Create the Annealing Step

Anneal the bridge part to relieve stresses and strains due to the localized heating and cooling of the manufacturing process.

The annealing procedure simulates the relaxation of stresses and plastic strains that occurs as metals are heated to high temperatures. Physically, annealing is the process of heating a metal part to a high temperature to allow the microstructures to recrystallize, removing dislocations caused by cold working of the material.

In practice, parts cool to ambient temperature and are removed from the additive manufacturing machine. Then, the supports and build tray are removed, and the completed parts are moved to an annealing oven. The cooling cycle is not simulated because it typically has little impact on the part.

In this example, you anneal the newly printed bridge part at 900oC for 11 hours to allow the microstructures to recrystallize and to lower the residual stress.

This task shows you how to:

Create the Static Step

Create a static step for the annealing process.

  1. From the Procedures section of the action bar, click Static Step .
  2. Name the static step Static Step_Annealing.
  3. Enter a step time of 11h.

    Note: The 3DEXPERIENCE platform automatically converts units, so 11h is converted to 39600s.

  4. Enter an initial time increment of 2000s and a maximum time increment of 3600s.
  5. Click OK.

Create the Tabular Amplitude

Create an amplitude to define the temperature throughout the annealing step, starting and ending at ambient temperature.

Amplitudes represent scale factors that allow arbitrary time (or frequency) variations of temperature, load, displacement, and other prescribed variables throughout a step. You can assign arbitrary schemes to vary the amplitude throughout a step.

A tabular amplitude curve is defined by a table of values at convenient points on a time scale.

In addition to time, frequency, and magnitude information, you can specify a smoothing factor in which the linear time variation is replaced by a smooth quadratic time variation. The scale factor you specify is then multiplied by the value of the feature (for our example, the magnitude of a temperature, which changes over the given time period).

Time points in the amplitude table correspond to step time points in the step in which the amplitude is applied. Any time points in the amplitude that are larger than the step duration are ignored during the simulation.

The amplitude defined here starts at a scale factor of 1 (300K) at time 0, changes to 3 (900K) through 10,000 and 30,000 seconds, and returns to 300K at 39,600 seconds. We define the temperature in the next task, Create the Prescribed Temperature.

  1. From the Setup section of the action bar, click Tabular Amplitude .
  2. Name the tabular amplitude Amp.1.
  3. Enter the Time/Frequency and Amplitude values (0, 1), (10000, 3), (30000, 3), and (39600, 1).
  4. Click OK.
    The amplitude appears in the Structural Analysis Case.1 > Amplitudes category of the tree.

Create the Prescribed Temperature

Create a prescribed temperature that constrains the assembly to have a specified temperature value throughout the simulation.

In this example, the prescribed temperature and the amplitude created in the previous task define the temperature for simulating the annealing process.

  1. From the Thermal section of the action bar, click Prescribed Temperature .
  2. Enter a temperature of 300Kdeg.
  3. Select Amp.1 as the amplitude.
  4. Click OK.
    The prescribed temperature appears in the Structural Analysis Case.1 > Predefined Fields category of the tree.

Create the Fixed Displacement

Apply a fixed displacement to constrain the build tray so that it cannot move during the simulation. Create a restraint on the previously created X, Y, and Z node groups to prevent motion during the annealing step.

  1. From the Restraints section of the action bar, click Fixed Displacement .
  2. Name the fixed displacement Fixed_Displacement_X.
  3. From the Support options, select Group as the selection method.
  4. From the selection tree, select X from the Model > FEM_AM > Groups category, and click OK.
  5. Constrain the translation in the X-direction, and click OK.
  6. Similarly, create Fixed_Displacement_Y and Fixed_Displacement_Z, with groups Y and Z, respectively, as the supports.
    Translation is now constrained in the Y-direction and Z-direction.
  7. From the tree, right-click Structural Analysis Case.1 > Static Step_Annealing > Clamp.1, and click Remove Clamp.1 in Static Step_Annealing.

    Removing the clamp from the bridge part allows it to relax during the annealing process since the only constraint is its attachment to the tray.

  8. Similarly, remove Prescribed Temperature.1 from Static Step_Annealing.

    The prescribed temperature from the build process is no longer needed.