Single-Pass Welding Simulation in Abaqus Using Birth and Death Method

Learn how to simulate single-pass welding on a flat plate in
Abaqus using the birth and death technique for element activation
and a Fortran DEFLUX subroutine to model the moving heat source.
This step-by-step Abaqus guide is perfect for engineers and FEA analysts working on
welding process simulations.

Step 1: Abaqus Model Setup

Prepare the base model in Abaqus/CAE for a realistic welding simulation.

• Create a 3D deformable flat plate and define a separate weld bead section.
• Assign material properties such as density, conductivity, specific heat, and plasticity.
• Use C3D8T elements for coupled thermal-mechanical analysis and finer mesh near the weld zone.

Step 2: Implementing the Birth and Death Method

Abaqus does not directly support element birth and death, but you can activate or deactivate regions
using *Model Change commands.

• Deactivate weld elements initially with *Model Change, Remove.
• Activate elements step-by-step using *Model Change, Add.

Step 3: Defining the Welding Heat Source (DEFLUX Subroutine)

Use a Fortran DEFLUX subroutine to define a moving Gaussian heat flux
that travels along the weld line. Below is an example structure:

SUBROUTINE DEFLUX(FILM,COORDS,JTEMP,TEMP,TIME,DTIME,NOEL,NPT,LAYER,KSPT)
  INCLUDE 'ABA_PARAM.INC'
  DOUBLE PRECISION FILM, COORDS(3), TEMP, TIME(2), DTIME
  INTEGER NOEL, NPT, LAYER, KSPT, JTEMP
  
  DOUBLE PRECISION Q, r, eta, V, A, r_max, x0
  PARAMETER (Q=3000.0, eta=0.8, V=5.0, A=6.0)
  
  x0 = V * TIME(1)
  r = SQRT((COORDS(1)-x0)**2 + COORDS(2)**2)
  r_max = 3.0
  IF (r .LE. r_max) THEN
     FILM = eta * Q * EXP(-3.0*(r**2)/(A**2))
  ELSE
     FILM = 0.0
  ENDIF
RETURN
END
  

Step 4: Analysis Steps and Element Activation

Create sequential steps for heat input, cooling, and residual stress analysis.

** Step 1: Heat input
*HEAT TRANSFER, STEADY STATE
1.0, 100.0
*MODEL CHANGE, ADD
Weld_Pass1
  

Step 5: Running the Simulation

1. Save and verify the model.
2. Compile the DEFLUX subroutine using the Abaqus command line.
3. Run: abaqus job=welding user=deflux.for

Step 6: Post-Processing and Results

• Visualize temperature distribution and thermal cycles.
• Check weld bead activation and residual stress fields.

This Abaqus welding tutorial demonstrates how to combine
element activation techniques and heat flux subroutines
for accurate FEA welding simulation.