*2.6. Model Validation*

To verify the established FSW model, a validation simulation was conducted according to the previous experiment [33]. In the validation simulation, the size of workpiece, technological parameters, and material are the same as those in the referenced experiment. The accuracy of the established FSW model was studied by comparing with the actual heat cycle curve of the measurement points located 8 mm from the weld center under different welding speeds. Figure 4 shows the heat cycle curve of experiment and simulation. By comparing the results between simulation and experiment, it can be seen that the heat cycle curves obtained by this model are basically consistent with those obtained by the actual welding test. Therefore, this model is accurate and feasible.

**Figure 4.** Comparison results of thermal cycling curves at different welding speeds obtained by simulation and experiment.

#### **3. Results and Discussions**
