Advances in Marine Mechanical and Structural Engineering

In the design of modern ship and offshore structures, one of the key issues is the accurate prediction of strength with regard to various new materials and structures used in the structural design stage and under extreme sea environment and accidental states. The advancements in marine, mechanical and structural engineering are used in the mechanical analyses of advanced materials, such as alloys and composite materials, and strength analyses of novel structures, such as sandwich structures and superstructures, in order to render structures lightweight, safe and economical throughout their lifetimes.

The present Special Issue contains 14 articles, with 4 papers addressing the impact of ship and offshore structures, 2 papers being related to the mechanical behavior of novel structures, 3 papers covering various aspects of the strength assessment of ship and offshore structures, 1 paper being dedicated to vibration control in novel marine equipment, 2 papers regarding the soil–structure interaction analysis of offshore structures, 1 paper dealing with the load identification of ships and 1 paper focusing on the displacement analysis of ship shafting.

The definition of material failure criteria is an issue in the impact analysis of structures. Wang et al. [1] analyzed the deformation characteristics of a common cruciform structure, which is a part of ship hull structures, under planar collision and quasi-static loading. The applicability of the EPS, BWH and RTCL failure criteria in the simulation of compressive structures was investigated via the finite element simulation of quasi-static tests and falling weight impact tests. The effects of mesh size on the deformation and impact force of cruciform structures under plane loading were comparatively analyzed. The results showed that under plane loading, a cruciform structure undergoes axial compression deformation first, followed by buckling and wrinkling deformation. It is worth noting that the RTCL failure criterion is effective in modeling the failure of compressive structures in simulations with structures with different compressive deformations.

The risk of collisions between passing vessels and wind turbines is increasing, representing a serious threat to the safety of personnel and equipment. Zong et al. [2] established a fluid–structure coupling simulation method based on Star-CCM+ and ABAQUS. It was used to investigate the dynamic response of floating wind turbines following bow and side impacts from vessels. A sensitivity analysis was performed on parameters such as collision speed, collision angle, wind speed, and wave height. The findings indicated that the amplitude of pitching and heaving motions of a turbine exceed those observed under conditions devoid of collision loads, with the amplitude of motion intensifying with an increase in these parameters.

A comprehensive understanding of the dynamic behavior of materials and structures under impact loads is paramount for structural design and maintenance. Tian et al. [3] carried out quasi-static and dynamic tensile tests using Q235 steel to obtain its material properties. The acquired data were utilized to fit the parameters using the Johnson–Cook model, a widely accepted constitutive model employed in high-strain-rate applications. The tensile test was numerically simulated based on the acquired experimental parameters. The good agreement between the load–displacement curves of the tests and simulations provided robust validation of the accuracy of the dynamic mechanical parameters of Q235 steel.

The phenomenon of repeated impacts on engineering structures is very common, especially in ocean engineering. Guo et al. [4] established a theoretical model based on the rigid–plastic assumption in order to analyze the plastic mechanical behavior of metal foam sandwich beams suffering from repeated impacts. The theoretical predictions agreed well with the results of impact tests and numerical simulations, indicating that the theoretical model was accurate and reliable. The results showed that the dimensionless permanent deflection was sensitive to the core strength ratio and the face thickness ratio, and as the core strength ratio or the face thickness ratio increased, the dimensionless permanent deflection decreased gradually in an exponential form.

A honeycomb structure is one of the most representative advanced structures in recent investigations. Wang et al. [5] analyzed the effect of nodal configuration on the mechanical properties of honeycombs. Several quasi-static compression tests were performed, which revealed that nodal reinforcement can inhibit nodal aberrations during ligament winding, thus facilitating the “rotational” mechanism and improving the negative Poisson’s ratio properties of the honeycomb. Experimental and finite-element analyses showed that nodal reinforcement mainly played a role in the stage in which stress increased, and the role of nodal filling was more significant than that of nodal thickening. Li et al. [6] analyzed the mechanical performance of an improved star-shaped honeycomb. A quasi-static compression test was carried out to investigate its deformation mode and mechanical properties. To further utilize the excellent performance of the structure and obtain a better negative Poisson’s ratio effect and broader application, a three-dimensional improved star-shaped honeycomb structure was proposed and a finite element simulation was carried out. The effects of the structural design, materials and dimensions on the mechanical properties, such as the energy absorption and negative Poisson’s ratio, of the structures were explored.

Global ship analysis involving structural, motion and vibration analyses are crucial to examine the structural safety of hulls and motion response in ship design and construction. Lim et al. [7] performed finite element analysis, and weight distribution was employed to make the weight lighter and adjust the center of gravity. An effective and accurate algorithm and program was proposed to tune the weight, longitudinal shear force, bending moment and center of gravity of the ship finite element model to the required target value. The accuracy of the newly developed algorithm was analyzed and compared by applying it to the shuttle tanker finite element model under the ballast and full load conditions.

Ship bows and stems are often subjected to wave slamming loads. Stiffened plates with curvatures in both longitudinal and transversal directions are the basic components of these structures. Guo et al. [8] investigated the lateral ultimate strength of doubly curved stiffened plates using the non-linear finite element method. An empirical formula was derived and verified for the prediction of the lateral ultimate strength of the doubly curved stiffened plates, having good agreement with the numerical calculations.

A bolted ball joint structure has been utilized in offshore floating platforms and deep-sea fish cages, and Du et al. [9] presented an innovative method to improve the sealing performance of bolted ball joints. The approach involved creating sealed surfaces within the contact gaps between sleeves and connecting components by adding circular grooves and sealing washers to both ends of the sleeve.

The analysis of the interaction between pipes and sandy soil is of importance in the design of submarine oil and gas pipelines. Wang et al. [10] carried out experiments to study pipe–soil interaction, specifically measuring the lateral soil resistance of flexible pipes at varying burial depths. To simulate the mechanical behavior of pipe–soil interaction, the coupled Eulerian–Lagrangian method was employed for numerical simulations. The research findings indicated that lateral soil resistance is influenced by the uplift height and accumulation width of the soil ahead of the pipe. The ultimate soil resistance exhibited an increasing trend with an increasing burial depth.

Submarine cable burial machines are used for trenching operations on the seabed. Yu et al. [11] proposed a novel mechanical burial machine design employing a chain-type structure based on a combination of theoretical considerations and practical requirements. Through theoretical analysis, simulation and experimental studies, the cutting process of the mechanical burial machine was investigated in detail, with special attention given to the seabed conditions in the Northeast Asia region.

A pendulum-tuned mass damper is a widely used vibration-damping device capable of transferring and dissipating structural vibration energy. Du et al. [12] investigated the application and design of a pendulum-tuned mass damper in a buoyancy platform and analyzed its vibration reduction performance. Finite-volume simulations of the structure were conducted, providing insights into its motion under flow field effects and validating the damper’s effectiveness in mitigating the buoyancy platform’s flow-induced vibrations.

The identification of longitudinal bending moments is a critical component in the health monitoring of ship structures. Xu et al. [13] examined the effect of the failure of measurement points on the accuracy of bending moment identification and presented a solution method. The impact of failure point position and quantity on strain fitting accuracy and bending moment identification was investigated by performing a four-point bending experiment in typical failure scenarios. Further numerical analysis was conducted to identify potential sources of errors in the measurement process.

Deviations between the design and actual shafting occur due to limitations in ship construction accuracy. It is challenging to accurately obtain the relationship between the actual shafting load and displacement relationship based on the shafting design. To address the issue of incomplete actual shafting data, Deng et al. [14] proposed a transfer learning-based method for the accurate calculation of bearing displacement values. By combining simulated data from the shafting design with measured data generated during the adjustment process of the actual shafting, higher accuracy could be achieved when calculating bearing displacement values.

In summary, the articles presented in this Special Issue cover broad research topics related to advancements in marine mechanical and structural engineering, guiding readers through the best approaches to analysis.