Learning Forum

[Jirong]

Hi ALL,

I'm trying to use MPCHG to change material for some elements between load steps if the elements' EPELX is negative, and then go back to the solution processor and continue for a next load step. 

I found this APDL script from SimuTech website, but don't know how to use it correctly. Any suggestions?

*GET,current_loadstep,ACTIVE,,SET,LSTP ! current load step number

*IF,current_loadstep,EQ,0,then ! before first load step SOLVE

! Location of macros in user_files

FINISH

/PSEARCH,_wb_userfiles_dir(1) ! provides location of “user_files”

/SOLU

*GET,my,ACTIVE,,JOBNAM ! jobname, <= 8 characters

/DELETE,my,rdb ! if exists, req’d for single frame restart

RESCONTROL,DEFINE,NONE ! no files for multiframe restart

*ENDIF

*GET,current_loadstep,ACTIVE,,SET,LSTP ! current load step number

*IF,current_loadstep,GT,0,then ! after a load step SOLVE

FINISH

/POST1

SET,LAST ! just in case not loaded

*GET,num_elem,elem,,COUNT ! how many elements

*GET,num_elem_max,elem,,NUM,MAX ! highest element number

! example examination of results

ETABLE,my_epeq,NL,EPELX ! Example

*DEL,my_epeq,,NOPR ! delete array without warning

*DIM,my_epeq,ARRAY,num_elem_max ! array to hold strain

*VGET,my_epeq(1),ELEM,1,ETAB,my_epeq ! element table column to array

FINISH

!

/SOLU

ANTYPE,,REST ! single frame restart

! Example: make changes according to my_epeq array contents

current_elem=0

*DO,ii,1,num_elem ! step through elements

current_elem=ELNEXT(current_elem) ! next element

! create changes for this element per my_epeq(current_elem) value

! …

*ENDDO

ALLSEL

*ENDIF

! At this point, WB follows with the next SOLVE using the above settings…

Thanks,

JL

[ErKo]

HI

This is a not standard use of mechanical - we can only give some hints of what to do here.

! create changes for this element per my_epeq(current_elem) value
! 
Add an if statement at that line (see *if in the apdl manual) to check the my_eplx(current_elem) is negative.

If it is, then use the mpchg command (see apdl help manual), to change its property.

All the best

Erik

[Jirong]

Thanks for your reply!
I try to use *if statement to achieve your suggestion:
*IF,my_epeq(current_elem),LT,0,then
CMSEL,s,my_epeq(current_elem)
MPCHG, maxMaterialNumber,my_epeq(current_elem)
*ENDIF
But I got error said "Component MY_EPEQ is not defined" after *if statement was executed.Here is the error message:
*IFmy_epeq(current_elem)( = -0.300000E-01 )LT
0( =0.00000)THEN
SELECTCOMPONENT MY_EPEQ
*** ERROR ***CP =2.422TIME= 19:05:18
Component MY_EPEQ is not defined.
How to select the elements that satisfy the *if statement ? Do I need to create another array for CMSEL?

Thanks Jirong

[Felix Aschmann]

Hi Jirong CMSEL selects a component, but you haven't defined a component.
If you wanted to select the element then you need to issue the 'esel' command.
However for changing the material assigned to an element you don't have to select the element. It's sufficient to issue the MPCHG command for the element(s) you want to change.

Regards!