## 3 Results and Discussion  
### Experimental Results  
The surfaces of AISI 8620, AISI 5140, AISI 4140, and AISI 1020 materials were subjected to shot SP and VSP processes using a variety of process parameters in the current study. After the process, the surface roughness values of the samples were evaluated, and the outcomes are displayed in Table 5.  
Among the samples in the AISI 8620 sample group to which the SP process was applied, the highest roughness value was obtained at 12-14 A intensity. Compared to the traditional SP procedure, it was discovered that the vibratory SP methodology produced reduced surface roughness values in AISI 8620 samples. The group with the greatest surface roughness rating was the VSP procedure, which took 30 min to complete and used a 4 mm ball diameter. When the ball diameter is fixed, the surface roughness increases with decreases in processing \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Applied Process** & **Process Parameter** & **Surface Roughness (Ra) (\(\mu\)m)** & **Material** \\ \hline SP & Non-treated & 1.34 & AISI 8620 \\  & 12–14 A & 6.27 & \\  & 18–20 A & 4.6 & \\  & 24–26 A & 4.45 & \\ \hline VSP & 30 s \(-\)2 mm & 2.13 & \\  & 60 s \(-\)2 mm & 1.92 & \\  & 30 s \(-\)4 mm & 2.50 & \\  & 60 s \(-\)4 mm & 2.30 & \\ \hline SP & Non-treated & 1.98 & AISI 5140 \\  & 12–14 A & 3.16 & \\  & 18–20 A & 5.23 & \\  & 24–26 A & 5.21 & \\ \hline VSP & 30 s \(-\)2 mm & 2.30 & \\  & 60 s \(-\)2 mm & 1.90 & \\  & 30 s \(-\)4 mm & 2.70 & \\  & 60 s \(-\)4 mm & 2.30 & \\ \hline SP & Non-treated & 1.70 & AISI 4140 \\  & 12–14 A & 4.30 & \\  & 18–20 A & 4.70 & \\  & 24–26 A & 4.40 & \\ \hline VSP & 30 s \(-\)2 mm & 2.70 & \\  & 60 s \(-\)2 mm & 2.40 & \\  & 30 s \(-\)4 mm & 2.90 & \\  & 60 s \(-\)4 mm & 2.60 & \\ \hline SP & Non-treated & 1.50 & AISI 1020 \\  & 12–14 A & 4.80 & \\  & 18–20 A & 5.20 & \\  & 24–26 A & 5.10 & \\ \hline VSP & 30 s \(-\)2 mm & 2.25 & \\  & 60 s \(-\)2 mm & 2.30 & \\  & 30 s \(-\)4 mm & 2.70 & \\  & 60 s \(-\)4 mm & 2.50 & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Surface roughness values of samples with SP processes at different process parameters. time, but the roughness value increases when the ball diameter grows concurrently with the processing time. The increase in the ball diameter in the SP process causes the process to have a greater effect on the surface of the part. Similarly to those obtained from the AISI 4140 material, the roughness values obtained from the AISI 5140 material using the traditional SP process were maximum at the 18-20 A Almen intensity. As the Almen intensity was increased to 24-26 A, surface roughness increased as well. Because of the VSP method's nature, surface roughness values decreased compared to traditional SP methods. When the surface roughness values of AISI 4140 samples were examined, the samples pened at 18-20 A in the traditional SP technique yielded the highest values, whereas the samples pened at 24-26 A intensity levels had lower values. Other balls with high Almen intensity struck the surface hills of the material between the pits, bringing down their height and leveling their surfaces. When a traditional SP process was applied to AISI 1020 steel, an increase in surface roughness values occurred as the Almen peening intensity increased. Conversely, in the VSP samples, the samples with small-diameter balls had lower degrees of roughness than the samples with high ball diameters. As was the case with the AISI 8620 material, the samples shot-pened using the vibratory approach had rougher values than those shot-pened using the traditional method. The effect of the SP process on hardness was determined by measuring the hardness from the surface to the center. The outcomes are displayed in Figure 2. When comparing the samples that underwent SP to those that did not, a noteworthy improvement in hardness values was observed. At 24-26 A Almen intensity, a value of 251 Vickers was recorded for the greatest hardness value of AISI 8620 material.