Abstract
This paper presents an experimental investigation into the dynamic response of three free floating stiffened metal boxes with protective coatings subjected to underwater explosion (UNDEX). One box was kept intact while the other two were, respectively, covered with monolithic coatings and chiral honeycomb coatings. Three groups of live fire tests with different attack angles and stand-off distances were conducted. The acceleration on the stiffener and strain peak on the bottom hull were selected as the major comparative criterions. Test results show that the impulse transmitted to the structure at the initial stage can be reduced, owing to the coating flexibility and fluid-structure interaction mechanism. Consequently, the acceleration peaks induced by both shock wave and bubble pulse were reduced. The shock environment can be more effectively improved by honeycomb coating when compared with monolithic coating. Most of the strain peaks decreased to a certain extent, but some of them were notably manifested, especially for honeycomb coating. The test affirms the fact that soft coating can cause stress concentration on the shell that is in direct contact with the coating due to the impedance mismatch between the interfaces of materials. A softer rubber coating induces a greater magnitude of strain.
Highlights
In naval warfare, warship and submarine will inevitably suffer from underwater explosions
This paper presents an experimental investigation on the water blast responses of a free floating stiffened box before and after coatings are covered onto its bottom hull with different attack angles and stand-off distances
Many other methods such as impact test can be used to study the performance of coating, but live UNDEX test is the most authentic way to evaluate the actual effect of the coating as the transient response of the hull with rubber coating subjected to underwater explosion is a very complex process, such as shock wave incidence and reflection, large deformation, hull motion, and strain and strain rate dependent behavior
Summary
Warship and submarine will inevitably suffer from underwater explosions. Sandwich plates and beams have higher shock resistance than monolithic counterpart of equal mass under shock loading in both air and water [4,5,6,7,8,9,10,11,12,13] Based on these results, sandwich coating has drawn much attention to the blast protection of ship subjected to noncontact underwater explosion. Experimental research by Chen et al [18] on the response of neoprene coated cylinder subjected to underwater explosions showed that, after the rubber layer is coated, the strain on the outer hull is notably manifested, especially in the hoop direction.
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