Learning Forum

[Gabriela]

I am trying to use "Element Birth and Death" technique with a moving heat source in a welding model in workbench.

Basically I divide the weld line in a few parts, and I activate (birth) each part in different time, but I cannot move the heat source through the parts. (The moving heat source script, without the birth and death technique, is working). 

[Bill Bulat]

Hello Gabriela In your APDL it appears you are applying heat associated with the welding process as a body load (BFE command with the HGEN label). One problem might be that if you are inadvertently trying to apply heat to deactivated elements, the heat will not be used because element loads applied to deactivated elements are zeroed out of the load vector:

But perhaps, before delving into details, we should clarify your analysis objectives. It isn't clear to me if you are trying to simulate the addition of filler metal to the parent material (as would happen in arc welding with an electrode), of if you are instead trying to simulate the melting of parent material without addition of a filler material (I believe this is the case for laser welding). Also, I don't know if you intend to transfer the thermal results to a structural system (perhaps to calculate residual stresses within and near the heat effected zone?).
The attached project archive illustrates a simulation of a hypothetical laser weld operation (transient thermal calculations only). Element birth and death is not used. Heat is applied continuously to element faces along a circular joint using surface effect elements rather than to the volume of the parent metals. Note that radiation and convection heat transfer are included in the model. One thing missing in this model is the latent heat of fusion which should be modeled using the enthalpy material property in Engineering Data.
Kind regards Bill

[Gabriela]

Mr Bill thank you for your reply!!!

Indeed, I am applying the heat as body load (BFE). First I deactivated all the elements of the weld line (CMSEL,S,Weld -> EKILL, all) and then I activate each part before applying the heat, as I have posted before (CMSEL,S,Weld1 -> EALIVE,Weld1 ... BFE...). But could maybe the program not read in that order?

Yes, I am trying to simulate the addition of filler metal to the parent material. And yes, I intend to transfer the thermal results to a structural system to calculate residual stresses.
Actually, I already did this before WITHOUT implement the "element birth and death technique" - The heat source was moving and I was able to transfer the results to a structural system.

And I also included radiation and convection in the model, I just suppressed radiation because seems show some error that I couldn't solve yet when I implement the birth and death technique.
Thank you for tell me about the enthalpy property, I hadn't really added this property before.

Is this information enough for maybe you help me?
Kind regards,
Gabriela

[mkalel]

I am having the same problem. Did you able to solve the APDL issue? let me know

thanks mukesh

[Gabriela]

No. I tried a lot, but stayed stuck there.

[Jayesh]

In Ansys workbench, I also found that moviding heat source is unable to consider birth and death elements. Is there any APDL commands to apply birth and death elements to moving heat source?

[atello28]

I am using the code below and I experience the same problem as Gabriela
I can have welding done in WELD1, but it is not possible to continue welding in WELD2.
WELD contains both WELD1 and WELD2.

Can anybody give some advice?


CMSEL,S,WELD
EKILL,ALL

!FIRST WELD FIRST SECOND

CMSEL,S,WELD1
EALIVE,WELD1


CMSEL,ALL
*GET,EMAX,ELEM,,NUM,MAX
*GET,EMIN,ELEM,,NUM,MIN
ALLSEL

TIME_WELD=6
DT=0.1
A=0.005
B=0.005
C1=0.005
C2=0.015
TAU=0
FF=0.5
FR=1.5
Q=1500
VEL=5e-3

NPT=TIME_WELD/DT
NROPT, FULL


*DO,i,1,NPT,1
WTIME=(i/10)
TIME,WTIME+0*TIME_WELD

HCENTER=VEL*WTIME


*DO,jj,EMIN,EMAX,1

*GET, X, elem, jj, cent, X
*GET, Y, elem, jj, cent, Y
*GET, Z, elem, jj, cent, Z



CSI=Y+VEL*(TAU-WTIME)


*IF,Y,GT,HCENTER,THEN

C=C1
F=FF

*ELSE

C=C2
F=FR

*ENDIF

PART1=(6*(3**0.5)*F*Q)/(A*B*C*3.14*(3.14**0.5))
PART2=(exp(-3*(Z/A)**2))*(exp(-3*(X/B)**2))*(exp(-3*(CSI/C)**2))

QF=PART1*PART2


BFE,jj,HGEN,,QF

*ENDDO

SOLVE

*ENDDO

CMSEL,ALL
BFEDELE,ALL,ALL
ALLSEL


!SECOND WELD SECOND SECOND

CMSEL,S,WELD2
EALIVE,WELD2



*DO,i,1,NPT,1
WTIME=(i/10)
TIME,WTIME+1*TIME_WELD

HCENTER=VEL*WTIME



*DO,jj,EMIN,EMAX,1

*GET, X, elem, jj, cent, X
*GET, Y, elem, jj, cent, Y
*GET, Z, elem, jj, cent, Z


CSI=Y+VEL*(TAU-WTIME)


*IF,Y,GT,HCENTER,THEN

C=C1
F=FF

*ELSE

C=C2
F=FR

*ENDIF

PART1=(6*(3**0.5)*F*Q)/(A*B*C*3.14*(3.14**0.5))
PART2=(exp(-3*(Z/A)**2))*(exp(-3*(X/B)**2))*(exp(-3*(CSI/C)**2))

QF=PART1*PART2


BFE,jj,HGEN,,QF

*ENDDO

SOLVE

*ENDDO

CMSEL,ALL
BFEDELE,ALL,ALL
ALLSEL