PSI - Issue 5

Jung Min Sohn et al. / Procedia Structural Integrity 5 (2017) 935–942 Aditya Rio Prabowo et al. / Structural Integrity Procedia 00 (2017) 000 – 000

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4. Results and discussion

This section presents simulation results of the defined scenarios calculated by the finite element method. Discussions are divided according to crashworthiness criteria, including internal energy, resultant force and damage extent during the struck ship experiences side collision.

4.1. Internal energy

The internal energy is defined as the energy which is needed to crush the side structure during penetration of the striking ship. Higher magnitude of this energy will affect the resultant force. Based on the graph in Fig. 4, the highest energy appeared during deck-collision was deployed as a defined scenario model. This result occurs as the striking ship was hardly penetrating the side structure which was strengthened by the upper deck of the struck ship. The upper deck acted as an important structural component which successfully provided the highest resistance to the side structure against side collision. In the second place, the shell-collision provided similar tendency as the deck-collision but with smaller magnitude. The energy increment of the shell-collision was not as high as the deck-collision since there was no major longitudinal member that strengthened this location. The results also indicated that the deck collision which was located upper than the shell-collision began the impact 0.05-0.08 s earlier. This tendency was confirmed by geometry of the struck ship. A higher location would have wider breath than parts near the bottom structure. Therefore, impact between the bulbous bow of the striking ship and the struck ship in the shell-collision occurred later than the deck-collision since the bulbous bow contacted the lower location (nearer to the bottom structure) than target location in the deck-collision. Despite of these distinctions, similarity in the energy magnitude indicated that the both collision models produced similar penetrations which the striking ship successfully impacted the upper and lower parts of the struck ship. In other hand, remarkable differences in terms of magnitude and tendency were shown by the over deck-collision . In this collision model, the energy magnitude was not increasing as found on the deck-collision and shell-collision after passing 0.15 s . In this time point, contact between the striking ship and the upper part of the struck ship was begun for other collision models besides the over deck-collision. As no further contact happened on the upper part, penetration focused on the lower part which involved the bulbous bow and side structure.

Bulbous bow penetrates the lower part of the struck ship

Deck-collision

Shell collision

Over deck-collision

Fig. 4. The internal energies during penetration of the striking ship for different target locations.

4.2. Resultant force

Verification of the energy behaviors is presented by the resultant force in Fig. 5. In terms of the initial impact, timing of all proposed models for the energy and force showed good correlation as time sequences of impacts happened according to the location of the targets. The shell-collision on the lowest location produced the latest

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