## 4 Analysis of Calculation Results
### Effect of Structural Dimensions on the Transition from Damage Mode I to Mode II  
Figure 5 shows the damage results of the E-I, E-II, and E-IV test models subjected to the internal explosion with a TNT equivalent \(W=6.25\) kg. Points a, b, and c are the center unit of the A-, B-, and C-plane plates of the model structure. Point d is the cell in the B-plane (x-z direction) of the E-II model, approximately 15 cm from point b along the positive direction of the z-axis. After the explosion, the pressure pulse impacted the plates of the blast-loaded cabin in the E-I model. The plastic hinge lines were produced on the two diagonals and gradually approached the center. At this stage, the central unit accelerates, the deflection becomes greater and a plastic hinge ring is formed. When the pressure pulse reaches the static plastic collapse pressure, the wall plate is not further damaged.The central units of the wall plates were no longer accelerated, and the plastic deformation consumed the kinetic energy of the system. When the deformation in the region exceeded the fracture strain, the center of the wall plates produced a breach, as shown in Figure 6a. Comparing the damage feature of the anisotropic multi-cabin structures with the same volume and different structural dimensions, the E-II model had a larger C-plane in the blast-loaded cabin, a smaller explosion distance, and larger kinetic energy that was consumed in the plastic deformation process. Until the velocity of unit deceleration is nearly 0, the strain in the central region does not exceed the fracture strain, the C-plane plates had not observed a breach in the center, and deformation slowly converged to a normal value. The units of the B-plane plate accelerated under the pressure impulse and plastic deformation consumed kinetic energy. In the process of unit deceleration, at \(t=1.8\) ms, the units of the B-plane plate had not decelerated to 0, it was subjected to the second impulsive loadings, and the wall plates were further damaged after the original deformation. Near the plastic hinge ring d point at the weaker stress concentration, which was the first to be destroyed to form the pressure relief port, energy was consumed and released without causing further damage to other wall plates, as shown in Figure 6b. Compared with the E-I and E-II test models, the C-plane plate of the blast-loaded cabin in the E-IV model was much larger and the explosion distance was smaller. The process of generating plastic hinges and gathering them to the center of the plates consumed more energy. The remaining energy did not make the other wall plates produce a significant break, and the large plastic deformation were observed on the walls, as shown in Figure 6c. The analysis above indicates that the transformation of the wall plates from damage mode I to mode II under internal blast loadings is mainly the transformation and consumption between explosive energy, the kinetic energy of the wall plate units, and plastic deformation energy. The strain energy of a plate is expressed as _crabab_ in [PERSON]'s study [14], where \(\sigma\) is yield stress, \(\varepsilon\) is the average strain, \(h\) is the thickness, and \(a\) and \(b\) are the length and width, respectively. In the non-dimensional number \(D_{in}^{*}\), \(\frac{E}{h\hbar\omega_{y}}\) is the ratio of explosive  
Figure 5: Damage of multi-box structures of different structural dimensions (Unit: cm): (a) 120 \(\times\) 120 \(\times\) 120; (b) 84.8 \(\times\) 169.7 \(\times\) 120; (c) 60 \(\times\) 240 \(\times\) 120.  
energy to the deformation energy, and the transformation of damage occurs when a wall plate with different areas exceeds the limit strain under internal blast loadings. The aspect ratio will also influence how the damage mode transforms the same area with different wall plate aspect ratios, as demonstrated in Table 7 for the same internal blast equivalent damage effect for the same area with different wall plate aspect ratios.