Go directly to procedural steps.
In this step, think about your end goals for the simulation and what data you want to see written out from the structural portion of the simulation. Structural analysis settings allow for the customization of various options during the static structural solution, including identifying which items to solve for.
Options to consider include:
Recoater Interference – A significant concern in additive manufacturing is whether the build will print successfully without experiencing recoater interference (sometimes called blade crash). This phenomenon occurs when the powder recoater blade hits into a portion of the built part that has deformed extensively because of residual stresses. Usually the result is a stopped process and a failed build. If checking for recoater interference is a simulation goal, add an LPBF Recoater Interference result now to your project so that the appropriate data is written out during solution. The LPBF Recoater Interference result tool configures the Export Recoater Interference output control option so that the Z-deformation of a layer just before applying a new layer is written out to a file.
High Strain – When the strain in a part exceeds the elongation a material can withstand, a failure can occur resulting in cracking throughout the part or supports. The LPBF High Strain result tool allows you to identify regions of the part that may be prone to forming cracks during or after the build process by highlighting critical strain values. The LPBF High Strain result tool configures the Export High Strain output control option so that the maximum equivalent strain experienced during the build process is written out to a file.
Reference Temperature – The Reference Temperature is the temperature at which thermal strains do not exist in a material. In the simulation of the AM process, our assumption is that each finite element super layer is added (with the element birth/death technique) at the melting temperature for the material and is initially strain-free. (We set Tref = Tmelt by default.) As the build cools, thermal strains develop. The static structural analysis will use the temperature results of the transient thermal analysis to compute the displacements, stresses, strains, and forces due to these induced thermal strains.
Relaxation Temperature – If you will be simulating a heat treatment process such as annealing after the build, you will probably want to specify a Relaxation Temperature. Lower than the melting temperature, the relaxation temperature is the temperature at which strains begin to soften. (Using a creep model in Engineering Data is an alternative stress relaxation mechanism.) Refer to the advanced topic Simulating Heat Treatment after the Build for details.
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. The number specified here must not be more than the number of layers to build used in the thermal analysis step if you are performing a thermal-structural simulation.
Other Output Controls – Your structural results file will grow in size very quickly, so we recommend you keep the default output control settings that will suppress calculation of contact data, nodal forces, Euler angles, volume and energy, and other miscellaneous items. Consider suppressing the calculation of stresses and strains if you are only interested in distortion, as these data, in particular, will easily increase the size of the results file and it may become unmanageable. Additional controls allow you to specify when to store results for the build step: for all layers, for the last heating and cooling steps, or every N layers.
Procedural Steps
As with the thermal analysis, many analysis settings in the structural analysis are program controlled.
To solve for recoater interference, use the LPBF Recoater Interference 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 Recoater Interference button. A new result object, called LPBF Recoater Interference, is added in the project tree under Solution in the Static Structural environment. (Alternatively, you can right-click Solution and select Insert > LPBF Recoater Interference.)
The LPBF Recoater Interference result tool automatically sets the Export Recoater Interference option to Yes in the Analysis Settings object under Output Controls. It will write out to a file the z-deformation 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.
To solve for high strain areas, use the LPBF High Strain 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 High Strain button. A new result object, called LPBF High Strain, is added in the project tree under Solution in the Static Structural environment. (Alternatively, you can right-click Solution and select Insert > LPBF High Strain.)
The LPBF High Strain result tool automatically sets the Export High Strain option to Yes in the Analysis Settings object under Output Controls. It will write out to a file the maximum equivalent strain experienced during the build process. 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 AMHighStrain.txt.
Select the Analysis Settings object under the Static Structural object and in Details, note the Additive Manufacturing Controls. The Reference Temperature is automatically set to the material's melting temperature. (You can see this value in Engineering Data for your chosen material.)
If you added a Heat Treatment Step in the AM Process Sequence worksheet, you will probably want to specify a Relaxation Temperature. Under Additive Manufacturing Controls, change the Relaxation Temperature to User Specified and change the Value to the appropriate temperature. For additional steps to complete the Heat Treatment Step, see the advanced topic Simulating Heat Treatment after the Build.
To limit the number of layers to build in the simulation, under Additive Manufacturing Controls change the Layers to Build to your desired value. The number specified must not be more than the number of layers to build used in the thermal analysis if you are performing a thermal-structural simulation.
Review the Output Controls and suppress items not of interest.
Turn off calculations of Stress and Strain by changing those options from Yes to No. (Hint: Simply double-clicking in the Yes box changes it to No.)
To change the option of when to store results, select Store Results At and choose All Layers, Last Heating and Cooling Steps, or Every N Layers.