## 6 Results and Analysis
### Responses of Submarine Pressure Hull to Uindex
#### 6.2.1 The Acceleration Response at Different Locations
Furthermore, Figure 14 shows the acceleration time histories (\(A_{2}\)) in the vertical direction for nodes \(C\) and \(D\) which located at top and bottom of the MICEPH under the effect of 20 kg TNT charge located at offset distances of 5.5 m, 15.5 m and 20.5 m. It is revealed that the upper point (node \(C\)) moves in a direction opposite to that of the lower point (node \(D\)). The peak accelerations at node \(C\), measured downward, are \(-40\times 10^{3}\) m/s\({}^{2}\), \(-10.4\times 10^{3}\) m/s\({}^{2}\), and \(-7.37\times 10^{3}\) m/s\({}^{2}\) at offset distances of 5.5 m, 15.5 m, and 20.5 m, respectively. Likewise, the peak accelerations at node \(D\), measured upward, are \(49.2\times 10^{3}\) m/s\({}^{2}\), \(12.6\times 10^{3}\) m/s\({}^{2}\), and \(8.25\times 10^{3}\) m/s\({}^{2}\) at offset distances of 5.5 m, 15.5 m and 20.5 m, respectively. The peak acceleration time histories (\(A_{2}\)) at node \(D\) are higher than its counterpart at node C, while the frequencies of accordion and breathing motion are nearly the same. These results ensure that the accordion and breathing motion are directly correlated as per [2]. Figure 13: The acceleration-time history (\(A_{2}\)) at nodes \(E\) and \(F\) due to 20 kg TNT on the pressure hull. Similarly, Figure 15 shows the acceleration time histories (\(A_{2}\)) at nodes \(A\) and \(B\). It is observed that, once the shock wave struck the stand-off point at node \(A\), the vertical movements of nodes \(A\) and \(B\) follow the same direction. Node \(A\) moves first, followed by node \(B\). The peak acceleration at node \(A\) is \(-8\times 10^{3}\) m/s\({}^{2}\), \(-1.8\times 10^{3}\) m/s\({}^{2}\) and \(-1.3\times 10^{3}\) m/s\({}^{2}\) at offset distance of 5.5 m, 15.5 m and 20.5 m, respectively, and occur downward. Likewise, the peak acceleration at node \(B\) is \(-3.5\times 10^{3}\) m/s\({}^{2}\), \(-1.1\times 10^{3}\) m/s\({}^{2}\) and \(-0.81\times 10^{3}\) m/s\({}^{2}\) at offset distance of 5.5 m, 15.5 m and 20.5 m, respectively, following the same direction at point \(A\). Figure 16 plots the athwart acceleration time histories (\(A_{1}\)) at nodes \(A\) and \(B\) which is the primary direction of shock wave propagation. It is revealed that the shock wave arrives at node \(A\) first then hits node \(B\). The maximum athwart acceleration (\(A_{1}\)) at node \(A\) occurs in the horizontal direction and its peak is about \(52.4\times 10^{3}\) m/s\({}^{2}\) at an offset distance of 5.5 m. This is attributed to the release of the shock wave, occurrence of local cavitation and effect of bubble pulse. On the other hand, the second peak values, measured at offset distances of 5.5 m, 15.5 m and 20.5 m, occur owing to the uploading of the MICEPH. Similarly, the maximum athwart acceleration (\(A_{1}\)) at node \(B\) also occurs in the horizontal direction, and its peak is about \(29.4\times 10^{3}\) m/s\({}^{2}\), \(10.9\times 10^{3}\) m/s\({}^{2}\) and \(7.9\times 10^{3}\) m/s\({}^{2}\) at offset distance of 5.5 m, 15.5 m and 20.5 m, respectively. From the aforementioned analysis, it is concluded that the local cavitation has a major effect on athwart acceleration at standoff point at node \(A\). Likewise, the uploading of the structure and the first bubble pulse also have a major effect on athwart acceleration. Additionally, for nodes \(A\) and \(B\), the transverse responses are very severe at these locations, and the greatest acceleration occurs in the athwart direction, which is the main direction of shock wave with values of \(52.3\times 10^{3}\) m/s\({}^{2}\) and \(29.4\times 10^{3}\) m/s\({}^{2}\) at time intervals of 2 m/s and 4 m/s, respectively, followed by the vertical and longitudinal directions. While, for nodes \(C\) and \(D\), which located at the top and bottom of MICEPH, the peak acceleration occurs in the vertical direction with values of \(-40\times 10^{3}\) m/s\({}^{2}\) and \(49.2\times 10^{3}\) m/s\({}^{2}\) at time interval of 4 m/s, followed by the athwart and longitudinal directions.