## 4 Analysis of Calculation Results
### Effect of Explosive Chamber Structural Dimensions on the Transition from Damage Mode III to Mode IV  
The damaged C-planes (y-z direction plane) for the E-I and E-III models are shown in Figure 7. The effective plastic deformation curves of the model points are shown in Figure 7c. When the E-I model was subjected to a TNT equivalent W = 25 kg implosion, \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Explosion** & **Wall** & & & **Non-** & & **Dimensionless** & \\
**Equivalent** & **Dimensions** & **\(\gamma\)** & **Area (m\({}^{2}\))** & **Dimensional** & **Deflection** & **Dance Mode** \\
**W (kg)** & **\(a\times b\) (m)** & & & & **\(D_{in}^{\prime}\)** & **(\(\omega\cdot\)h\({}^{-1}\))** & \\ \hline
6.25 & 1.2 \(\times\) 1.2 & 1 & 1.41 & 0.872 & 10.33 & Center breach \\
6.25 & 1.697 \(\times\) 0.848 & 2 & 1.41 & 0.872 & 6.66 & Plastic large deformation \\
6.25 & 2.4 \(\times\) 0.6 & 4 & 1.41 & 0.872 & 3.4 & Plastic large deformation \\ \hline \hline \end{tabular}
\end{table} 
Table 7: The damage features of the same area & different aspect ratios of the wall plates. Figure 6: The variation of deflection, velocity, and pressure at different marker points. (**a**) Variation of deflection; (**b**) Variation of velocity; (**c**) Variation of pressure. the central deformation of the plates increased rapidly. At t = 0.75 ms, there was almost simultaneous tearing of the bulkhead plate edges and detachment from the structure, while flap fractures were produced in the box structure's corners. Comparing the damage of the E-III test model, the C-plane with the largest area and smallest blast distance is the first to form a central breach (mode II), with an effective plastic strain of 0.268. The A-plane experiences tearing that starts in the middle of the long edge and spreads to the corners, but the central portion of the plate maintains a relatively flat shape during failure. Deformation is primarily concentrated near the boundary with an effective plastic strain of 0.0896, which shows a tensile tear at the edge of damage mode III. The B-plane has a smaller area, a lower mass, and a higher beginning velocity. The damage is more restricted to the support, the wall plate center deformation is also the smallest, and the effective plastic strain is 0.033, which shows shear damage (mode IV). Plastic deformation of the rectangular plates is observed under strong impact loadings, mainly bending that yields at the midpoint of the long side, tensile yielding in the center of the plate, and easy shear yielding for a smaller mass area of the wall plates. [PERSON] (2016) proposed that the critical velocity for the transformation of damage mode III to mode IV depends only on the material properties and corresponds to the \(\frac{W}{hubp}\) part of the modified non-dimensional, where the ratio is the explosive charge to the mass of the wall plates. Under the same implosion loads, the same material wall plate, with a smaller area, is easier to reach the critical velocity and easier to occur shear damage. As shown in Figure 7b, the damage to the different wall panels in the E-III test chamber is different and distinguishes the first damage location, which can be divided into the center of the wall panel, the midpoint of the edge, and the corner. Under imposed load and inertia force, the fracture expands in different ways due to different energy consumption and different final fracture sizes. In reference to the crack classification mode, according to the relationship between the stress and the direction of the crack expansion surface, the extension mode of the break can be divided into three categories. (a) Open type (Type I) crack: positive stress is perpendicular to the crack face, and the direction of expansion is perpendicular to the stress.