In modern naval warfare, advancements in weaponry have significantly increased the vulnerability of ships to explosion impacts. Precision-guided weapons, in particular, pose a significant threat, as internal explosions within ship cabins can cause extensive damage to thin-walled structures. This damage not only compromises the ship's structural integrity but also affects its overall functionality and safety. To accurately assess a ship's ability to withstand such damage and make informed battlefield decisions, it is crucial to evaluate the residual load-bearing capacity of damaged structures under complex sea conditions. This analysis is essential for evaluating the ship's damage tolerance and determining its ability to safely return to port.

This study focuses on the behavior of hull plates damaged by in-cabin explosions. A series of meticulously designed model tests were conducted, aiming to analyze the residual load-bearing capacity of thin plates exhibiting dent damage under biaxial compression. The use of biaxial compression is highly relevant, as it replicates the complex stress states experienced by ship hulls in actual sea conditions. To measure the detailed mechanical behavior of the damaged plates, the digital image correlation (DIC) method was employed. This advanced technique enabled the creation of a three-dimensional full-field strain measurement system, which recorded the out-of-plane deformation of the plates with high precision. By analyzing this data, the study explored the failure modes of dent-damaged thin plates under biaxial compression, illuminating the mechanisms through which such damage progresses and ultimately leads to structural failure.

The experimental results provided significant insights into the behavior of damaged thin plates under biaxial compression. A key finding was that, regardless of the applied loading ratio, the presence of dent damage led to a substantial reduction in the residual load-bearing capacity of the thin plates. In some cases, this reduction reached up to 19.96%, demonstrating the severe impact of even minor damage on the structural performance of the plates. Furthermore, all tested plates ultimately failed due to significant plastic deformation at the intersection of the loading edges, which underscores the localized nature of the damage and its catastrophic consequences for structural integrity. Another key finding was that an increase in the load at one end of the biaxial compression resulted in a notable decline in the ultimate bearing capacity at the other end.

This study provides valuable insights into assessing the damage survivability of ships under complex stress conditions. The findings help naval personnel better understand the structural state of damaged ships, enabling them to make informed decisions regarding mission continuation or safe return to port. Additionally, the research provides a basis for future research focused on optimizing ship structural design and enhancing damage-tolerance capabilities. Overall, this study plays a vital role in ensuring the safety and operational effectiveness of ships in combat and their safe return to port.

This study aims to advance the development of composite drag reduction technology involving super-hydrophobic surfaces and bubbles by investigating the coalescence characteristics of bubbles on wetting surfaces and revealing the effects of surface wettability, bubble spacing, and bubble size on bubble coalescence.

A numerical model of bubble coalescence on an underwater wetting surface is established based on the volume of fluid (VOF) method. The coalescence and spreading characteristics of bubbles on different wetting surfaces are analyzed by varying the surface contact angle, bubble spacing, and bubble size. The accuracy of the simulation results is validated by comparing them with experimental data.

The results show that increasing the contact angle of the wetting surface and decreasing bubble spacing facilitate bubble coalescence, while increasing bubble size slows down the spreading speed of bubbles on the surface and is not conducive to accelerating bubble coalescence. Specifically, when the contact angle increases from 130° to 170°, the initial coalescence time of bubbles decreases from 5.6 ms to 3.2 ms (a reduction of 42.9%), and the maximum spreading distance of bubbles increases from 6.53 mm to 9.4 mm (an increase of 138%).

The findings provide a theoretical basis for the coupling design of super-hydrophobic surfaces and bubble drag reduction technology. Optimizing surface wettability and bubble spacing can significantly enhance bubble coalescence, thereby improving the stability and efficiency of bubble drag reduction.

In order to improve the actual efficiency of microbubble drag reduction technology, this study develops intelligent airflow control technology for microbubble drag reduction based on an improved ant colony optimization (ACO) algorithm.

Based on the mechanism of microbubble drag reduction, the ideal optimal airflow rate at different speeds is obtained by carrying out microbubble drag reduction tests on a self-developed ship model prototype. The software system of intelligent airflow control technology is developed by employing the improved ACO algorithm. A self-propelled test on a ship model installed with an intelligent control hardware system is carried out to verify the actual drag reduction effect of this technology.

The technology proposed in this study can effectively control the airflow to reach the optimal microbubble drag reduction condition, and can also monitor the speed change and adaptively control the airflow to achieve the best drag reduction conditions at various speeds.

This technique improves the automation and intelligence level of microbubble drag reduction technology while enhancing its actual efficacy.