working Plane Enhancements .. 4 Snap Increment .. 4 Display Grid .. 4 Retrieval Tolerance .. 4 Coordinate Type .. 4 Working Plane Tracking .. 4 55. Solid Modeling .. 5 An Overview of Solid Modeling Operations.

6 5 1 ANSYS Modeling and Meshing Guide . ANSYS Release . 002114 . SAS IP, Creating Your Solid Model from the Bottom Up .. 5 Keypoints .. 5 Hard Points .. 5 Lines .. 5 Areas .. 5 Volumes .. 5 Extruding Volumes .. 5 Sweeping Volumes .. 5 Creating Your Solid Model from the Top Down: Primitives .. 5 Creating Area Primitives .. 5 Creating Volume Primitives .. 5 Creating a Torus or Toroidal Sector .. 5 Sculpting Your Model with Boolean Operations .. 5 Boolean Operation Settings .. 5 Entity Numbering After Boolean Operations .. 5 Intersect .. 5 Illustrations of Intersection Operations .. 5 Pairwise Intersect .. 5 Illustrations of Pairwise Intersection Operations .. 5 Add .. 5 Illustrations of Addition Operations .. 5 Subtract .. 5 Illustrations of Subtraction Operations.

7 5 Working Plane Subtract .. 5 Illustrations of Working Plane Subtraction Operations .. 5 Classify .. 5 Overlap .. 5 Illustrations of Overlap Operations .. 5 Partition .. 5 Illustrations of Partition Operations .. 5 Glue (or Merge) .. 5 Illustrations of Glue Operations .. 5 Alternatives to Boolean Operations .. 5 Updating after Boolean Operations .. 5 Moving and Copying Solid Model Entities .. 5 Generating Entities from a Pattern .. 5 Generating Entities by Symmetry Reflection .. 5 Transferring a Pattern of Entities to a Coordinate System .. 5 Scaling Solid Model Entities .. 5 Solid Model Loads .. 5 Transferring Solid Model Loads .. 5 Displaying Load Symbols .. 5 Turning Off Large Symbols for Node and Keypoint Locations .. 5 Selecting a Format for the Graphical Display of Numbers.

8 5 Listing Solid Model Loads .. 5 Mass and Inertia Calculations .. 5 Considerations and Cautions for Solid Modeling .. 5 Representation of Solid Model Entities .. 5 When a Boolean Operation Fails .. 5 Degeneracies .. 5 Graphically Identifying Degeneracies .. 5 Listing the Keypoints Associated with Degeneracies .. 5 56 ANSYS Modeling and Meshing Guide . ANSYS Release . 002114 . SAS IP, Modeling and Meshing Discontinuities .. 5 Other Causes of Boolean Failures .. 5 Some Suggested Corrective Actions .. 5 Other Hints .. 5 Avoid Regions that Cross over Themselves .. 5 Use ANSYS Parameters .. 5 Consider Alternatives to Boolean Commands .. 5 Work with Lower-Dimension Constructions .. 5 Create Complex Models in Pieces .. 5 Don't Forget to SAVE .. 5 Tessellation Errors.

9 5 646. Importing Solid Models from IGES Files .. 6 Working With IGES Files .. 6 Using the SMOOTH Option .. 6 Importing IGES files using the SMOOTH Option .. 6 Guidelines for Using the SMOOTH Option .. 6 While Building the Model in the CAD System .. 6 While Writing the IGES File From the CAD Program .. 6 While Reading the IGES File into ANSYS : .. 6 While Writing an IGES File from ANSYS : .. 6 Using the FACETED Option .. 6 Repair and Enhance the Geometry .. 6 Importing IGES files using the FACETED Option .. 6 Using the Geometry Simplification Tools .. 6 Visual Inspection for Problem Features .. 6 Locating Small Features .. 6 Merging Lines .. 6 Merging Adjacent Areas .. 6 Collapsing Lines .. 6 Collapsing Areas .. 6 Splitting Lines .. 6 Splitting Areas.

10 6 Removing Area Loops .. 6 Removing Cavities and Bosses .. 6 Putting It All Together .. 6 Modeling in the FACETED Mode .. 6 Repairing Topology .. 6 Set Preferences for Gap Plotting and Listing .. 6 Finding Gaps .. 6 Deleting Geometric Entities .. 6 Merging Gaps .. 6 Repairing Incomplete Entities .. 6 Find Incomplete Boundaries .. 6 Completing Boundaries .. 6 Completing Areas .. 6 Detaching Non-manifold Entities .. 6 237. Generating the Mesh .. 7 How to Mesh Your Solid Model .. 7 Free or Mapped Mesh? .. 7 Setting Element Attributes .. 7 Creating Tables of Element Attributes .. 7 Assigning Element Attributes Before Meshing .. 7 3 ANSYS Modeling and Meshing GuideviiANSYS Modeling and Meshing Guide . ANSYS Release . 002114 . SAS IP, Assigning Attributes Directly to the Solid Model Entities.