# Improved Design of LNG Marine Loading Arm Docking Method Based on TRIZ Theory
## 4 Innovative Design of Problem-Solving Method Based on TRIZ
### The Method of Numerical Analysis Is Adopted for Innovative Design
#### 4.6.3 The Results after Optimization  
Finite element analysis was carried out to assess the improved structure, and Tables 7 and 8 show the relevant parameter changes before and after the improvement. The improved rope wheel structure exhibits a 59.34% reduction in mass and a 41.9% reduction in maximum wind face surface area compared to the initial structure. This reduction in the wind face area is advantageous in mitigating the influence of wind on the marine loading arm. However, the maximum stress and deformation of the rope wheel are increased after the improvement. Nonetheless, the yield limit of the improved structure, which is 355 Mpa, satisfies the requirements for strength and stiffness. In terms of the counterweight support, the total mass of the improved mechanism is 29.38% compared to the initial structure  
Figure 19: Optimization process of counterweight support.  
Figure 17: Stress cloud diagram of topological targets. (**a**) Rope wheels; (**b**) counterweight support.  
Figure 18: Rope wheel optimization process.  
mass, with a 52.95% reduction in the mass of the optimized region. The maximum stress and maximum total deformation are only slightly increased, meeting the requirements for strength and stiffness. The surface area of the optimized region is reduced by 52.7%, which effectively reduces the impact of wind.  
Due to variations in the pressure exerted on the marine loading arm at different positions, the LNG marine loading arm was divided into \(n\) regions for separate calculations. The more regions the arm is divided into, the more accurate the calculations will be. However, for the sake of convenience, the LNG marine loading arm was divided into 20 regions, as shown in Figure 20. The wind force acting on the marine loading arm can be expressed as follows:  
\[F_{i}=S_{i}\big{(}P_{i}-P_{i}^{\prime}\big{)} \tag{12}\]  
\[F_{all}=\sum_{i=1}^{n}S_{i}\big{(}P_{i}-P_{i}^{\prime}\big{)} \tag{13}\]  
where \(F_{i}\) represents the wind force of the LNG marine loading arm at the detection position, \(S_{i}\) is the ratio of the area to the detection area, \(P_{i}\) is the pressure in the high-pressure area of the LNG marine loading arm, \(P_{i}^{\prime}\) is the pressure in the back-pressure area of the LNG marine loading arm, and \(F_{all}\) represents the total wind force of the LNG marine loading arm.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Upper and Lower Rope Wheels** & **Initial Structure** & **Improved Structure** \\ \hline Mass (kg) & 700.97 & 285.01 \\ Maximum windward surface area (m\({}^{2}\)) & 1.24 & 0.72 \\ Maximum stress (MPa) & 3.10 & 12.47 \\ Maximum total deformation (mm) & 0.008 & 0.017 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Comparison of relevant parameters of upper and lower rope wheels before and after improvement.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Counterweight Support** & **Initial Structure** & **Improved Structure** \\ \hline Mass (kg) & 693.70 & 326.34 \\ Surface area (m\({}^{2}\)) & 1.10 & 0.52 \\ Maximum stress (MPa) & 19.64 & 21.149 \\ Maximum total deformation (mm) & 0.25 & 0.43 \\ \hline \hline \end{tabular}
\end{table}
Table 8: Comparison of relevant parameters of counterweight support before and after improvement.  
Figure 20: Detection and analysis of the position distribution of the LNG marine loading arm. (**a**) Structure before improvement; (**b**) structure after improvement.  
According to the data in Table 9, it can be calculated that the total wind force acting on the LNG marine loading arm assembly before optimization is 27.7 KN. After optimization, the total wind force is reduced to 19.9 KN, representing a wind force reduction of 28.1%.