# Structural Optimization of Combine Harvester Plate-Shell Undergoing Multi-Source Excitation
## 3 Results and Discussion
### Parameters of Enhanced Reinforcement  
There are many rotating parts on the combine harvester, and most relating parts are installed on the body frame. In the threshing machine part, such as the grain auger, the rotation axis is located in the middle of the plate. When considering the mechanical strength, reinforcing ribs are usually added to this kind of plate and shell to increase stability. From the perspective of dynamic response, the stiffener can also effectively increase the natural vibration frequency of the thin rectangular plate and also effectively suppress the vibration response of the plate to the concentrated simple harmonic force.  
In this section, the concentrated harmonic force is applied at two points on the center line of the 500 mm (500 mm \(\times\) 800 mm, 2 mm thick), located at 300 mm and 500 mm,respectively, with the amplitude of 100 N and 0 phase, on which the dynamic response of the variable distance, variable width, and variable thickness stiffeners is studied. The research shows that when the distance between the reinforced plate and the excitation point changes, it can be seen from Figure 8 that the farther the stiffeners are from the action point of the excitation force (100 mm/150 mm/200 mm), the greater the forced vibration response of the four-side solid support plate to the two-point excitation. This indicates that the closer the stiffener is to the excitation point, the better it suppresses the vibration.  
Further, for the four-side clamped plate, only the thickness of the stiffener is controlled, and the forced vibration response of the whole plate to the multi-source excitation is studied. As shown in Figure 9, with the gradual increase in the thickness of stiffeners (2 mm/3 mm/4 mm/5 mm), the forced vibration amplitude of the four-side fixed support plate under the two-point excitation gradually decreases. This shows that the multi-point excitation vibration response of the four-side clamped plate can be effectively controlled by increasing the thickness of the stiffener.  
Finally, for the four-side clamped plate, only the width of the stiffener is controlled, and the vibration response of the entire plate to the multi-source excitation is studied. As shown in Figure 10, with the width of the stiffeners gradually decreasing (50 mm/40 mm/30 mm/20 mm), the forced vibration amplitude of the four-side solid support plate under the two-point excitation gradually increases. As shown in Figure 10d, when the width of the stiffener is 20 mm, the forced vibration area of the four-side solid support plate extends from the excitation point side to the unapplied incentive point side, resulting in a large increase in the amplitude of the overall plate. This shows that the multi-point excitation vibration response of the four-sided simple support plate can be effectively controlled by increasing the width of the stiffener. When the width of stiffener is less than a certain degree, the inhibitory effect of reinforcement on the vibration response of plate surface also almost disappears.  
Figure 8: Response diagram of stiffened plate with variable distance. (**a**) Located at 100 mm. (**b**) Located at 150 mm. (**c**) Located at 200 mm.  
Figure 9: Response diagram of stiffened plate with variable thickness. (**a**) 2 mm thickness. (**b**) 3 mm thickness. (**c**) 4 mm thickness. (**d**) 5 mm thickness.