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

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

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.

Path of a laser heat source.

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.

Goldak expression for energy 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.

For information on specifying free surface radiation and convective heat transfer, see Progressive Cooling via Convection and Radiation.