Mechanical APDL Basic Analysis Guide - Ansys

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Chapter 2: Loading Figure 2.3 Load Steps, Substeps, and Equilibrium Iterations �� 2.3. The Role of Time in Tracking �� The ANSYS program uses time as a tracking parameter in all static and transient analyses, whether they are or are not truly time-dependent. The advantage of this is that you can use one consistent "counter" or "tracker" in all cases, eliminating the need for analysis-dependent terminology. Moreover, time always increases monotonically, and most things in nature happen over a period of time, however brief the period may be. Obviously, in a transient analysis or in a rate-dependent static analysis (creep or viscoplasticity), time represents actual, chronological time in seconds, minutes, or hours. You assign the time at the end of each load step (using the TIME command) while specifying the load history curve. To assign time, use one of the following: Command(s): TIME GUI: Main Menu> Preprocessor> Loads> Load Step Opts> Time/Frequenc> Time and Substps Main Menu> Preprocessor> Loads> Load Step Opts> Time/Frequenc> Time - Time Step Main Menu> Solution> Analysis Type> Sol'n Control ( : Basic Tab) Main Menu> Solution> Load Step Opts> Time/Frequenc> Time and Substps Main Menu> Solution> Load Step Opts> Time/Frequenc> Time - Time Step Main Menu> Solution> Load Step Opts> Time/Frequenc> Time and Substps Main Menu> Solution> Load Step Opts> Time /Frequenc> Time - Time Step In a rate-independent analysis, however, time simply becomes a counter that identifies load steps and substeps. By default, the program automatically assigns time = 1.0 at the end of load step 1, time = 2.0 at the end of load step 2, and so on. Any substeps within a load step will be assigned the appropriate, linearly interpolated time value. By assigning your own time values in such analyses, you can establish your own tracking parameter. For example, if a load of 100 units is to be applied incrementally over one load step, you can specify time at the end of that load step to be 100, so that the load and time values are synchronous. In the postprocessor, then, if you obtain a graph of deflection versus time, it means the same as deflection versus load. This technique is useful, for instance, in a large-deflection buckling analysis where the objective may be to track the deflection of the structure as it is incrementally loaded. Time takes on yet another meaning when you use the arc-length method in your solution. In this case, time equals the value of time at the beginning of a load step, plus the value of the arc-length load factor (the multiplier on the currently applied loads). ALLF does not have to be monotonically increasing (that is, it can increase, decrease, or even become negative), and it is reset to zero at the beginning of each load step. As a result, time is not considered a "counter" in arc-length solutions. 24 Release 13.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.
The arc-length method is an advanced solution technique. For more information about using it, see "Nonlinear Structural Analysis" in the Structural Analysis Guide. A load step is a set of loads applied over a given time span. Substeps are time points within a load step at which intermediate solutions are calculated. The difference in time between two successive substeps can be called a time step or time increment. Equilibrium iterations are iterative solutions calculated at a given time point purely for convergence purposes. 2.4. Stepped Versus Ramped Loads When you specify more than one substep in a load step, the question of whether the loads should be stepped or ramped arises. • If a load is stepped, then its full value is applied at the first substep and stays constant for the rest of the load step. • If a load is ramped, then its value increases gradually at each substep, with the full value occurring at the end of the load step. Figure 2.4 Stepped Versus Ramped Loads �� The KBC command (, Main Menu> Solution> Load Step Opts> Time/Frequenc> Freq & Substeps: Transient Tab / Main Menu> Solution> Load Step Opts> Time/Frequenc> Time and Substps / Main Menu> Solution> Load Step Opts > Time/Frequenc> Time & Time Step, or Main Menu> Solution> Load Step Opts> Time/Frequenc> Freq & Substeps / Main Menu> Solution> Load Step Opts> Time/Frequenc> Time and Substps / Main Menu> Solution> Load Step Opts> Time/Frequenc> Time & Time Step) is used to indicate whether loads are ramped or stepped. KBC,0 indicates ramped loads, and KBC,1 indicates stepped loads. The default depends on the discipline and type of analysis. Load step options is a collective name given to options that control load application, such as time, number of substeps, the time step, and stepping or ramping of loads. Other types of load step options include convergence tolerances (used in nonlinear analyses), damping specifications in a structural analysis, and output controls. Release 13.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates. 2.4. Stepped Versus Ramped Loads � �� 25
Page 1 and 2: ANSYS Mechanical APDL Basic Analysi
Page 3 and 4: Table of Contents 1. Getting Starte
Page 5 and 6: 2.8.4.3. Define Material Properties
Page 7 and 8: 7.2.1.6. Particle Flow and Charged
Page 9 and 10: 10. Getting Started with Graphics .
Page 11 and 12: 13.2.4.1.Turning Load Symbols and C
Page 13 and 14: 20.8. Reviewing Contents of Binary
Page 15 and 16: List of Tables 2.1. DOF Constraints
Page 17 and 18: Chapter 1: Getting Started with ANS
Page 19 and 20: shown below define two element type
Page 21 and 22: You can choose constant, isotropic,
Page 23 and 24: You can save linear material proper
Page 25 and 26: Figure 1.4 Material Model Interface
Page 27 and 28: Figure 1.7 Data Input Dialog Box -
Page 29 and 30: The first example below is intended
Page 31 and 32: 9. Click on OK. The dialog box clos
Page 33 and 34: 1.1.4.9. Reading a Material Library
Page 35 and 36: If you are performing a static or f
Page 37 and 38: Chapter 2: Loading The primary obje
Page 39: Figure 2.2 Transient Load History C
Page 43 and 44: • Transferred solid loads will re
Page 45 and 46: Note If the node rotation angles th
Page 47 and 48: Figure 2.7 Scaling Temperature Cons
Page 49 and 50: Below are examples of some of the G
Page 51 and 52: Utility Menu> List> Loads> Surface>
Page 53 and 54: Figure 2.9 Example of Surface Load
Page 55 and 56: the shell, and 270° to 360° for t
Page 57 and 58: Below are examples of some of the G
Page 59 and 60: Figure 2.15 Transfers to BFK Loads
Page 61 and 62: CASE C: At least one BFV, BFA, or B
Page 63 and 64: A handy way to specify density so t
Page 65 and 66: For more information, see Initial S
Page 67 and 68: Boundary Condition Heat Flux Film C
Page 69 and 70: This problem consists of a thermal-
Page 71 and 72: 2.6. Specifying Load Step Options A
Page 73 and 74: - All loads changed in later load s
Page 75 and 76: Main Menu> Preprocessor> Loads> Loa
Page 77 and 78: Command GUI Menu Paths Main Menu> S
Page 79 and 80: ! Load Step 1: D, ... ! Loads SF, .
Page 81 and 82: Modeling> Create> Elements> Auto Nu
Page 83 and 84: Figure 2.22 Pretension Section Samp
Page 85 and 86: cylind,0.35,1, 0.75,1, 0,180 wpstyl
Page 87 and 88: 11. Select Utility Menu> PlotCtrls>
Page 89 and 90: 24. Select Utility Menu> Plot> Comp
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Chapter 3: Using the Function Tool
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Hint: A common error is a divide-by
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3.3. Using the Function Loader When
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2. Define the convection boundary c
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7. Optional: Enter comments for thi
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3.6.1. Graphing a Function From the
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Chapter 4: Initial State The term i
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inis,defi,,,1,,100,200,150 inis,def
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applies an equal stress of SX = 100
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4.7.2. Example: Initial Stress Prob
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inis,defi,all,all,all,all,0.1,,, in
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Chapter 5: Solution In the solution
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Solver Typical Applications * In to
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used. Running the distributed spars
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With all iterative solvers, be part
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5.3.3. Disk Space (I/O) and Postpro
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If your analysis is either static o
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Note Whether you make changes to on
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Figure 5.2 PGR File Options From th
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GUI: Main Menu> Solution> Current L
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Figure 5.3 Examples of Time-Varying
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Requirements for Performing an Anal
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*dim,temtbl,table,4,1,,time ! Defin
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5.9.1.1.1. Multiframe Restart Limit
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prnsol finish 5.9.2. VT Accelerator
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5.12. Stopping Solution After Matri
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Chapter 6: An Overview of Postproce
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each element. Derived data are also
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Chapter 7: The General Postprocesso
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Although not required for postproce
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The ETABLE command documentation li
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• Path plots • Reaction force d
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The PLETAB command contours data st
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PLDISP,1 ! Deformed shape superimpo
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7.2.1.6. Particle Flow and Charged
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• Particle flow traces occasional
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The surfaces you create fall into t
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You can opt to archive all defined
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19 41.811 51.777 .00000E+00 -66.760
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Sample PRETAB and SSUM Output *****
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7.2.5. Mapping Results onto a Path
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Command(s): PDEF GUI: Main Menu> Ge
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To retrieve path information from a
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7.2.6. Estimating Solution Error On
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Write Results - You can use the dat
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NOTE: When you append data to your
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EMF - Windows Enhanced Metafile For
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Figure 7.20 The PGR File Options Di
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7.4.8. Comparing Nodal Solutions Fr
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the effect of the rigid body rotati
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The SADD command (Main Menu> Genera
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To view correct mid-surface results
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To get usable results combine the r
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7.4.4. Mapping Results onto a Diffe
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• EMF (Main Menu> General Postpro
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7.4.8.1. Matching the Nodes The Mec
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7.4.8. Comparing Nodal Solutions Fr
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Chapter 8: The Time-History Postpro
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enables the alternate selections sh
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1. Click on the Add Data button. Re
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APPEND Appends data to previously s
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!derivative of variable 2 with resp
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The above command assumes that you
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When plotting complex data such as
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Sample Output from EXTREM time-hist
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5. Select the variables to be opera
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RESP requires two previously define
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Chapter 9: Selecting and Components
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Note Crossover commands for selecti
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would put UX and UZ constraints on
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The Command Reference describes the
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Chapter 10: Getting Started with Gr
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Remote Network Access Hidden Line R
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10.4.1. Adjusting Input Focus To en
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• If the environment variable SB_
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10.5.5. Erasing the Current Display
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Chapter 11: General Graphics Specif
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11.3.1. Changing the Viewing Direct
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11.4. Controlling Miscellaneous Tex
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11.4.3. Controlling the Location of
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Chapter 12: PowerGraphics Two metho
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The subgrid approach affects both t
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Chapter 13: Creating Geometry Displ
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Figure 13.1 Element Plot of SOLID65
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13.2.1.12. Vector Versus Raster Mod
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Figure 13.2 Create Best Quality Ima
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13.2.3.2. Choosing a Format for the
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Chapter 14: Creating Geometric Resu
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Figure 14.2 A Typical ANSYS Results
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• Changing the contour interval.
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14.5. Isosurface Techniques Isosurf
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Chapter 15: Creating Graphs If you
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Establishing separate Y-axis scales
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15.2.3.5. Defining the TIME (or, Fo
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Chapter 16: Annotation A common ste
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16.3. 3-D Annotation 3-D text and g
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Chapter 17: Animation Animation is
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• ANMODE (Utility Menu> PlotCtrls
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Figure 17.2 The Animation Controlle
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Note If you are doing animation fro
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Chapter 18: External Graphics Besid
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18.1.4. Exporting Graphics in UNIX
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Note The commands discussed in this
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18.3.6. Editing the Neutral Graphic
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Chapter 19: The Report Generator Th
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2. Specify a caption for the captur
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19.4.1.1. Creating a Custom Table I
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Table ID 46 47 48 Description Compo
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Button or Field DYNAMIC DATA REPORT
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The HTML tag to begin JavaScript co
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listingName A unique listing name a
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Chapter 20: File Management and Fil
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20.4. Text Versus Binary Files Depe
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Identifier ELEM EMAT ERR ESAV FATG
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20.4.3. File Compression Many file
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You can also redirect graphics outp
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Chapter 21: Memory Management and C
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21.3.3. Changing Database Space Fro
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Figure 21.4 Dividing Work Space ANS
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NUM_BUFR is the number of buffers p
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een chosen for efficient running of
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Index Symbols 3-D graphics devices,
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path plots, 142 POST26 graphs, 200
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fatigue graphs, 257 files, 277 focu
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material model interface, 8 materia
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multiframe, 117 restarting an analy
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WINDOW command, 227 Windows graphic
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