# 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  
The [PERSON] bending stress theory was used to estimate face width range of the picking device gear sets for AISI 1060 steel and SCM 420H carbon steel materials. The allowable stress of the materials and operating conditions were considered to select the range of face widths as the thickness of the gear sets. Table 6 shows the face width range for different materials and operating speeds. For the allowable stress of AISI 1060 steel (high carbon steel) and SCM 420H carbon steel (medium carbon steel), the face width range of the gear set was found to be between 3 and 5 mm. Therefore, 3 and 5 mm face widths were considered for further stress analysis of the material of the picking device gear mechanism. Figure 8 shows the load (torque) of the picking device gear mechanism for four different operating speeds. The torque on the picking device showed regular fluctuation patterns during operation. The average torque at 9.425 rad/s was approximately two-times higher than that at 6.284 rad/s. The maximum torque was found when the picking mechanism changed direction from the y- to the x-axis. The maximum torque was found to be 3.65 Nm for the 9.425 rad/s operating condition. The average torque values for the picking device at 6.284, 7.331, 8.378, and 9.425 rad/s were 0.17 \(\pm\) 0.32, 0.26 \(\pm\) 0.33, 0.28 \(\pm\) 0.39, and 0.32 \(\pm\) 0.45 Nm, respectively. Therefore, the load on the picking device increased when the speed of the device increased, as expected. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Specification** \\ \hline \multirow{2}{*}{Electric motor} & Rated power, kW & 1.5 @ 366.52 rad/s \\  & Rated torque, Nm & 3.5 \\ \multirow{2}{*}{Operating speed, rad/s} & \multirow{2}{*}{6.284, 7.331, 8.378, and 9.425} \\  & & \\ \end{tabular}
\end{table} 
Table 5: Specifications of the stress and fatigue analysis experimental setup. Figure 7: Load measurement test bench for the picking device: (**a**) picking device, (**b**) torque sensor, (**c**) motor, (**d**) inverter, and (**e**) data storage panel. The roll angle \(\varphi_{C}\) was calculated as 0.20 and 0.16 rad for the crank and cam gear sets, respectively. That is, the contact starts from 0 rad and ends at 0.20 and 0.16 rad for the crank and cam gear sets, respectively. The torque load was applied to the center of each gear. The contact stress on the pinion at the contact location was observed for various roll angles. Table 7 shows the maximum contact stress for the crank gear set under different load conditions, where the roll angle increased from 0.02 to 0.18 rad in 10 equal increments. In the FEA, tip relief was not considered, and the maximum stress levels for the full load condition at the contact location were obtained as 890.96 (Case 4), 613.78 (Case 5), 885.06 (Case 4), and 695.02 MPa (Case 6) for 3 and 5 mm face widths of SCM 420H carbon steel and AISI 1060 steel, respectively. While the gear and pinion are meshed and revolved, the stress reaches a maximum around the contact point corresponding to one pair of contacting teeth, and then reduces. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{
\begin{tabular}{c} **Rotational** \\ **Speed, rad/s** \\ \end{tabular} } & \multicolumn{3}{c}{**Face Width, mm**} \\ \cline{2-5}  & \multicolumn{3}{c}{**AISI 1060 Steel**} & \multicolumn{3}{c}{**SCM 420H Carbon Steel**} \\ \cline{2-5}  & \multicolumn{1}{c}{**Crank Gear**} & \multicolumn{1}{c}{**Cam Gear**} & \multicolumn{1}{c}{**Crank Gear**} & \multicolumn{1}{c}{**Cam Gear**} \\ \hline
6.284 & 4.50 & 4.06 & 4.29 & 3.87 \\
7.331 & 4.56 & 4.10 & 4.36 & 3.92 \\
8.378 & 4.82 & 4.33 & 4.60 & 4.13 \\
9.425 & 5.45 & 4.88 & 5.20 & 4.65 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Determined picking device gear set face width based on the operating speed and material properties. Figure 8: Picking device gear mechanism torque based on the operating speed.