Mechanical APDL Basic Analysis Guide

Notes

• You can define a load case by setting a pointer to a load case file with the LCFILE command (Main Menu>
  General Postproc> Load Case> Create Load Case). Then, you can use the LCASE or LCOPER commands
  to read data from the file into memory.


• You can erase any load case by issuing LCDEF,LCNO,ERASE, where LCNO is the load case number. To erase
  all load cases, issue LCDEF,ERASE. These options not only delete all load case pointers, but also delete
  the appropriate load case files (those with the default file name extensions).


• To zero the results portion of the database, issue LCZERO (Main Menu> General Postproc> Load Case>
  Zero Load Case) or LCOPER,ZERO.


• The LCABS and LCFACT commands (Main Menu> General Postproc> Load Case> Calc Options> Absolut
  Value and Main Menu> General Postproc> Load Case> Calc Options> Scale Factor), allow you to
  specify absolute values and scale factors for specific load cases. The program uses these specifications
  when you issue either LCASE or LCOPER. The program applies scale factors after it calculates absolute
  values.


• Results data read into the database from the results file (via SET or LCASE commands) will include
  boundary condition information (constraints and force loads). However, load cases read in from a load
  case file will not.Therefore, if boundary conditions appear on graphics displays after you issue an LCASE
  command (Main Menu> General Postproc> Load Case> Read Load Case), they are from a previously
  processed load case. The LCASE command does not reset the boundary condition information in memory.


• After a load case combination is performed for structural line elements, the principal stress data are not
  automatically updated in the database. Issue LCOPER,LPRIN to recalculate line element principal stresses
  based on the current component stress values.


• You can select a subset of load cases using the LCSEL command (Main Menu> General Postproc> Load
  Case> Calc Options> Sele Ld Cases). Once a subset is selected, you can use the label ALL in place of a
  load case number on load case operations.


• Element nodal forces are operated on before summing at the node.

7.3.3.2. Combining Load Cases in Harmonic Element Models

For models with harmonic elements (axisymmetric elements with nonaxisymmetric loads), the loads
are frequently applied in a series of load steps based on a Fourier decomposition (See the Element Ref-
erence). To get usable results combine the results of each load step in POST1.You can do so using load
case combinations, by saving and summing all results data at a given circumferential angle. The following
example illustrat es this procedure:

/POST1

SET,1,1,,,,90! Read load step 1 with circumferential

! angle of 90°

LCWRITE,1! Write load case 1 to load case file

SET,2,1,,,,90! Read load case 2, with circumferential

! angle of 90°

LCOPER,ADD,1! Use load case operations to add results

! from first load case to second

ESEL,S,ELEM,,1! Select element number 1

NSLE,S! Select all nodes on that element

PRNSOL,S! Calculate and list component stresses

PRNSOL,S,PRIN! Calculate and list principal

! stresses S1, S2, S3; stress intensity

! SINT; and equivalent stress SEQV

FINISH

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The General Postprocessor (POST1)