Mechanical APDL Basic Analysis Guide - Ansys

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Chapter 5: Solution lation step and go down a different path to perform inertia relief calculations. Or, you can stop at the Guyan reduction step (matrix reduction) and go on to calculate reduced eigenvalues. Some possible uses of the PSOLVE approach are listed below. • You can use the results of an intermediate solution step as input to another software package or userwritten program. • If you are interested just in inertia relief calculations or some such intermediate result, the PSOLVE approach is useful. See the Structural <strong>Analysis</strong> <strong>Guide</strong> for more information. 5.11. Singularities A singularity exists in an analysis whenever an indeterminate or non-unique solution is possible. A negative or zero equation solver pivot value will yield such a solution. In some instances, it may be desirable to continue the analysis, even though a negative or zero pivot value is encountered. You can use the PIVCHECK command to specify whether or not to stop the analysis when this occurs. The default value for the PIVCHECK command is ON. With PIVCHECK set to ON, a linear static analysis (in batch mode only) stops when a negative or zero pivot value is encountered. The message "NEGATIVE PIVOT VALUE" or "PIVOTS SET TO ZERO" is displayed. If PIVCHECK is set to OFF, the pivots are not checked. Set PIVCHECK to OFF if you want your batch mode linear static analysis to continue in spite of a zero or negative pivot value. The PIVCHECK setting has no effect for nonlinear analyses, since a negative or zero pivot value can occur for a valid analysis. When PIVCHECK is set to OFF, ANSYS automatically increases any pivot value smaller than machine "zero" to a value between 10 and 100 times that machine's "zero" value. Machine "zero" is a tiny number the machine uses to define "zero" within some tolerance. This value varies for different computers (approx1E-15). The following conditions may cause singularities in the solution process: • Insufficient constraints. • Nonlinear elements in a model (such as gaps, sliders, hinges, cables, etc.). A portion of the structure may have collapsed or may have "broken loose." • Negative values of material properties, such as DENS or C, specified in a transient thermal analysis. • Unconstrained joints. The element arrangements may cause singularities. For example, two horizontal spar elements will have an unconstrained degree of freedom in the vertical direction at the joint. A linear analysis would ignore a vertical load applied at that point. Also, consider a shell element with no in-plane rotational stiffness connected perpendicularly to a beam or pipe element. There is no in-plane rotational stiffness at the joint. A linear analysis would ignore an in-plane moment applied at that joint. • Buckling. When stress stiffening effects are negative (compressive) the structure weakens under load. If the structure weakens enough to effectively reduce the stiffness to zero or less, a singularity exists and the structure has buckled. The "NEGATIVE PIVOT VALUE - " message will be printed. • Zero Stiffness Matrix (on row or column). Both linear and nonlinear analyses will ignore an applied load if the stiffness is exactly zero. 5.12. Stopping Solution After Matrix Assembly You can terminate the solution process after the assembled global matrix file (.FULL file) has been written by using WRFULL. By doing so, the equation solution process and the process of writing data to the results file are skipped. This feature can then be used in conjunction with the HBMAT command in /AUX2 to dump any of the assembled global matrices into a new file that is written in Harwell-Boeing format. You can also use the PSMAT command in /AUX2 to copy the matrices to a postscript format that can be viewed graphically. 124 Release 13.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.
5.12. Stopping Solution After Matrix Assembly The WRFULL command is only valid for linear static, full harmonic, and full transient analyses when the sparse direct solver is selected. WRFULL is also valid for buckling and modal analyses when any mode extraction method is selected. The command is not valid for nonlinear analyses. Release 13.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates. 125
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ANSYS Mechanical APDL Basic Analysi
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Table of Contents 1. Getting Starte
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2.8.4.3. Define Material Properties
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7.2.1.6. Particle Flow and Charged
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10. Getting Started with Graphics .
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13.2.4.1.Turning Load Symbols and C
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20.8. Reviewing Contents of Binary
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List of Tables 2.1. DOF Constraints
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Chapter 1: Getting Started with ANS
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shown below define two element type
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You can choose constant, isotropic,
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You can save linear material proper
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Figure 1.4 Material Model Interface
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Figure 1.7 Data Input Dialog Box -
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The first example below is intended
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9. Click on OK. The dialog box clos
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1.1.4.9. Reading a Material Library
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If you are performing a static or f
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Chapter 2: Loading The primary obje
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Figure 2.2 Transient Load History C
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The arc-length method is an advance
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• Transferred solid loads will re
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Note If the node rotation angles th
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Figure 2.7 Scaling Temperature Cons
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Below are examples of some of the G
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Utility Menu> List> Loads> Surface>
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Figure 2.9 Example of Surface Load
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the shell, and 270° to 360° for t
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Below are examples of some of the G
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Figure 2.15 Transfers to BFK Loads
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CASE C: At least one BFV, BFA, or B
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A handy way to specify density so t
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For more information, see Initial S
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Boundary Condition Heat Flux Film C
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This problem consists of a thermal-
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2.6. Specifying Load Step Options A
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- All loads changed in later load s
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Main Menu> Preprocessor> Loads> Loa
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Command GUI Menu Paths Main Menu> S
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! Load Step 1: D, ... ! Loads SF, .
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Modeling> Create> Elements> Auto Nu
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Figure 2.22 Pretension Section Samp
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cylind,0.35,1, 0.75,1, 0,180 wpstyl
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11. Select Utility Menu> PlotCtrls>
Page 89 and 90: 24. Select Utility Menu> Plot> Comp
Page 91 and 92: Chapter 3: Using the Function Tool
Page 93 and 94: Hint: A common error is a divide-by
Page 95 and 96: 3.3. Using the Function Loader When
Page 97 and 98: 2. Define the convection boundary c
Page 99 and 100: 7. Optional: Enter comments for thi
Page 101 and 102: 3.6.1. Graphing a Function From the
Page 103 and 104: Chapter 4: Initial State The term i
Page 105 and 106: inis,defi,,,1,,100,200,150 inis,def
Page 107 and 108: applies an equal stress of SX = 100
Page 109 and 110: 4.7.2. Example: Initial Stress Prob
Page 111 and 112: inis,defi,all,all,all,all,0.1,,, in
Page 113 and 114: Chapter 5: Solution In the solution
Page 115 and 116: Solver Typical Applications * In to
Page 117 and 118: used. Running the distributed spars
Page 119 and 120: With all iterative solvers, be part
Page 121 and 122: 5.3.3. Disk Space (I/O) and Postpro
Page 123 and 124: If your analysis is either static o
Page 125 and 126: Note Whether you make changes to on
Page 127 and 128: Figure 5.2 PGR File Options From th
Page 129 and 130: GUI: Main Menu> Solution> Current L
Page 131 and 132: Figure 5.3 Examples of Time-Varying
Page 133 and 134: Requirements for Performing an Anal
Page 135 and 136: *dim,temtbl,table,4,1,,time ! Defin
Page 137 and 138: 5.9.1.1.1. Multiframe Restart Limit
Page 139: prnsol finish 5.9.2. VT Accelerator
Page 143 and 144: Chapter 6: An Overview of Postproce
Page 145 and 146: each element. Derived data are also
Page 147 and 148: Chapter 7: The General Postprocesso
Page 149 and 150: Although not required for postproce
Page 151 and 152: The ETABLE command documentation li
Page 153 and 154: • Path plots • Reaction force d
Page 155 and 156: The PLETAB command contours data st
Page 157 and 158: PLDISP,1 ! Deformed shape superimpo
Page 159 and 160: 7.2.1.6. Particle Flow and Charged
Page 161 and 162: • Particle flow traces occasional
Page 163 and 164: The surfaces you create fall into t
Page 165 and 166: You can opt to archive all defined
Page 167 and 168: 19 41.811 51.777 .00000E+00 -66.760
Page 169 and 170: Sample PRETAB and SSUM Output *****
Page 171 and 172: 7.2.5. Mapping Results onto a Path
Page 173 and 174: Command(s): PDEF GUI: Main Menu> Ge
Page 175 and 176: To retrieve path information from a
Page 177 and 178: 7.2.6. Estimating Solution Error On
Page 179 and 180: Write Results - You can use the dat
Page 181 and 182: NOTE: When you append data to your
Page 183 and 184: EMF - Windows Enhanced Metafile For
Page 185 and 186: Figure 7.20 The PGR File Options Di
Page 187 and 188: 7.4.8. Comparing Nodal Solutions Fr
Page 189 and 190: 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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