In response to the problems of excessive measurement points and low nonlinear segment reconstruction efficiency in the deformation field reconstruction of ship structures, this paper proposes a deformation field reconstruction method (iFEM-PSO) based on dynamic measurement field optimization combining inverse finite element method (iFEM) and particle swarm optimization algorithm (PSO). Taking three typical hull plate structures of flat plates, open flat plates and open reinforced plates as objects, different order buckling modes are applied as initial defects to obtain different failure characteristics, and the reconstruction accuracy under the input of optimized measurement points and full measurement points is compared and analyzed. The results show that the iFEM-PSO method can reduce the number of required strain sensors by about 75%, and the overall reconstruction error remains within 15%, effectively verifying its accuracy and efficiency in nonlinear deformation reconstruction. The optimized measurement points are mainly concentrated in areas with large initial defects, structural boundaries and stress concentration areas (such as the periphery of the opening, the connection between the ribs and plates), and the reconstruction accuracy is proportional to the degree of failure, revealing the inherent correlation between the failure characteristics and the sensitive areas of the measurement point, and providing theoretical basis and technical support for the optimization arrangement of the reconstruction measurement points of the typical structural deformation field of the ship.

To address the issues of hypervelocity impact on composite sandwich panels and the evaluation of their post-impact residual strength, this study established a numerical calculation method for the hypervelocity impact behavior of composite sandwich panels and their post-impact residual strength, which incorporates multiple failure modes. A single-point impact case was designed, and hypervelocity impact tests were conducted using 7.5 mm cubic 45# steel fragments with an impact velocity of 1200 m/s ± 5%. Subsequent axial compression tests were performed on the impacted panels to determine their residual strength. The proposed numerical calculation method was implemented in the finite element software ABAQUS for simulation. The results indicate that the errors between the experimental and simulated values of residual velocity and maximum compressive load are both within 10%, thus verifying the effectiveness of the developed numerical calculation method. Based on this validated numerical method, the influence of the number of fragments on the post-impact residual strength of the sandwich panels was further investigated. Comparative analysis across different test cases reveals two key findings: first, the position of a single impact-induced breach has no significant effect on the residual strength of the composite sandwich panels; second, as the number of breaches increases from 1 to 3, the residual strength ratio decreases progressively, with the rate of decrease accelerating.

Due to its cylindrical configuration and distinctive motion characteristics, the cylindrical FPSO faces significant challenges in offloading operations under complex marine conditions characterized by high-frequency variations in wind, waves, and currents. To address these challenges, particularly under the persistent northeastern and southwestern monsoon conditions in the eastern South China Sea, this study proposes a novel offloading system featuring dual offloading points, bow loading, and position-mooring configuration, intended as a cost-effective alternative to high-cost DP shuttle tankers. The proposed solution integrates a bow thruster on the shuttle tanker and dual stern tugs to enable coordinated control of heading and position, thereby enhancing operational safety and adaptability. To verify the feasibility of the proposed system, a combination of numerical simulations and full-mission maneuvering experiments was conducted. The study systematically investigates key technical aspects such as the selection of shuttle tankers and tugs, bow thruster configuration, and mooring hawser design. Results confirm the feasibility of employing a 75 000 DWT shuttle tanker for position-mooring offloading at the Liuhua oilfield in the South China Sea. Findings indicate a positive correlation between the tension and angle of mooring hawsers and the shuttle tanker's displacement and length. This study provides technical guidance and risk assessment insights for cost-effective offloading operations of cylindrical FPSOs in complex marine environments.

To enhance the bending mechanical properties of fiber-reinforced plastics (FRP) and address rapid damage repair under multiple bending loads, an improved shape memory alloy hybrid composite (ISMAHC) was developed by embedding layered orthogonal shape memory alloy (SMA) wires into FRP. Three-point bending and water bath recovery tests were performed on traditional single-layer unidirectional SMA hybrid composites (SMAHC), ISMAHC and FRP. The effects of layered orthogonal SMA configuration on stiffness, strength, and recovery capability were compared and investigated. Results demonstrate that SMA wires form a coupling effect with FRP, increasing the bending modulus. Furthermore, ISMAHC has higher stiffness due to its orthogonal architecture. The water bath recovery tests indicate that SMAHC and ISMAHC possess good deflection recoverability and mechanical property recoverability after multiple bending loadings. The deflection recovery rate of the first bending test is greater than 60%, and that of the second bending test is greater than 30%. Additionally, the bending modulus and bending strength recover more than 30%, with ISMAHC showing superior recoverability.

To analyze the propagation of pressure waves generated during spherical projectile water entry within liquid-filled structures, this study establishes a computational model for the pressure wave considering reflection from a preset air layer. The model combines the virtual and real mirror methods with potential flow theory, and its accuracy is validated through numerical simulations. Using the established model, the propagation processes of the pressure wave during projectile water entry within liquid-filled structures configured with either a top air layer or a centrally located spherical air layer are examined. The effects of air layer height h, spherical air layer center location D and radius r on the strength and propagation of the pressure wave in water are analyzed. The results show that the rarefaction wave reflected from the air layer interface induces a truncation effect on the pressure wave propagation, significantly reducing the duration of positive pressure and the specific impulse. Moreover, the specific impulse decreases as h and r increase. A smaller D leads to more significant attenuation of the initial pressure wave specific impulse, while a larger D results in more noticeable attenuation of the secondary pressure wave peak and its specific impulse.

Corrosion-fatigue coupling presents significantly greater risks than damage mechanisms in isolation. This review synthesizes recent research advancements in theoretical frameworks, computational simulations, and experimental methodologies, with a focus on the pitting evolution and crack propagation stages. Existing models of pitting morphology are commonly constrained by single-defect assumptions and geometric regularization, which hinder a comprehensive and multidimensional characterization of pits. In the modeling of crack propagation, three primary paradigms have emerged: mechanism-driven models, data-driven models, and hybrid-enhanced models. Among these approaches, physics-informed neural networks demonstrate considerable potential in addressing complex interactions between corrosion and fatigue. A critical issue identified is the empirical oversimplification in pitting characterization, particularly the assumption of geometric regularity, which serves as a key bottleneck in quantifying corrosion-fatigue synergies. To overcome this limitation, there is a need to develop integrated multidimensional quantification methods that incorporate size, shape, irregularity, and statistical distribution. This area represents a pivotal research frontier. Advancements in this field will lead to transformative insights into the fundamental coupling mechanisms and the assessment of structural integrity for engineering systems. Ultimately, this will facilitate the development of highly accurate corrosion-fatigue life prediction models, which are essential for ensuring the safety of infrastructure.

To address the difficulty in self-starting for vertical-axis water turbines with fixed pitch angles and to improve the efficiency of marine energy utilization, a hybrid power generation device was proposed that incorporated a Savonius-type wind rotor to assist in starting the vertical-axis water turbine. Numerical simulations were conducted to investigate the dynamic output characteristics of this integrated device. Firstly, a three-dimensional two-phase flow numerical tank was constructed using Fluent software, and the mesh partitioning scheme was determined by comparing the values of the power output parameters of the device under different mesh densities, and at the same time, the validity of the numerical tank was confirmed. Secondly, the established numerical tank was used to simulate the variation law of torque, speed and power coefficient of power generation devices under different flow field conditions with different water wheel blade numbers, radius ratios and height ratios. The results show that the device performs better in terms of torque stability, speed characteristics, and energy utilization in the simulated working condition range when the water wheel blades are 3 to 4, the radius ratio is 0.25 to 0.375, and the height ratio is 1/6 to 1/3. The device is able to start quickly in the presence of wind, and the power coefficient reaches 0.3 to 0.4 or even exceeds 0.4, with good starting and power generation performance. The research results can provide a reference for the design and application of the device.

This paper investigates the effects of different overload conditions on crack propagation behavior of AH32 steel, including tensile overload ratios, overload-underload, underload-overload and underload. The residual stress distribution in the region near the crack tip under different overload ratios and overload conditions all result from plastic deformation of the material near the crack tip during fatigue crack propagation. It is shown that applying tensile overload postpones the crack growth, while underload promotes the crack growth. Furthermore, it is also observed that the crack closure level shows a fast increase with the increase of overload ratio. Finally, it can be seen that the mechanism of residual stress at the crack tip and the mechanism of plastic deformation at the crack tip controlling the transient crack growth behavior under variable amplitude loading are essentially the same.

The maritime environment and loading conditions encountered by large ore carriers are highly complex. It is a problem worth studying to scientifically describe the uncertain load of ore carriers and evaluate the safety margin of hull beams quantitatively. This paper investigated the stochastic characteristics of environmental loads and ship internal loads and explored methods for combining multiple loads and their nature mechanics. This research also revealed the still-water bending moment characteristics under typical loading conditions. WALCS hydrodynamic analysis software was used to calculate the wave load response function of the target ship. The extreme values of the wave bending moments were obtained using the extreme value type I (Gumbel type I) long-term forecasting method. The statistical characteristics of the wavebending moments were analyzed. Based on the uncertainty load combination method, the hull girder safety margin of the target ship was obtained as 1.10-1.20. The rationality of the load system specified in the CCS rules for ore carriers is further validated. The results show that the method can be applied to the formulation of relevant ore ship rules by CCS and effectively reveal the safety margins behind the rules. Understanding of the GBS-type ship rule has been enhanced. This research provides an important reference for the development of large ore carriers.

Polymer materials are usually applied to the sheath layers on the surface of marine flexible pipes. Such kind of material exhibits certain nonlinear characteristics, specifically manifested as a stress-strain nonlinearity and stress relaxation phenomena. In this paper, specimens are specially designed, and specific testing instruments are used according to relevant international standards to conduct tensile and stress relaxation tests on polymer materials for marine non-bonded pipes under high temperature environments. The tensile stress-strain curve and stress relaxation curve are obtained, and the Prony series constitutive parameters describing their stress relaxation characteristics are then identified from the stress relaxation test data, and verified using finite element method. Finally, the characteristics of stress relaxation in polymer materials are discussed. It is found that there is no pure elastic deformation stage in polymer materials during tensile deformation, and that the coexistence of elastic deformation and plastic deformation is reflected from the beginning of tensile deformation. The essence of stress relaxation phenomenon in polymer materials is the transformation from elastic to plastic deformation of the material. When plastic deformation accounts for the majority of internal deformation of the material, the percentage of stress reduction during the relaxation process will be smaller compared with the case when elastic deformation accounts for the majority. In engineering, if considering to reduce the effects of stress relaxation, polymer materials can be approximately taken as directly entering plastic deformation stage.