# Structural Optimization of Combine Harvester Plate-Shell Undergoing Multi-Source Excitation
## 3 Results and Discussion
### Test Verification  
In order to verify the accuracy of the structural optimization method studied in this paper, the optimized plate is processed on the basis of the above optimization simulation. Figure 18 is the outline view of the panel before and after optimization. The original plate and the optimized plate are dynamically tested from the fundamental frequency of the restrained mode and the vibration response under multi-point vibration, so as to verify the optimization results. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Candidate Point 1** & **Candidate Point 2** & **Candidate Point 3** \\ \hline Width of Edge/mm & 10.837 & 10.436 & 10.215 \\ Width of Stiffener/mm & 7.0781 & 12.124 & 7.0952 \\ Thickness of foundation & 1.4139 & 1.3558 & 1.4117 \\ plate/mm & 8.6894 & 8.7348 & 8.657 \\ First natural frequency/Hz & 94.164 & 91.981 & 93.818 \\ Dynamic response/mm & 0.30028 & 0.23176 & 0.4407 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Candidate points of structural optimization. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Initial Value** & **Optimized Value** & **Correction Amount** \\ \hline Width of Edge/mm & 8 & 10 & +25\% \\ Width of Stiffener/mm & 25 & 7 & \(-72\%\) \\ Thickness of foundation & 1.2 & 1.4 & +16.7 \\ plate/mm & 8.7596 & 8.657 & \(-1.2\%\) \\ First natural frequency/Hz & 85.591 & 93.818 & +9.6\% \\ Dynamic response/mm & 1.1735 & 0.4407 & \(-62.4\%\) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Results of structural optimization. The position of the exciter refers to the position of the concentrated force on the combine harvester, where the grain conveying auger and the miscellaneous auger are located. Referring to the simulation results (Figure 19), the vibration displacement is collected at the place where the amplitude of the plate and shell is large. There are four measurement points, marked as A, B, C, and D.  
By adjusting the rotational speed of the exciter, the exciting force on the plate shell can reach 1000 N. Under the action of two concentrated harmonic forces, the displacement responses of the original plate and the optimized plate at points A, B, C, and D are shown in Figure 20.  
It can be seen from Figures 21 and 22 that the two plates before and after optimization have larger vibration responses at points B and D near the exciter, while point C between the two excitation sources is the place with the largest vibration response, which may be  
Figure 19: Diagram of simulation dynamic response. Figure 20: Test layout. Figure 18: Comparison of panels before and after optimization. due to that point C is located at the superposition of the two vibrations. Comparing the data of the above two panels before and after optimization, the amplitude of vibration response of the optimized panel is smaller than that of the panel before optimization at all four points. This shows that the optimized plate-shell structure effectively reduces the vibration response under the reuse of two-point concentrated harmonic force. Figure 21: Vibration response of the original shell. Figure 22: Vibration response of the optimized plate. In addition, it is necessary to verify whether the fundamental frequency of the optimized plate-shell structure is improved. Therefore, in this paper, constrained modal tests are carried out on the original plate and the optimized plate, and the fundamental frequencies of the two plates before and after optimization are obtained through the test. The test results of the two plate-shell structures obtained are shown in the Table 6.  
It can be seen from the table that the first-order natural frequency of the optimized plate-shell structure has increased by 14.6%, from 88.08 to 100.95, avoiding the resonance range of the main components on the combine harvester. At the same time, the fundamental frequencies of other orders have also been greatly improved. It is also close to the simulation results.