ANSYSMechanicalAPDLElementReference

ANSYS Mechanical APDL Element Reference
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Table of Contents
1. About This Reference .............................................................................................................................. 1
1.1. Overview .......................................................................................................................................... 1
1.2. Conventions Used in This Reference .................................................................................................. 1
1.2.1. Applicable Products ................................................................................................................. 2
1.2.2. Product Codes ......................................................................................................................... 3
1.3. Product Capabilities .......................................................................................................................... 3
2. Element Classifications ........................................................................................................................... 5
2.1. Overview of Element Characteristics ................................................................................................. 5
2.1.1. Identifying Element Types ........................................................................................................ 5
2.1.2. 2-D vs. 3-D Elements ................................................................................................................. 5
2.1.3. Element Shape Characteristics .................................................................................................. 6
2.1.4. Element Degrees of Freedom and Discipline ............................................................................. 6
2.1.5. User-Defined Elements ............................................................................................................. 6
2.2. Summary of Element Types ............................................................................................................... 6
2.3. Selecting Elements for Your Analysis ................................................................................................ 22
2.4. Current-Technology Elements ......................................................................................................... 37
2.4.1. Legacy vs. Current Element Technologies ................................................................................ 38
2.5. Degenerated Shape Elements ......................................................................................................... 39
2.5.1. Obtaining the Best Results from Degenerated Shape Elements ............................................... 39
2.5.2. Degenerated Triangular 2-D Solid and Shell Elements ............................................................. 39
2.5.2.1.Triangular Shell Elements Are Preferred in Some Cases ................................................... 39
2.5.3. Degenerated Triangular Prism Elements ................................................................................. 40
2.5.4. Degenerated Tetrahedral Elements ......................................................................................... 40
2.5.5. Surface Stresses on Condensed Element Faces ........................................................................ 40
2.6. Special-Purpose Elements ............................................................................................................... 40
2.6.1. Superelements ....................................................................................................................... 41
2.6.2. User-Defined Elements ........................................................................................................... 41
2.7. GUI-Inaccessible Elements .............................................................................................................. 41
3. General Element Features ..................................................................................................................... 43
3.1. Element Input ................................................................................................................................. 43
3.1.1. Element Name ....................................................................................................................... 43
3.1.2. Nodes .................................................................................................................................... 43
3.1.2.1. Internal nodes ............................................................................................................... 44
3.1.3. Degrees of Freedom ............................................................................................................... 44
3.1.3.1. Internal Degrees of Freedom .......................................................................................... 44
3.1.4. Material Properties ................................................................................................................. 44
3.1.5. Special Element Features ........................................................................................................ 45
3.1.6. Sections ................................................................................................................................. 45
3.1.7. Real Constants ....................................................................................................................... 46
3.1.8. Element Loading .................................................................................................................... 46
3.1.8.1. Surface Loads ................................................................................................................ 47
3.1.8.1.1. Applying Surface Loads ......................................................................................... 47
3.1.8.1.2. Multiple Surface Loads .......................................................................................... 47
3.1.8.1.3. Surface Load Labels and Keys ................................................................................ 48
3.1.8.1.4.Tapered Surface Load ............................................................................................ 48
3.1.8.2. Body Loads .................................................................................................................... 48
3.1.8.2.1. Applying Body loads ............................................................................................. 48
3.1.8.2.2.Temperature Body Loads ....................................................................................... 49
3.1.8.3. Inertial Loads ................................................................................................................. 49
3.1.8.4. Initial Stresses ................................................................................................................ 49
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3.1.8.5. Ocean Loads .................................................................................................................. 49
3.1.9. Nodal Loading ....................................................................................................................... 49
3.1.10. Element Properties and Controls (KEYOPTs) .......................................................................... 50
3.1.10.1. Element KEYOPT Defaults ............................................................................................ 50
3.1.10.1.1. Consider Automatic Element Selection ................................................................ 50
3.1.10.1.2. KEYOPT Settings May Vary Between Products ...................................................... 50
3.2. Solution Output .............................................................................................................................. 50
3.2.1. Output File Contents .............................................................................................................. 51
3.2.2. Results File and Database Contents ......................................................................................... 51
3.2.3. Element Solution .................................................................................................................... 51
3.2.3.1.The Element Output Definitions Table ............................................................................ 52
3.2.3.2.The Item and Sequence Number Table ........................................................................... 52
3.2.3.3. Surface Loads ................................................................................................................ 53
3.2.3.4. Integration Point Solution (Output Listing Only) ............................................................. 53
3.2.3.5. Centroidal Solution (Output Listing Only) ....................................................................... 53
3.2.3.6. Element Nodal Solution ................................................................................................. 53
3.2.3.7. Element Nodal Loads ..................................................................................................... 54
3.2.3.8. Nonlinear Solutions ....................................................................................................... 54
3.2.3.9. 2-D and Axisymmetric Solutions .................................................................................... 54
3.2.3.10. Member Force Solution ................................................................................................ 54
3.2.3.11. Failure Criteria ............................................................................................................. 54
3.2.4. Nodal Solution ....................................................................................................................... 55
3.3. Coordinate Systems ........................................................................................................................ 55
3.3.1. Understanding the Element Coordinate System ...................................................................... 56
3.3.1.1. Modifying the Element Orientation ................................................................................ 56
3.3.2. Elements That Operate in the Nodal Coordinate System .......................................................... 57
3.3.3. Solution Coordinate Systems .................................................................................................. 58
4. Element Support for Material Models .................................................................................................. 59
5. Elements for Stress Analysis ................................................................................................................. 67
5.1. Continuum Stress Elements ............................................................................................................. 67
5.1.1. Stress States in 2-D Continuum Elements ................................................................................ 67
5.1.1.1. Plane Stress ................................................................................................................... 68
5.1.1.2. Plane Strain ................................................................................................................... 68
5.1.1.3. Generalized Plane Strain ................................................................................................ 68
5.1.1.4. Axisymmetric ................................................................................................................ 68
5.1.1.5. General Axisymmetric .................................................................................................... 68
5.1.1.5.1. Alternate General Axisymmetric Method for Linear Problems ................................. 69
5.1.2. Element Technologies ............................................................................................................ 69
5.1.2.1.Technologies for Lower-Order Quad and Brick Elements ................................................. 69
5.1.2.1.1. B-bar Method (Selective Reduced Integration) ....................................................... 70
5.1.2.1.2. Enhanced Strain Formulation ................................................................................ 70
5.1.2.1.3. Simplified Enhanced Strain Formulation ................................................................ 70
5.1.2.1.4. Uniform Reduced Integration ................................................................................ 70
5.1.2.2.Technologies for Lower-Order Tetrahedron Elements ...................................................... 71
5.1.2.3.Technologies for Higher-Order Quad or Brick Elements ................................................... 71
5.1.2.4.Technologies for Higher-Order Triangle or Tetrahedron Elements .................................... 71
5.1.3. Mixed u-P Formulation ........................................................................................................... 71
5.1.3.1. Overview of Mixed u-P Element Technologies ................................................................ 71
5.1.3.2. Mixed u-P Element Summary ......................................................................................... 72
5.1.3.3. Applications of Mixed u-P Formulations ......................................................................... 73
5.1.3.4. Mixed u-P Models and Overconstraint or No Unique Solution ......................................... 74
5.1.4. Generalized Plane Strain Options ............................................................................................ 74
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Element Reference

5.1.5. Axisymmetric Elements with Nonaxisymmetric Loads ............................................................. 76
5.1.5.1. General Axisymmetric Elements ..................................................................................... 76
5.1.5.1.1. Example: 3-D General Axisymmetric Model ............................................................ 79
5.1.5.2. Harmonic Axisymmetric Elements .................................................................................. 83
5.1.5.2.1. Harmonic Axisymmetric Elements with Nonaxisymmetric Loads ............................ 84
5.2. Shell Elements ................................................................................................................................ 88
5.2.1. Axisymmetric Shells ............................................................................................................... 88
5.2.2. Shell Stress and Stiffness ........................................................................................................ 88
5.2.3. Membrane and Surface Stress Options ................................................................................... 88
5.2.4. Shell Shear and Warping ......................................................................................................... 89
5.2.5. Curved Shell Elements ............................................................................................................ 89
5.2.6. Shell Element Coordinate System ........................................................................................... 89
5.2.7. Shell Element Nodes .............................................................................................................. 89
5.3. Beam and Link (Truss) Elements ...................................................................................................... 90
5.4. Pipe Elements ................................................................................................................................. 90
5.5. Reinforcing Elements ...................................................................................................................... 91
5.5.1. Discrete Reinforcing ............................................................................................................... 91
5.5.2. Smeared Reinforcing .............................................................................................................. 91
5.6. Surface Elements ............................................................................................................................ 91
5.7. Automatic Selection of Element Technologies and Formulations ...................................................... 92
5.8. Elements Under Linear Perturbation ................................................................................................ 95
5.8.1. Material Properties of Structural Elements in Linear Perturbation ............................................ 96
5.8.1.1. Specifying Material Behavior in Linear Perturbation ........................................................ 96
5.8.2. Interpretation of Structural Element Results After a Linear Perturbation Analysis ..................... 97
5.8.3. Loads, Initial Conditions, and Other Limitations in Linear Perturbation ..................................... 97
6. Elements for Multiphysics Analysis ....................................................................................................... 99
6.1. Elements for Coupled-Physics Analysis ............................................................................................ 99
6.1.1. Coupled-Field Element Classifications ..................................................................................... 99
6.1.2. Selecting Elements for Coupled-Physics Analysis ................................................................... 100
6.2. Elements for Thermal Analysis ....................................................................................................... 102
6.2.1. Thermal Elements for the Structural Region .......................................................................... 102
6.2.2.Thermal Elements for the Fluid Region .................................................................................. 103
6.2.3. Thermal Loading Elements ................................................................................................... 103
6.2.3.1. Using Thermal Surface-Loading Elements ..................................................................... 103
6.2.3.2. Using Contact Elements to Load Thermal Models ......................................................... 104
6.2.4.Thermal Control Element ...................................................................................................... 104
6.2.5. Other Elements Useful in a Thermal Analysis ......................................................................... 104
6.3. Elements for Acoustic Analysis ...................................................................................................... 104
6.3.1. Acoustic Element Types ........................................................................................................ 105
6.3.2. 3-D Acoustic Element Usage ................................................................................................. 105
6.3.3. 3-D Acoustic Element Input .................................................................................................. 105
6.3.4. 3-D Acoustic Element Input Summary ................................................................................... 108
6.3.5. 3-D Acoustic Element Item Output Data ................................................................................ 109
6.3.6. 3-D Acoustic Element Assumptions and Restrictions ............................................................. 111
6.3.7. 3-D Acoustic Element Product Restrictions ............................................................................ 112
6.4. Elements for Electric and Magnetic Analysis ................................................................................... 112
6.5. Elements for Diffusion Analysis ...................................................................................................... 114
7. Element Library ................................................................................................................................... 115
I. Element Library .................................................................................................................................... 117
5. SOLID5: 3-D Coupled-Field Solid ....................................................................................................... 119
9. INFIN9: 2-D Infinite Boundary ........................................................................................................... 129
11. LINK11: Linear Actuator .................................................................................................................. 133
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Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information
of ANSYS, Inc. and its subsidiaries and affiliates.
Element Reference