# Stress and Fatigue Analysis of Picking Device Gears for a 2.6 kW Automatic Pepper Transplanter
## 3 Results and Discussion
### Appropriate Gear Material and Face Width
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **Load** \\ **Type** \\ \end{tabular} } & \multirow{2}{*}{**Case**} & \multirow{2}{*}{\
\begin{tabular}{c} **Roll** \\ **Angle, rad** \\ \end{tabular} } & \multicolumn{3}{c}{**Crank Gear Set Maximum Stress, MPa**} \\ \cline{3-7}  & & & **SCM 420H Carbon Steel** & \multicolumn{3}{c}{**AISI 1060 Steel**} \\ \cline{3-7}  & & & **3 mm Face** & **5 mm Face** & **3 mm Face** & **5 mm Face** \\  & & & **Width** & **Width** & **Width** \\ \hline \hline \multirow{4}{*}{Half load} & 1 & 0.02 & 137.65 & 177.39 & 149.16 & 203.93 \\  & 2 & 0.04 & 808.64 & 451.56 & 853.08 & 523.30 \\  & 3 & 0.06 & 855.48 & 519.96 & 890.97 & 636.33 \\  & 4 & 0.08 & 890.96 & 576.07 & 885.06 & 671.71 \\ \cline{1-1}  & 5 & 0.10 & 804.97 & 613.78 & 837.69 & 665.92 \\ \cline{1-1}  & 6 & 0.12 & 631.63 & 597.10 & 700.32 & 695.02 \\ \cline{1-1}  & 7 & 0.14 & 496.23 & 498.34 & 518.65 & 562.09 \\ \cline{1-1}  & 8 & 0.16 & 318.29 & 321.68 & 335.30 & 410.71 \\ \cline{1-1}  & 9 & 0.18 & 228.34 & 262.58 & 242.62 & 278.18 \\ \cline{1-1}  & 10 & 0.20 & 128.21 & 143.05 & 137.61 & 168.09 \\ \cline{1-1} Full load &
\begin{tabular}{c} AGMA \\ (6.284 rad/s) \\ \end{tabular} & & 724.22 & 560.98 & 731.12 & 566.32 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Maximum stress obtained through contact stress analysis for the crank gear set. Table 8 shows the maximum contact stress for the cam gear set under different load conditions. The roll angle was increased from 0.01 to 0.15 rad in 10 equal increments. For the 3 and 5 mm face widths, the contact stress levels that the cam gear set were calculated as 620.63 and 480.74 and 626.54 and 485.31 MPa for SCM 420H carbon steel and AISI 1060 steel material, respectively. In the stress analysis using FEA, the contact stresses were 769.05 (Case 4), 567.04 (Case 5), 786.35 (Case 4), and 607.67 MPa (Case 6) for 3 and 5 mm face widths of SCM 420H carbon steel and AISI 1060 steel, respectively. From the stress analysis, the stresses in Cases 0 to 3 and 8 to 10 were not considered because they generated a drastic load (half load). In the full-load cases (4 to 7), the stress propagated diagonally and generated a maximum stress at the contact point. Cases 5 and 6 corresponded to the best-suited conditions among the full-load cases because they maintained the middle portion of the roll angle and applied stress more uniformly [16]. Based on the results, the SCM 420H carbon steel material showed the maximum stress in Cases 5 and 6. From the comparison of FEA and AGMA theory contact stress, the highest error was found for a 3 mm face width for both materials. However, the lowest error was for the 5 mm face width of SCM 420H carbon steel. Therefore, a 5 mm face width of SCM 420H carbon steel was selected for the crank gear set to operate the picking mechanism. Similarly, for the cam gear analysis, the highest error was found for the 3 mm face in both materials. However, the lowest error was calculated for the 5 mm face width SCM 420H carbon steel. For the cam gear set, a 5 mm face width SCM 420H carbon steel would be suitable as the material for supporting the gear contact stress in field operation. Figure 9 shows the contact stress percentage error for the picking device gear mechanism.