# Forming Difficulty Evaluation for Curved Hull Plates Based on Grey Relational Analysis
## 4 Calculation and Verification of Difficulty Evaluation for Real Hull Plates
### Rationality Analysis of Difficulty Evaluation Results of Forming Complex Curved Hull Plate  
Based on the above method, the forming difficulty of the real plate of a 3900 TEU container ship is calculated. The more difficult the curved plate forming is, the more forming time is required, the forming difficulty \(B_{k}\in[0,1]\). When the forming difficulty is close to 0, it means that the plate is extremely easy to form. When the shaping difficulty is close to 1, it means that the plate is extremely difficult to form. According to the geometric data and forming parameter data of different curved plates, the evaluation results are analyzed. According to the results, two groups of data with large difference in forming difficulty are selected for comparison. Among the nine real curved hull plates, the forming difficulty value of plate 1031-CPA2-1P is 0.240, which is the smallest. Therefore, the forming difficulty of plate 1031-CPA2-1P is the smallest. The forming difficulty value of plate 1021-CPA1-7P is 0.693, which is the largest. Therefore, the forming difficulty of plate 1021-CPA1-7P is the smallest. The geometric data, forming parameter data and forming difficulty results of the two curved plates are shown in Table 4. The shape and spatial position of the curved plate are shown in Figure 11. Compared with plate 1031-CPA2-1P, plate 1021-CPA1-7P is more difficult to be formed because it has longer  
Figure 10: Comparison of evaluation results of forming difficulty and forming time before and after improvement. plate length, wider plate width, larger deflection to be formed, more heating lines, and longer forming time required. In order to further analyze the difficulty evaluation results of forming, two curved plates with similar forming difficulty are selected for data comparison. The result of forming difficulty of plate 1021-CPA1-5P is 0.609, and the total forming time is 1719s. The result of forming difficulty of plate 1021-CPA1-3P is 0.483, and the total forming time is 1348s. The geometric data, forming parameter data and forming difficulty results of the two curved plates are shown in Table 5. The shape and spatial position of the curved plates are shown in Figure 12. The length, width and thickness of the two plates are similar. The deflection of plate 1021-CPA1-5P to be formed is about twice that of plate 1021-CPA1-3P. Therefore, the number of heating lines of plate 1021-CPA1-5P is more than plate 1021-CPA1-3P and the forming difficulty of plate 1021-CPA1-5P is bigger than plate 1021-CPA1-3P. \begin{table}
\begin{tabular}{c c c c} \hline
**Plate Name** & **Unit** & **1021-CPA1-7P** & **1031-CPA2-1P** \\ \hline Plate length & m & 6.629 & 5.098 \\ \hline Plate width & m & 1.905 & 1.418 \\ \hline Plate thickness & m & 0.022 & 0.020 \\ \hline Radius of curvature & m & 3.678 & 3.353 \\ \hline Deflection & m & 0.083 & 0.017 \\ \hline Heating lines number & & 15 & 4 \\ \hline Number of heating line difference & & 1 & 0 \\ \hline Heating line spacing & m & 0.780 & 1.699 \\ \hline Heating speed & \(10^{-3}\) m/s & 2.27 & 2.16 \\ \hline Forming time & s & 2640 & 464 \\ \hline Forming difficulty & & 0.693 & 0.240 \\ \hline \end{tabular}
\end{table} 
Table 4: Comparison of geometric parameters, forming parameters and forming difficulty of curved plates with large differences in forming difficulty. Figure 11: Two curved plates with a large difference in forming difficulty. The grey relational analysis method is based on the data of curved plates to be evaluated. The relationship between influencing factors and the processing difficulty is evaluated by calculating the correlation degree between the influencing factors. The maximum and minimum values of each influencing factor need to be determined in this method. If the plate changes, the data of the evaluation model may change. Therefore, the forming difficulty evaluation program for curved plate is developed. To ensure the accuracy of the calculation results for the forming difficulty of curved plates, the program can update the data of the curved plate to be evaluated.