Reviewing results

POST1 and POST26 are for reviewing results. POST27, POST29, and POST30 have been removed; their functions are now available in POST1.

A typical POST1 session may include the following:

Reading in data from the results file
Displaying and listing the results
Error estimation
Calculations among the results data
Combining loaded cases

Reading in data from the results file

Because the solver writes results both to the database and to the results file, results data for single load step analyses are available for reviewing if you do not leave the program after solution. The SET command is still required for multiple load steps or if you leave the ansys program after solution.

Reviewing Results without SET Command

   /PREP7
   ...
   FINISH
   /SOLU
   ...
   SOLVE
   FINISH
   /POST1
   !     SET not required
   PLNSOL,...
   ...

Reviewing Results with SET Command

   /PREP7
   ...
   FINISH
   /SOLU
   ...
   SOLVE
   FINISH
   /EXIT     ! Exits program, automatically save database
   ...
   ANSYS     ! Reenters ANSYS program
   RESUME    ! Restores database
   /POST1
   SET,...   ! Reads results data from results file
   PLNSOL,...
   ...

For solids and shells, most information is now available as nodal data. You don't need an additional command to store data such as strain, thermal gradient, thermal flux, etc. For line elements (beams, pipes, spars, etc.), use ETABLE command to gain access to derived data such as stress, strain, thermal gradient, thermal flux, etc.

   /POST1
   SET,...    ! If required
   ETABLE,SMIN_I,NMISC,2   ! SMIN_I is minimum stress at node I
   ETABLE,SMAX_I,NMISC,2   ! SMAX_I is maximum stress at node I

You can list the table[PRETAB] or contour any of the table items[PLETAB]

   ***** POST1 ELEMENT TABLE LISTING *****

   STAT  CURRENT  CURRENT
   ELEM  SMAX_I   SMIN_I

     1   20667.   -19333.
     2   18667.   -17333.
     3   16667.   -15333.
     4   14667.   -13333.
     5   12667.   -11333.
    ...

Displaying and listing the results

Many commands are available in POST1 to review results:

   PLNSOL  contour plots (averaged) of nodal solution data
           (replaces PLNSTR)
   PLESOL  contour plots (unaveraged) of element solution
           data. (replaces PLNSTR,,1)
   PLETAB  contour plots (averaged or unaveraged) of
           element table data

Several types of contour plots:

   /CTYPE, 0 standard
           1 Isosurface
           2 Particle gradient
           3 Gradient triad

Result listing:

   /PRNSOL & nodal solution (replaces PRNSTR) 
   /PRESOL & element solution (replaces PRESTR) 
   /PRRSOL & reaction solution 
   /PRETAB & element table 
   /PRVECT & vector data 
   /PRPATH & path 
   /PRERR  & percentage error 
   etc.

New format controls are available for report-quality ouput:

   /HEADER  &turns on or off the page header 
   /PAGE    &defines the printout page size (number of 
            &lines and number of characters per line) 
   /FORMAT  &controls output in Fortran G, F, or E format 
   /STITLE  &defines up to four subtitles in addition to the 
                   &main title [/TITLE]

These controls are valid for PRNSOL, PRESOL, PRETAB, and PRPATH output.

Error estimation

Error estimation is available for linear analyses of both structural and thermal problems with solid or shell elements. Energy error for each element is computed by the following formula:

Where:

The nodal stress error vector is the averaged nodal stresses minus the unaveraged nodal stresses.

The percent error in energy norm is computed by:

   where e = error energy summed over selected model
         u = total strain energy over selected model

The error nomenclature is as follows:

                                  Structural  Thermal
   Energy error for each element   SERR        TERR
   Percent error in energy norm    SEPC        TEPC

PRERR command lists SEPC and TEPC for all selected elements, and PLESOL displays the contours of SERR or TERR to find out where to refine the mesh.

Calculations among results data

Calculations can be done among any results data, if that data are available in the element table [ETABLE]. The commands for calculations are the same as Rev. 4.4 - SADD, SMULT, SEXP, etc.

Combining load cases

The procedure for load case combination is new in Revision 5.0:

   LCDEF    ! Defines a load case 
   LCASE    ! Reads a load case into the database 
   LCOPER   ! Performs operations between the database 
            ! and another load case 
   LCWRITE  ! Writes the current load case to a file 
            ! (File.L01, File.L02, etc.)

For examples:

   LCDEF,1,4    ! Load case 1 points to load step 4 
   LCDEF,2,5    ! Load case 2 points to load step 5 
   LCASE,1      ! Reads load case 1 into memory 
   LCOPER,ADD,2 ! Adds load case 2 to database, store 
                ! results in the database

POST26 displays time-history results as in Rev. 4.4, but the stored data variables are changed:

   NSOL    ! For nodal solution data (replaces DISP) 
   ESOL    ! For element solution data (replaces ESTR) 
   RFORCE  ! For reaction data 
   SOLU    ! For solution summary data 
           ! (replaces ESTR,-1) 
   PLVAR   ! For graphs 
   PRVAR   ! For listings 
   EXTREM  ! To list extreme values 
   Etc.

Graph plots are enhanced in many ways:

A plot of just a curve, a curve with area under it color-filled, or an extruded (3-D) curve
User-selectable line width for the curves, grid lines, axis lines, and tick marks
User control of color for curves, area under curves, background, and grid lines
Up to 3 different Y-axis scales on a single plot
Button menu controls

Hai Tang, last updated December 15, 1995