# CNN-Based Ti-6242 Impeller Forging Process Design for Uniform Strain Distribution
## 4 Result and Discussion
### Validation of Improved Forging Process Design Method  
To verify the effectiveness of the suggested method, a comparison was made with Method I and II. Firstly, the comparison was conducted using Target impeller I geometry. The initial billet was upset using the appropriate upsetting stroke derived from Section 3.2, followed by preform forging and final forging to obtain the target impeller as demonstrated in Figure 9a. The two-step forging results using Method I and Method II are shown in Figure 8b,c, respectively. It was found that the proposed method produced a more uniform strain distribution in the target impeller, as evidenced by a 17.5% reduction in mean strain, a 46.4% reduction in strain standard deviation, and a 59.7% reduction in maximum strain compared to Method I. Compared to Method II, the proposed method showed a 0.8% reduction in mean strain, a 52.5% reduction in strain standard deviation, and a 54.9% reduction in maximum strain. Subsequently, the forging results were compared using Target impeller II geometry. When the appropriate upsetting stroke of 100 mm was used to derive the forging results, the forging of the target impeller using the method proposed in this study is shown in Figure 10a. The results of the two-step forging are shown in Figure 10b when Method I was used, and Figure 10c when Method II was used. When the proposed method was used for forging, it was confirmed that the average strain rate of the target impeller decreased by 15.2% and the standard deviation of strain rate decreased by 45.7% compared to Method I. In addition, the maximum strain rate was also confirmed to have decreased by 40.7%. When the proposed method was compared with Method II, the average strain rate decreased by 18.4%, the standard deviation of the strain rate decreased by 44.1%, and the maximum strain rate decreased by 27.6%. Figure 8: Variation of effective strain average and standard deviation for case of impeller shapes studied in: (**a**) Target impeller I; (**b**) Target impeller II; (**c**) Target impeller III. In all three cases, forging using the upsetting stroke suggested by the design guideline yielded in the lowest average strain and standard deviation. Finally, the forging results were compared using the geometry of Target impeller III. When using the same method as in the previous cases, the forging results after 90 mm upsetting using the proposed method in this study for the target impeller are shown in Figure 11a. The forging results are shown in two steps in Figure 11b when using Method I and Figure 11c when using Method II. When the proposed method was used for forging, it was found that the mean strain decreased by 38.6% and the strain's standard deviation decreased by 48.9% compared to Method I. It was also confirmed that the maximum strain decreased by 45.7%. When the proposed method was compared with Method II, the mean strain decreased by 29.5%, the strain's standard deviation decreased by 48.9%, and the maximum strain decreased by 35.3%. In all three impeller designs, it was observed that the proposed design method in this study reduced the maximum strain, mean strain, and strain standard deviation, thereby alleviating strain concentration. As shown in Figure 12, the proposed forging process also reduced the strain range compared to Method I and II. However, the strain range still did not meet the required level of 1.2, as stipulated in previous studies [39, 40]. Therefore, to meet this requirement, it is necessary to reduce the maximum strain by decreasing it below the minimum strain value that does not result in significant changes in strain values for each method. Consequently, future model modifications should focus not only on achieving uniform strain distribution but also on reducing the maximum strain. Figure 10: Strain distribution result for Target impeller II forging following: (**a**) proposed method; (**b**) Method I; (**c**) Method II. Figure 9: Strain distribution result for Target impeller I forging following: (**a**) proposed method; (**b**) Method I; (**c**) Method II.