# Finite Element Analysis of Thermal Stress and Thermal Deformation in Typical Part during SLM
## 3 Simulation Process and Operation
### Simulation Runs  
The original 3D model of the component was designed as presented in Figure 2(a). It included a panel with a relatively flat surface, a water-cooling channel, an internal connection with the water nozzle as well as many external cooling fins on the plate. Based on the above thermal-mechanical algorithm and software platform simulation, the simulation produced a diagram, layer-by-layer, as presented in Figure 2(b). This diagram contained a 3 mm support, and certain points were marked on the graph.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameters** & **Simulation** & **Experiment** \\ \hline Laser power & 100 W & 100 W \\ Scan speed & 500 mm/s & 500 mm/S \\ Thickness & 0.03 mm & 0.03 mm \\ Laser absorptivity & 0.7 & 0.7 \\ Substrate Temperature & 20 \({}^{\circ}\)C & 20 \({}^{\circ}\)C \\ Materials & 316L powder & 316L powder \\ Equipment & — & Concept \\ \hline \hline \end{tabular}
\end{table}
Table 2: Simulation process parameters and laser energy values.  
Figure 3: Chart of simulation model. (**a**) 3D Model; (**b**) the forming model.  
Figure 2: Simulation development flow chart.  
Subsequent to the finite element thermal-mechanical coupling solution, the stress nephograms of several forming stages are presented in Figure 4. Following laser melting, the melt solidification was achieved, while thermal stress regions were macroscopically generated for different temperature gradients as the cooling progressed. The reason for stress occurrence was that different molecular motion rates under different temperature gradients can cause different orientations and spacing of the crystals, resulting in stress formation with the slowest heat transfer point at the center, along with tension at the side and pressure in the center. Through the effective stress cloud diagram, it was observed that the plane stress was evenly distributed throughout the material. Furthermore, the four stages of the effective stress nephogram and its ruler are demonstrated in Figure 4a-d. From the first to the fourth stage, the stress value gradually increased, and the layer-by-layer cyclical superposition effect of the thermal stress from the base layer to the upper layer was produced as a result. This could be obtained because the lower layer was continuously heated and cooled by the upper layer. Following the formation of several hundred layers, the normal stress distribution of the model could be observed at the fourth stage. The stress value of the support part exceeded the solid stress value of the part from the cloud image color distribution. In addition, it can be observed in Figure 4e that the stress was reduced after the substrate was removed. Furthermore, this stress, following the thermal stress release, occurred as residual stress. Specifically, the existence of the above stresses would inevitably lead to strain generation and macroscopic thermal deformation. The simulation results are thoroughly analyzed in Section 4.  
Figure 4: Phase results of simulation. (**a**) First stage—support formation; (**b**) second stage—water cooling channel formation; (**c**) third stage—nozzle formation; (**d**) fourth stage—formation of the entire part; (**e**) fifth stage—support removal.