## 4 Results Analysis  
### Simulation Results Analysis  
As mentioned earlier, the rudder stock is welded from two materials, with the rudder stock head and joint made of 925A and the middle pull rod made of 20# steel. The density of 925A is 7.938 g/m\({}^{3}\), [PERSON]'s modulus is 2.13 \(\times\) 10\({}^{5}\), and the Poisson's ratio is 0.3. The density of 20# steel is 7.84 g/m\({}^{3}\), [PERSON]'s modulus is 2.06 \(\times\) 10\({}^{5}\), and the Poisson's ratio is 0.282. The mechanical performance parameters of the material are detailed in Table 1. After defining the material properties, the tetrahedron is used to divide the grid. To explore the convergence of finite element meshing, this paper refers to the computing power of the computer and sets a total of five unit sizes of 5 mm, 7.5 mm, 10 mm, 12.5 mm, and 15 mm for comparative experiments. According to the comparison results of the above five groups of unit sizes, it is finally confirmed that an obvious stress singularity phenomenon occurs after the unit size is less than 5 mm, that is, as the unit size decreases, the total deformation size increases rapidly. Therefore, the resolution of the finite element analysis is finally set to 5, and the unit size of the finite element analysis is 10 mm. Based on this parameter design, the automatic partitioning function generates a total of 19,156 nodes and  
Figure 7: Test scenario at \(-40\)\({}^{\circ}\)C.  
78,580 units. The first step in strength analysis is to perform static analysis on the structure. The static structure module is used for static analysis, and deformation and stress are set as solving terms. The results show the equivalent stress of the rudder system structure in a static state, as shown in Figure 8.  
According to the stress map results, the maximum stress in the rudder structure is at the guiding tie rod, and static stress analysis and fatigue analysis are separately performed for this component. In ANSYS, mesh delineation and force analysis of the guiding tie rod are performed, and the results are shown in Figure 9. The middle part of the tie rod has the highest stress, and its contact area with the tie rod head also presents the highest stress, which further indicates that the tie rod is the component of most concern. Considering the low-temperature environment, the components are imported into Ncode Designlife. The connecting head hole of the guide rod is fixed, pressure is applied to the other end of the joint, and its fatigue life under temperature conditions of room temperature, \(0\ ^{\circ}\mathrm{C}\), \(-20\ ^{\circ}\mathrm{C}\), and \(-40\ ^{\circ}\mathrm{C}\) is simulated. Their simulation cloud diagrams are shown in Figure 10. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Materials**} & **Density** & **Tensile** & **Yield** & **Young’s** & **Poisson’s** \\  & **(g/m\({}^{3}\))** & **Strength** & **Strength** & **Modulus** & **Ratio** \\  & **\(\sigma\)b (MPa)** & **\(\sigma\)s (MPa)** & **Y (GPa)** & **\(\sigma\)v** \\ \hline
925A & 7.938 & \(\geq\)630 & \(\geq\)310 & 213 & 0.3 \\
20\# & 7.84 & \(\geq\)410 & \(\geq\)245 & 206 & 0.282 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Mechanical property parameters of specimen material. Figure 8: Static stress analysis cloud diagram of the rudder system. Figure 9: Mesh delineation and static stress simulation analysis of the rudder: (**a**) tie rod grid division; (**b**) static stress analysis of tension rods in ANSYS. The results of the simulation analysis show the following:  
1. The areas where fatigue damage may occur in the rudder rod mechanism are located at the welded connection between the tie rod head and the connecting rod and the guide tie rod step. 2. There is no significant difference in the fatigue life of the rudder bar mechanism when the temperature is 20 \({}^{\circ}\)C and 0 \({}^{\circ}\)C.
3.