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Fig. 13. The plastic zone progress of the patrol-boat subjected to underwater shock.

From the same paper as the previous 2 slides.

When the ship is subjected to the serious underwater explosion KSF=0.8, the structure will respond into the plastic range. Fig. 13 depicts the plastic zone spread diagram. This work selects W=576.0 kg and R=30.0 m, with the shock wave propagating towards the hull as spherical waves. Initially, the stress of the bottom structure at t=2.0–3.0 ms immediately exceeds the yielding stress and moves into the plastic range, with the effective plastic strain being approximately 7.0x10-3. Then the following yield region spreads through the fore-aft direction at t=4.0–16.0 ms. Meanwhile, the patrol boat oscillates between elastic and plastic states. Finally, the whole patrol boat recovers toward completely elastic state at t=20.0 ms.

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