Learning Forum

[John Miller]

Hello,

I’m facing a problem during an AM simulation (transient thermal).

In this simulation, the extruded material is killed initially and then subsequently extruded with ealive.

It’s working just fine.

This is the basic model, but I have to use /prep7 in combination with a single frame restart.

Setting up this is also not extremely difficult, but now the element kill is not working anymore.

Without restarting, this works:

 

nropt,full

/prep7

cmsel,s,path

ekill,all

finish

/solu

 

But with restart, because of the rdb data, this isn’t working anymore.

The first step looks okay:

The second step is also okay:

 

The third step is wrong, only the first extruded Volume is still alive, and all activated elements of the second step are killed.

Only the first step is okay and all other steps are wrong. The former extruded elements via ealive are killed. The prep7 is working in every step/load step.

Is there a way to kill only initially the elements with inistate for example or other commands?

 

With best regards

John

[Dave Looman]

It's better to not leave solution if you don't have to.  EKILL/EALIVE can be done in solution for example.  One issue with restarts is there is an internal resume of a database saved at the start of solution.  That can destroy parameter definitions and other model information created after the start of solution.  A possible workaround might be to save the database before the restart command and resume it afterwards.

[John Miller]

 

 

 

Hello Dave,

 

thank you for your response. You are right, it’s better to stay in /solu, but the model is forcing me to do so. Without leaving the solution, it’s not difficult to achieve a material extrusion for AM Process with the aid of ekill and ealive. I simplified my model to make it more clear how it works.

The Problem with my model is that I need the current surface for radiation application. You can see it in the picture below. During material extrusion via ealive the current surface is constantly changing, which makes it difficult to use the GUI radiation dialogue. For this, you can use only the final exterior surface, but this is not the exterior surface during the material extrusion. During extrusion with ealive the inner elements/nodes become currently exterior and after a few lines interior.

Without restarting it looks like this (for the 6^th time step):

With restart that’s the result (for the 6^th time step):

 

The code of the two APDL snippets I use looks like this:

Command object 1 (“initial_ekill) for the element deletion of the volume to be generated:
Code:
________________________________________
nropt,full
/prep7
cmsel,s,path
ekill,all
finish
/solu
________________________________________

This kills the element of the “path”, which is the volume to be generated step by step via ealive.

Without restarting it works fine, because the /prep7 is only called one time.

Command object 2 (“AM_process”) for the element seletion of the volume to be generated:

Code:
________________________________________

tintp,,,,1.0
nropt,full
! Parameter
t=1
….
…
*do,iijj,….! Outer loop for AM phase iii =1 and cooling phase iii=2
*if,iijj,….
*do,i,… ! AM loop with ealive
/GOPR

! Force Single Frame restart
rescontrol,none

! Deleting the temperature from the previous time step
cmsel,s,path,node
cm,Tload,node
ddele,…

! Element activation for the newly extruded volume
esel,r,…
…
cm,alive,elem
ealive,alive

! Applying the thermal load (temperature) to the volume/node activated by ealive
cmsel,s,path,node
nsel,r,…
…
cm,load,node
D,load,temp,TL
! Select external nodes

/com,*****************************Currently External Nodes*****************************
cmsel,s,path,elem
esel,r,…
nsel,s,…
cmsel,u,…
cm,external,node
/com,******************************************************************************

! Constant print bed temperature
nsel,none
esel,none
cmsel,s,…
cm,bednodes,node
D,bednodes,temp,Tbed

allsel,all
outres,all

Time,i*dt
solve

! Excursion into the preprocessor for the creation of surf152 elements for convection and radiation
/prep7
/GOPR
/com,Start surf152 for convection
esel,s,….
….
….
esurf
allsel,all

/com,End surf152 generation for convection

! Restart of solution phase
/solu
trnopt,full
nropt,full
thopt,full
antype,,restart

! Application of the thermal load on surf152 elements
esel,s,ename,,152
…
allsel,all
outres,all,all
*enddo
! cooling
*elseif,iijj,…

/com,****************************Cooling Step***********************************
/GOPR

…
allsel,all
outres,all,all
*do,jjj,…
/GOPR
…
solve
*enddo
/com,******************************************************************************
*else
*endif
*enddo

 

The database must be saved in this way so that initially the body “path” is killed and during the AM process the former generated volume, because of a former step won’t be deleted.

I thought about using:

/config,noeldb,0 !

to write results into the database.

 

With best regards

John

 

 

 

[Dave Looman]

I've never had to update radiation definition during solution so I probably can't appreciate the difficulties of doing that, but I haven't seen any APDL commands in your scripts that can't be issued in solution.

  /config,noeldb,0 is frequently needed when modifying the model during solution.  Probably also should use shared memory (not distributed) parallel when accessing current results during solution.

[John Miller]

Hello Dave,

thank you for your answer.

When I use /config,noeldb,0 whether in /prep7 or /solu I get always

*** WARNING ***                         CP =       3.703   TIME= 15:12:16
 /CONFIG is not a recognized SOLUTION command, abbreviation, or macro.  

 

  This command will be ignored.  

or

 *** WARNING ***                         CP =       3.078   TIME= 15:06:54
 /CONFIG is not a recognized PREP7 command, abbreviation, or macro.     
  This command will be ignored.                                         
 Ende surf152 for Radiation

Maybe that’s not the right way. Perhaps the save command is more promising

 

With best regrads

John

[John Miller]

 

Hello Dave,

thank you for your answer.

When I use /config,noeldb,0 whether in /prep7 or /solu I get always

*** WARNING ***                         CP =       3.703   TIME= 15:12:16
 /CONFIG is not a recognized SOLUTION command, abbreviation, or macro.  

 

  This command will be ignored.  

or

 *** WARNING ***                         CP =       3.078   TIME= 15:06:54
 /CONFIG is not a recognized PREP7 command, abbreviation, or macro.     
  This command will be ignored.                                         
 Ende surf152 for Radiation

Maybe that’s not the right way. Perhaps the save command is more promising

 

With best regrads

John

 

[Dave Looman]

/config is a "Session" command so needs to be issued outside modules like PREP7 and SOLU.  If you are in a module issue finish to leave the module and then /solu or /prep7 to reenter the module:

finish

/config,noeldb,0

/solu

 

 

[John Miller]

 

 

Hello Dave,

thanks for the hint.

I used /config,noeldb,0 after the solve right before I leave /solu and enter /prep7, unfortunately I didn’t change anything.

 

…

D,bednodes,temp,Tbed

allsel,all
outres,all

Time,i*dt
solve

save

finish
/config,noeldb,0

/prep7
/GOPR  
/com,Start surf152 for radiation

esel,s,….
….
….
esurf
allsel,all

/com,End surf152 generation for radiation

! Restart of solution phase
/solu

…

 

If I plot the Temperature of the AM process I discovered something strange, the first three time steps are looking good. Material is extruded and then with the 4th time step the activation of the elements is no longer correct, suddenly elements are deleted again. I do not understand why 

Step 1

 

Step 2

 

Step 3

 

Step 4

 

Step 5

Step 6

Step 7

Step 8

Step 9

Step 10

Step 11

Step 12

 

With best regards

John

 

 

[Dave Looman]

So the process is to gradually ealive additional elements, but starting in load step 4 some of them go back to being dead?  I've never seen that happen on it's own, but perhaps the restart issue I mentioned could set the status of an element back to a previous status.  

[John Miller]

Hello Dave,

 

neither do I understand why this is happening nor how to fix this?

Is it possible to update the restart database (for single frame restart) after each step?

 

With best regards

John

 

[Dave Looman]

Earlier I proposed issuing save,model,db and resume,model,db before and after the antype,,restart.  I don't know if that would help or not.

 

[John Miller]

Hello Dave,

if I place the save and resume command before and afrter the restart I get this result.

It's even worse than before.

The script looks like this:

tintp, , , , 1.0
nropt, full

finish
/ config, noeldb, 0
/ solu
...
Parameter
...
*do, iijj,...
* if, iijj, ...
*do, i,...
/ GOPR
rescontrol, none
...
cm, alive, elem
ealive, alive

...
cm, load, node

D, load, temp, TL

/ com, Currently External Nodes
cmsel, ...
...
cm, external, node
nsel, stat
esel, stat
/ com, Ende Currently External Nodes

ddele, external, temp,            
d, external, temp, Tsurf          
...
allsel, all
outres, all

Time, ...
solve

/ prep7
/ GOPR
/ com, Start surf152 for radiation
...
esurf                        
esel, stat
nsel, stat
allsel, all
/ com, End surf152 for radiation

save, model, db

/ solu
trnopt, full
nropt, full
thopt, full

antype, , restart

finish
resume, model, db
/solu
...
further things
..
allsel, all
outres, all, all
*enddo

*elseif, iijj,...
/ com, Start cooling Step
/ GOPR
...

ddele, ...

...
D, bednodes, temp, Tbed

allsel, all
outres, all, all

*do, jjj, ...
/ GOPR
...
Time, ...
solve
*enddo
/ com, Ende cooling step

*else
*endif
*enddo

/ prep7
!optional:
*create, solve, mac
/ com, Skip 'Solve'
*end