Based on the classic honeycomb sandwich structure, an enhanced honeycomb lattice sandwich structure was proposed in this paper, and its load-bearing performance was analyzed and optimized. Firstly, unit cell specimens of both classic and enhanced honeycomb structures were fabricated using 3D printing technology. Quasi-static compression tests and numerical simulations were conducted to verify that the enhanced honeycomb unit cells have superior load-bearing performance compared to the classic honeycomb unit cells. Secondly, five key parameters of the enhanced honeycomb were selected as design variables to create a Kriging surrogate model for structural mass and a radial basis function neural network model for energy absorption. Multi-objective genetic algorithms were used to invoke the surrogate models for optimizing load-bearing performance. The optimal structural parameters of the enhanced honeycomb unit cells were obtained and validated through experiments and simulations. The results show that, under the same mass conditions, the optimized configuration improves energy absorption performance by 24.25% compared to the initial configuration and by 35.9% compared to the classic honeycomb sandwich structure.

Aiming at the practical application of I-core metal sandwich structures in the main hull section, the four-point bending ultimate bearing capacity test of a I-core metal sandwich composite cabin model was carried out. The failure mode and ultimate bending moment of the I-core metal sandwich composite cabin model were obtained by test, and the test results were in good agreement with the nonlinear finite element calculation results. Test results show that the failure of I-core metal sandwich structure is dominated by the overall buckling while the local buckling is secondary. Meanwhile, I-core metal sandwich structure has a high load bearing capacity and can replace the deck and side stiffened plates in the hull structure. In addition, the metal sandwich composite cabin model is successfully manufactured, which verifies the feasibility of the application of metal sandwich structure in hull structure.

The stability of thin plates plays an important role in ship design and strength check. To investigate the shear stability of ship's thin plates, a picture frame fixture was designed to conduct an in-plane shear buckling test on square thin plates. In the test, 3D Digital Image Correlation (3D-DIC) was used to obtain mechanical response information such as load-end elongation curve, full-field displacement/strain, etc. The load-end elongation relationship reveals the load-bearing characteristics of the thin plate under in-plane shear condition and determines the critical load for buckling instability. According to the displacement and strain field information of the thin plate at typical moments, it is found that the normal deformation of the thin plate increases with the increase of in-plane shear load. After the instability of the thin plate, there are three half-waves symmetrically distributed along the vertical diagonal, and the internal wave amplitude is greater than the external wave amplitude. The strain waveform and contour plot tend to stabilize during the post-buckling process. By analyzing the response curves of the normal displacement and Mises strain at the key points of the thin plate with time, a new method for identifying the buckling instability of in-plane sheared thin plates was proposed and verified. This study provides a useful reference for experimental research and mechanical behavior analysis of in-plane shear stability for ship’s thin plates.

The extreme polar marine environment is harsh and the ice conditions are complex, requiring sufficient structural strength for navigation safety of ships. Existing design specifications and monitoring guidelines for polar ships senerally only consider the ultimate strength within the elastic phase of material under single loading conditions, resulting in overly conservative strength design. The ultimate bearing capacity of polar ship structures were analyzed based on the Combined Theory of Strength and Stability (CTSS) and plastic failure models, and a calculation formula for the ultimate strength of typical structures was derived in ship-ice collision areas under plastic deformation conditions. By using the finite element analysis method, a numerical analysis model for the ultimate strength of structures was established. By comparing the theoretical and numerical results, it was found that the theoretical calculation formula is highly accurate and can be used as a quick verification method for the ultimate bearing capacity of polar ship structures. Besides, with reference to the design requirements of specifications, the article provides recommendations for the arrangement of rib space in the ice belt areas of various ice-class ships based on the theory of ultimate strength, providing reference for the design of the ultimate strength of polar ship structures.

In this paper, a theoretical formula of plastic deformation and impact force of rectangular lightweight sandwich plate struck by a rectangular frustum impactor was derived based on the approximate yield criterion and rigid-perfectly plastic theory. Numerical simulations were conducted to verify the accuracy of the analytical prediction model. In addition, the influences of load distribution, side length ratio and location of impact loads on the dynamic response of a rectangular sandwich plate were theoretically analyzed. Results show that the theoretical predictions for PVC foam core sandwich plate struck by a rectangular frustum impactor show good agreement with numerical results. With the increase of load distribution coefficient, the impact strength per unit area decreases, which leads to the decrease in plastic deformation; when the impact position is closer to the boundary, the length of plastic hinges increases, resulting in a significant decrease in deformation; the plastic deformation achieves its most significant value under impact when the aspect ratio of foam sandwich plate is 1.

Some ship equipment with weak anti-shock properties has the flowing characteristics such as small space proportion, variable and large shock loads, dynamic load changes, rigid-flexible state transitions and passive operation. Howerver, these needs cannot be met by traditional vibration isolation devices. Therefore, this paper proposed a novel integrated bi-directional vibration isolation device and conducted the corresponding structural design. Then, the dynamic model of the vibration isolation device was established to predict the dynamic response under complex loading and to explore the effects of frequency and damping ratio on the anti-shock properties of the device. Finally, the test bench for the vibration isolation device was built to verify the validity of the structural design and theoretical analysis. The results show that the direction of the impact load and dynamic sway load affects the anti-shock properties of the vibration isolation device, When the loads act in the same direction, the anti-shock performance will be improved, whereas when the performance will be decreased if the loads act in opposite directions. As the frequency or damping ratio increases, the anti-shock properties of the vibration isolation device gradually decrease, thus requires optimization based on key performance indicators. The test results of the vibration isolation device have smooth curves without distortion, and the overall trend is basically the same as that of the theoretical calculation results, which can verify the validity of the structural design and theoretical analysis. The results of the study can provide useful guidance for the design of vibration isolation and anti-shock for weak ship equipment.

The acoustic analogy theory is currently the most significant theoretical framework in the field of flow acoustics, with widespread engineering applications. Thus, this paper focuses on the development history and engineering applications of the acoustic analogy theory, concentrating on the three core issues: sound sources, acoustic variables, and wave operators. It then analyzes and prospects the future research of the acoustic analogy theory, considering the major needs in China and adapting to the era of artificial intelligence. The purpose is to provide some useful references for scholars through the analysis and summary of the acoustic analogy theory, and also to offer possible solutions for some engineering problems.

The main ballast tank is an important component of a submarine submerging and surfacing system. To correctly simulate the working process of a submerging and surfacing system, modeling and simulation analysis of the main ballast tank based on MWorks were carried out. Firstly, the models of water injection system, conventional blowdown system and emergency blowdown system were built using MWorks. Then, the model’s reliability was verified by comparison with CFD simulation results. Finally, the impact of factors such as back pressure and sea opening area on the injection and drainage process of the main ballast tank was analyzed. The results show that the relative error of main ballast tank blowing time between the MWorks simulation results and the CFD simulation results is within 10%; increasing back pressure will increase the blowing time and reduce the structural strength requirements for the main ballast tank; increasing the sea opening area will reduce the filling time, blowing time and the structural strength requirements for the main ballast tank. The main ballast tank system models built with MWorks have fast calculation speed and accurate regularity characteristics, which facilitates the rapid adjustment of engineering design parameters to determine design input.

A rapid design method for a marine propeller with an arbitrary radial circulation distribution was proposed in this paper. Based on the lifting surface model, a genetic algorithm was employed to design the pitch and maximum camber distributions, using given camber line shapes, aiming to achieve a chordwise distribution of circulation that is as close as possible to the specified one. Subsequently, the design problem related to specified chordwise circulation distribution was solved, the redesign process of which starts with the above designed propeller. The camber line shape of each blade section was corrected according to the difference between current chordwise circulation distribution and the specified one, so that the circulation distribution of the designed propeller converges iteratively to the expected one. By applying these methods, a five-bladed highly skewed propeller was redesigned under open water conditions, and the design results were numerically validated with RANS simulation results. The hydrodynamic performances and pressure distributions of the designed propeller are in good agreement with the design objectives, thus indicating that the proposed design methods are simple, fast, and reasonably accurate.

In order to meet the needs of the evaluation and optimization of submarine near-surface navigation performance, this paper performs a numerical study on the hydrodynamic characteristics of a near-surface self-propelled submarine by using Reynolds-Averaged Navier-Stokes method. The volume of fluid model is used to capture the interaction between submarine and free surface, and the body force model is used to establish the propeller hydrodynamic model. At the same time, the controllers of propeller and stern rudders are constructed to control the speed and course of the submarine, and the numerical simulation of the submarine near-surface self-propulsion test is realized. The numerical simulation results are compared with the model test data and numerical simulation results from other literature, and the effectiveness of the established numerical method is thus verified. Through the numerical simulation of the submarine self-propulsion test under different immersion depth, the variation law of the submarine near-surface self-propulsion point with the immersion depth is revealed, and the internal mechanism is discussed by combining the flow field characteristics obtained from numerical simulation.