Thermomechanical Analysis of Powder Bed–Type Additive Manufacturing Processes Using the Trajectory-Based Method

Special-purpose techniques and user subroutines are available to define the relevant process parameters for material deposition and heat sources. These internal built-in user subroutines are accessed by starting names and types with "ABQ_" as described below.

This page discusses:

See Also
Progressive Element Activation
In Other Guides
Sequential thermomechanical analysis of a laser powder bed fusion build
Heat energy balance
Defining Moving or Stationary Nonuniform Heat Flux in User Subroutine UMDFLUX
*EVENT SERIES
*EVENT SERIES TYPE
*TABLE COLLECTION
*PARAMETER TABLE
*PARAMETER TABLE TYPE
*PROPERTY TABLE
*PROPERTY TABLE TYPE

ProductsAbaqus/Standard

In a powder bed–type additive manufacturing (AM) process, such as selective laser sintering (SLS) and stereolithography (SLA), a recoater or a roller blade deposits a single layer of raw material. Then, a high-powered laser scans a single cross-section of the part over the layer of raw material to fuse it with the previously laid layer underneath (see Figure 1). The layer-upon-layer raw material deposition is simulated by progressive element activation in a structural or a thermal analysis, and the laser-induced heating is simulated by a moving heat flux in a thermal analysis.

Figure 1. Recoater or roller blade motion in a powder bed–type AM process.

Specifying Progressive Element Activation

The layer-by-layer deposition of raw material from a recoater or roller blade is simulated using progressive element activation in a structural or a thermal analysis. The following steps are required to define the deposition process completely:

  • Define the motion of the center point of the recoater in an event series following the convention for infinite line toolpath-mesh intersection (see Infinite Line Toolpath-Mesh Intersection).
  • Create a table collection with a name that begins with "ABQ_AM". The table collection must contain a parameter table of type "ABQ_AM_MaterialDeposition".
  • In the parameter table, include a reference to the event series for the material deposition, and set the deposition process type to "Roller".
  • Refer to the table collection in the progressive element activation.

Abaqus activates elements automatically according to the specified material deposition sequence.

A dedicated collection of parameter table, property table, and event series types is available to include all of the definitions required by special-purpose techniques for additive manufacturing. You can use the abaqus fetch utility to obtain the file containing all of the type definitions of parameter tables, property tables, and event series required by the special-purpose techniques for additive manufacturing as follows:

abaqus fetch job=ABQ_am_special_purpose_types.inp

Input File Usage

Use the following options to define progressive element activation in a thermal or a structural analysis:

EVENT SERIES, NAME=event series name, TYPE=ABQ_AM_MaterialDeposition

              
                
                  
                    t
                  
                  
                    1
                  
                
                ,
                
                  
                    x
                  
                  
                    1
                  
                
                ,
                
                  
                    y
                  
                  
                    1
                  
                
                ,
                
                  
                    z
                  
                  
                    1
                  
                
                ,
                1
              
            

              
                
                  
                    t
                  
                  
                    2
                  
                
                ,
                
                  
                    x
                  
                  
                    2
                  
                
                ,
                
                  
                    y
                  
                  
                    2
                  
                
                ,
                
                  
                    z
                  
                  
                    2
                  
                
                ,
                0
              
            

              
                
                  
                    t
                  
                  
                    3
                  
                
                ,
                
                  
                    x
                  
                  
                    3
                  
                
                ,
                
                  
                    y
                  
                  
                    3
                  
                
                ,
                
                  
                    z
                  
                  
                    3
                  
                
                ,
                1
              
            

              
                
                  
                    t
                  
                  
                    4
                  
                
                ,
                
                  
                    x
                  
                  
                    4
                  
                
                ,
                
                  
                    y
                  
                  
                    4
                  
                
                ,
                
                  
                    z
                  
                  
                    4
                  
                
                ,
                0
              
            
...

              
                
                  
                    t
                  
                  
                    n
                  
                
                ,
                
                  
                    x
                  
                  
                    n
                  
                
                ,
                
                  
                    y
                  
                  
                    n
                  
                
                ,
                
                  
                    z
                  
                  
                    n
                  
                
                ,
                0
              
            
TABLE COLLECTION, NAME="ABQ_AM_table collection name"
PARAMETER TABLE, TYPE="ABQ_AM_MaterialDeposition"
event series name, "Roller"
PARAMETER TABLE, TYPE=ABQ_AM_MaterialDeposition_Advanced
"Full" or "Partial", min volume fraction threshold for partial activation, 
max volume fraction threshold for partial activation, volume fraction threshold for full activation
...
ELEMENT PROGRESSIVE ACTIVATION, NAME=activation name, ELSET=element set name
...
STEP
STATIC or HEAT TRANSFER
...
ACTIVATE ELEMENTS, ACTIVATION=activation name
 "ABQ_AM_table collection name"
...

Specifying a Concentrated Moving Heat Source

You can approximate the laser spot as a concentrated moving heat flux if the size of the finite elements used in a thermal analysis is significantly larger than the size of the laser spot (see Figure 2). The following steps are required to define the concentrated moving heat source completely:

  • Define the scanning trajectory and power of the laser in an event series following the convention for point toolpath-mesh intersection (see Point Toolpath-Mesh Intersection).
  • Create a table collection with a name that begins with "ABQ_AM". The table collection must contain a parameter table of type "ABQ_AM_MovingHeatSource".
  • In the parameter table, include a reference to the event series for the point heat source and set the heat source type to "Concentrated".
  • Refer to the table collection in the distributed load definition.

Abaqus computes and applies moving heat fluxes to each element automatically according to the specified scanning trajectory.

Figure 2. Path of a laser heat source.

Input File Usage

Use the following options to define a concentrated moving heat flux:

EVENT SERIES, NAME=event series name, TYPE="ABQ_AM_PowerMagnitude"
data lines to define the motion of the laser spot
TABLE COLLECTION, NAME="ABQ_AM_table collection name"
PARAMETER TABLE, TYPE="ABQ_AM_MovingHeatSource"
event series name, "Concentrated"
PROPERTY TABLE, TYPE="ABQ_AM_AbsorptionCoeff"
absorption coefficient
...
STEP
HEAT TRANSFER
...
DFLUX
element set name, MBFNU, ,"ABQ_AM_table collection name"
...

Specifying a Moving Heat Source with a Goldak Distribution

If the size of the finite elements used in a thermal analysis is comparable to the size of the laser spot, the laser power, Q, can be distributed over a volume based on the Goldak rule of laser energy distribution. Figure 3 shows the Goldak expression for energy distribution, q, from a laser source. The local x-axis indicates the laser motion direction defined by an event series segment. The following steps are required to define the moving heat source completely:

  • Define the trajectory of the laser spot in an event series similar to the definition of the concentrated moving heat source.
  • Create a table collection with a name that begins with "ABQ_AM". The table collection must contain a parameter table of type "ABQ_AM_MovingHeatSource" and a parameter table of type "ABQ_AM_MovingHeatSource_Goldak".
  • In the parameter table of type "ABQ_AM_MovingHeatSource" include a reference to the event series for the moving heat source and set the heat source type to "Goldak".
  • In the parameter table of type "ABQ_AM_MovingHeatSource_Goldak" define the parameters of the Goldak distribution (a, b, cf, cr, ff, and fr).
  • Refer to the table collection in the distributed load definition.

Abaqus computes and applies the moving distributed heat fluxes automatically according to the specified Goldak distribution and scanning trajectory.

Figure 3. Goldak expression for energy distribution.

Input File Usage

Use the following options to define a moving heat source with the Goldak distribution:

EVENT SERIES, NAME=event series name, TYPE="ABQ_AM_PowerMagnitude"
data lines to define the motion of the laser
TABLE COLLECTION, NAME="ABQ_AM_table collection name"
PARAMETER TABLE, TYPE="ABQ_AM_MovingHeatSource"
event series name, "Goldak"
PARAMETER TABLE, TYPE="ABQ_AM_MovingHeatSource_Goldak" 
# subdivisions in x-direction, # subdivisions in y-direction, # subdivisions in z-direction,

              
                a
              
            , 
              
                b
              
            , 
              
                
                  
                    c
                  
                  
                    f
                  
                
              
            , 
              
                
                  
                    c
                  
                  
                    r
                  
                
              
            , 

              
                
                  
                    f
                  
                  
                    f
                  
                
              
            , 
              
                
                  
                    f
                  
                  
                    r
                  
                
              
            , box size factor
PROPERTY TABLE, TYPE="ABQ_AM_AbsorptionCoeff"
absorption coefficient
...
STEP
HEAT TRANSFER
...
DFLUX
element set name, MBFNU, ,"ABQ_AM_table collection name"
...

Specifying a Moving Heat Source with a Uniform Distribution

If the size of the finite elements used in a thermal analysis is comparable to the size of the laser spot, the laser power can be distributed uniformly over a box-shaped volume. The following steps are required to define the moving heat source completely:

  • Define the trajectory of the laser spot in an event series similar to the definition of the concentrated moving heat source.
  • Create a table collection with a name that begins with "ABQ_AM". The table collection must contain a parameter table of type "ABQ_AM_MovingHeatSource" and a parameter table of type "ABQ_AM_MovingHeatSource_Uniform".
  • In the parameter table of type "ABQ_AM_MovingHeatSource", include a reference to the event series for the moving heat source, and set the heat source type to "Uniform".
  • In the parameter table of type "ABQ_AM_MovingHeatSource.Uniform", define the parameters of the box-shaped volume.
  • Refer to the table collection in the distributed load definition.

Abaqus computes and applies the moving distributed heat fluxes automatically.

Input File Usage

Use the following options to define a moving heat source with a uniform distribution:

EVENT SERIES, NAME=event series name, TYPE="ABQ_AM_PowerMagnitude"
data lines to define the motion of the laser
TABLE COLLECTION, NAME="ABQ_AM_table collection name"
PARAMETER TABLE, TYPE="ABQ_AM_MovingHeatSource"
event series name, "Uniform"
PARAMETER TABLE, TYPE="ABQ_AM_MovingHeatSource_Uniform" 
# subdivisions in x-direction, # subdivisions in y-direction, # subdivisions in z-direction, 
offset in x-direction, offset in y-direction, offset in z-direction,
box length in x-direction, box length in y-direction, box length in z-direction,
PROPERTY TABLE, TYPE="ABQ_AM_AbsorptionCoeff"
absorption coefficient
...
STEP
HEAT TRANSFER
...
DFLUX
element set name, MBFNU, ,"ABQ_AM_table collection name"
...