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# Help with Birth and Death and other stuff

## Help with Birth and Death and other stuff

(OP)
Hello again!
I am having some problems regarding my thesis' simulation, so I am looking forward to any help! I have some questions that I am about to make, but first, I think I should explain what I am trying to do:
I want to simulate what we call butt-welding, so I have to plot many weld beads, side by side, and then some above them. I will use a moving heat source to simulate the welding arc, which inputs heat to the plate. The moving heat source is already working, but I need some help to continue this work.

1) Using Birth and Death (EALIVE and EKILL)
I am having some problem with this part. The ideal thing would be to plot the weld bead as the heat source moves, or/and when its elements achieve around 1450 °C (Fe-C steel fusion temperature, for a SAE 1020 or around it). I tried a snippet I've found on the internet but it doesn't works, or I am not using it right. My code is shown below, followed by the Birth and Death snippet I've found.

#### CODE --> APDL

ET,1,SOLID70

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

AUTOTS,ON

TIME_WELD=200
DT=1
A=0.003  !A, B and C's are the heat source dimentions (meters)
B=0.004
C1=0.004
C2=0.016
TAU=0 ! Time delay to control the heat source position at t0 (0 seconds)
FF=0.4 ! FF and FR are the power distribution in the front side and rear side of the heat source, respectively
FR=1.6
Q=3840 ! Power input (Watts)
VEL=0.002 ! Welding speed
EE=2.71 ! Euler number, I had to set it as 2.71 instead of using exp() due to some problems I was experiencing

NPT=TIME_WELD/DT

*DO,ii,1,NPT,1
WTIME=(ii/2)
TIME,WTIME

HCENTER=VEL*WTIME

*DO,jj,EMIN,EMAX,1

X=CENTRX(jj)
Y=CENTRY(jj)
Z=CENTRZ(jj)

CSI=Z+(VEL*(TAU-WTIME)) ! This is what controls the position of the heat source, through the axis Z, over time

*IF,Z,GT,HCENTER,THEN ! Attributes C1 and FF to the front part of the heat source and C2 and FR to the rear side of the heat source

C=C1
F=FF

*ELSE

C=C2
F=FR

*ENDIF

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

QF=PART1*PART2 ! Double ellipsoid heat source equation

BFE,jj,HGEN,,QF

*ENDDO
OUTRES,ESOL,ALL,
SOLVE

*ENDDO

CMSEL,ALL
BFEDELE,ALL,ALL
ALLSEL 
Here's the snippet

#### CODE

/post1                    ! Enter postprocessor
set,last                  ! Read in last subset of data
etable,melty,temp,        ! Create an element table
esel,s,etab,melty,1450    ! Select all elements from table above 1450
finish
/solu                     ! Re-enter solution phase
antype,,rest              ! Restart analysis
ekill,all                 ! Kill all selected elements
esel,all                  ! Re-select all elements
finish
/post1                    ! Re-enter postprocessor
set,last                  ! Read in last subset of data
esel,s,live               ! Select all live elements
plnsol,temp               ! Plot the temp contour of the live elements 

How can I make this work? Have you any other idea?

2) I simply can't position the heat source in any other coordinate system other than the global one, I don't know why, and I really need to know how to! The heat source always starts in (0,0,0) from the global coordinate system, and moves through the Z coordinate, as it should, but I can't make the heat source start from any other coordinate system... any clue?

3) How can I make a convection as a function of the temperature? Or how can I make a heat loss based on the temperature of the plate?

Any help would be REALLY, REALLY APPRECIATED!

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