# Forming Difficulty Evaluation for Curved Hull Plates Based on Grey Relational Analysis
## 5 Conclusions  
Based on the actual forming characteristics of complex curved hull plates forming, this paper proposes a method to evaluate the forming difficulty of complex curved hull plates based on grey relational analysis. The conclusions are as follows.  
1. Based on the grey relational analysis method, a difficulty evaluation model of complex outer hull plate forming is established. The grey relational analysis method is suitable for small sample data analysis. The weight of each influencing factor affecting the forming of complex outer hull plates is obtained by using the grey relational analysis method.
2. The forming difficulty of curved plates is negatively correlated with the length, curvature radius, heating line spacing and heating speed of curved plate. It is positively  
Figure 12: Two curved plates with similar forming difficulty.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Plate Name** & **Unit** & **1021-CPA1-3P** & **1031-CPA1-5P** \\ \hline Plate length & m & 6.654 & 5.343 \\ \hline Plate width & m & 1.943 & 1.623 \\ \hline Plate thickness & m & 0.020 & 0.022 \\ \hline Radius of curvature & m & 2.996 & 3.438 \\ \hline Deflection & m & 0.026 & 0.055 \\ \hline Heating lines number & & 8 & 14 \\ \hline Number of heating & & 2 & 2 \\ line difference & & & \\ \hline Heating line spacing & m & 1.331 & 0.668 \\ \hline Heating speed & \(10^{-3}\) m/s & 2.26 & 2.59 \\ \hline Forming time & s & 1348 & 1719 \\ \hline Forming difficulty & & 0.483 & 0.609 \\ \hline \end{tabular}
\end{table}
Table 5: Comparison of geometric factors, forming parameters and forming difficulty of curved plates with close forming difficulty.  
correlated with the thickness, width, overall deflection, number of heating lines and the difference of heating lines on both sides of the curved plate. The number of heating lines has the greatest influence on the forming difficulty. The heating speed has the least influence on the forming difficulty.
3. The evaluation model can calculate the forming difficulty of the outer hull plate according to the geometric data and forming parameter data. The comparative analysis of the difficulty evaluation results of the curved plate forming and the forming time verifies the rationality of the evaluation model. When the outer hull plate is divided into plates, the longer the plate length and the shorter the width, the smaller the forming difficulty. The deflection difference on both sides of the curved plate should not be too large. The smaller the deflection, the smaller the difficulty of forming the curved plate.  
This research can quantify the difficulty of forming complex outer hull plates and provide reference for the division of outer hull plate.  
Conceptualization, S.W., Z.X., J.W., R.L. and Y.W.; methodology, S.W., Z.X., J.W., R.L. and Y.W.; writing--original draft preparation, S.W., Z.X. and Y.W., writing--review and editing, S.W., Z.X. and J.W., visualization, Z.X. and Y.W., validation, J.W. and R.L.; funding acquisition, S.W., J.W. and R.L. All authors have read and agreed to the published version of the manuscript.  
This study was supported by the Fundamental Research Funds for the Central Universities (Grant No. 3130202119), the National Natural Science Foundation of China (Grant No. 51009025), the High Technology Ship Scientific Research Project of Ministry of Industry and Information Technology of China (Grant No. [2018]473) and the Major Project of Science and Technology of Liaoning Province (Grant No. 2019)H1/10100025).  
Not applicable.  
All data that support the findings of this study are available from the corresponding author upon reasonable request.  
The authors declare no conflict of interest.