Go directly to procedural steps.
This step requires you to think about your simulation's end goals. What do you want to investigate? And specifically, what data do you want to see from the transient thermal portion of an LPBF Thermal-Structural simulation? Thermal analysis settings enable the customization of various options during the transient thermal solution, including identifying which items to solve for.
The transient thermal analysis will determine the temperature history during the build process. These temperatures will then be used in a static structural analysis to determine the build distortions and stresses. The Mechanical application will automatically determine all the steps and times needed for time integration in the simulation.
Options to consider include:
Hotspot – A significant cause of issues in additive manufacturing can be attributed to overheating during the build. This typically occurs when there are changes in cross sectional area and there is not enough material to pull heat away from a certain region. Overheating can lead to poorly shaped melt pools, affecting the part's material characteristics and porosity. You can check for the overheating issue with simulation by checking the temperature that each layer cools down to before a new layer is added. Add an LPBF Hotspot result item to your project so that the appropriate data is written out during solution. The LPBF Hotspot result tool configures the Export Layer End Temperature option so that the temperature of a layer just before a new layer is applied is written out to a file.
Layers to Build – An option is available to limit the number of layers to build in the simulation, that is, to simulate only a partial build process. This may be useful if you want to examine results in the lower portion of the build if you suspect there will be cracks or blade interference there.
Other Output Controls – For an AM Process Simulation, your results file will grow in size very quickly, so we recommend you keep the default output control settings that will suppress calculation of thermal flux, nodal forces, Euler angles, volume and energy, and other miscellaneous items. Nodal temperatures are stored at all time points by default but you can change that option so that temperatures are stored at the last heating and cooling steps only, or every N number of finite element layers.
Procedural Steps
Usually it is appropriate to leave most analysis settings set to "program-controlled." These settings are determined when you insert the AM Process object into the project tree. There are a couple of settings to note related to an AM Process Simulation, as described below.
To solve for hotspots, use the LPBF Hotspot tool in the LPBF Process Add-on.
Load the LPBF Process Add-on if you have not already done so. From the LPBF Process tab, click the LPBF Hotspot button. A new result object, called AM Hotspot, is added in the project tree under Solution in the Transient Thermal environment. (Alternatively, you can right-click Solution and select Insert > AM Hotspot.)
The LPBF Hotspot result tool automatically sets the Export Layer End Temperature option to Yes in the Analysis Settings object under Output Controls. It will write out to a file the temperature of a layer just before a new layer is applied. Node numbers and x, y, z locations are also written. The output is not written to the results file but rather to a tab-delimited file called AMResults.txt.
If you want to limit the number of layers to build in the simulation, select the Analysis Settings object under the Transient Thermal object and in Details, Additive Manufacturing Controls, change the Layers to Build to your desired value. Your results file will show results from the beginning layer only through the specified layer. (Hint: If you change the value of Layers to Build and you want to set it back to All, enter 0.) Pay attention to the active step as indicated at the top of the Details panel under Step Controls. The number of Layers to Build in the Cooldown Step will always equal the number of Layers to Build in the Build Step.
In Details of Analysis Settings, review the Output Controls and adjust them according to your needs.
To change the option of when to store element results for the Build Step, select Store Results At and choose All Time Points, Last Heating and Cooling Steps, or Every N Layers. (Layers refers to finite element layers, not powder deposition layers.)