## 4 Results and Discussion
### Dummy Cell Stack Simulation and Experimental Results  
Table 5 illustrates the strains of the end and middle cells of the 21-cell stacks to which the conventional circular end plate and CN0510 end plate, which was optimized by the parametric study, were applied. The strain ranges are similar at the end and the middle cells of the stacks, respectively, between the conventional and CN0510 end plates. The wavy shape inside on the end cell occurred because the upper cut of the sector formed, which disappeared on the middle cell with CN0510 end plates. The outside of the cell was bent and appeared severely deformed with more than 0.001 of strain. Experimental results of pressure sensing films for circular end plate dummy cells have similar distribution of pressure. Both end plates pressed inside (pink) of the dummy cells lighter than outside (strong red). Furthermore, after comparing the cells located in the middle of the stacks to which the conventional circular end plate had been applied and those to which the CN0510 end plate had been applied, the strain was smaller, and the color was more uniform than for the end cells. The clamping pressure was uniformly applied to the end plates; thus, the CN0510 end plate and uniform clamping pressure were equivalent to that of a conventional circular end plate. The strain of the end and the middle cells of the stacks in which the conventional square end plate and those in which the CN10 end plate, which was selected from the parametric study, were applied, can be confirmed from Table 6. The strain of the end and the middle cells of the stacks with the  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **Equivalent Strain from Simulations** & **Measured Pressure Distribution** \\ \hline End cell & 0.000185 & 0.000185 \\ (Conv.) & 0.00024 & 0.00024 \\ (Conv.) & 0.000326 & 0.000326 \\ (Conv.) & 0.000036 & 0.000036 \\ (Conv.) & 0.000036 &  
conventional square end plates and those with the CN10 end plate are at the same level, while the strains of the square end plates are 10 times larger than those of the circular end plates. The outside of the cell was bent and appeared severely deformed similar to the circular end plates. Furthermore, for cells located in the middle of the stacks with the conventional square end plate and those with the CN10 end plate, after comparing the end cells with rectangle contour inside, the strain was smaller, and the contour was circular. Evidently, the clamping pressure was applied uniformly, and so the square end plate with less weight and uniform clamping pressure was equivalent to that of the conventional square end plate. The contour distribution and color uniformity were confirmed by the experimental results with pressure sensing films. Figure 7 is a graph comparing each of the four types of stacks in which conventional circular, CN0510, conventional square, and CN10 end plates had been applied. For the middle cell, the deviation of the strain is much smaller than at the end cells. The minimum strains of the middle cells are nearly zero, which can result in high ohmic resistance. \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Equivalent Strain from Simulations** & **Measured Pressure Distribution** \\ \hline  & & \\ End cell & 0.0012453 & \\ (Conv.) & 0.0009067 & \\ (CN10) & 0.0001233 & \\ (CN10) & 0.000356 & \\ (Conv.) & 0.0005867 & \\ (Conv.) & 0.00013679 & \\ (CN10) & 0.00014227 & \\ Middle cell & 0.001089 & \\ (CN10) & 0.0001333 & \\ (CN10) & 0.00013679 & \\ (CN10) & 0.00025847 & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Comparison of the simulated equivalent-strain distribution with the experimental pressure distribution, using the square end plates of the dummy-cell stack. Figure 8 confirms the strain tendencies for each cell. In Figure 8, the stack applied with the conventional circular and CN0510 end plates had less strain at both ends of the cell compared with the stack with the conventional and CN10 end plates.