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[Objectives] Sandwich plate system(SPS)has superior impact resistance and can be used in a design for the partial strengthening of a bow to improve its anti-slamming performance.[Methods] Nonlinear finite element software LS-DYNA is used to analyze the structural energy absorption and stress of the SPS-clad bow under slamming loads,designed according to the principle of mass equivalence. The energy absorption characteristics of the SPS-clad bow are then compared with those of a traditional steel bow.[Results] The results show that the peak specific energy absorption of the SPS-clad bow is 18.2% higher than that of the steel bow;the outer panel of the SPS cladding is the main energy absorption component of the bow,and the increase in the peak specific energy absorption of the SPS cladding of the bow is 41.3% higher than that of the steel bow;the peak stress of the inner panel of the SPS-clad bow is smaller.[Conclusions] The application of SPS cladding for the partial strengthening of a bow can significantly improve the energy absorption effect of the structure,buffer slamming loads,reduce internal structural stress and ensure structural safety. It is an effective means of improving the overall ultimate bearing capacity of a bow under slamming conditions. These research results can provide references for the design and manufacture of high-performance ships.

With deep-learning-based object detection methods reaching industrial-level performance, underwater object detection has emerged as a significant application. However, it is often challenged by dense small instances and image blurring due to the water medium. In this paper, a Multi-Scale Feature Enhancement(MSFE) method is presented to address the challenges triggered by water bodies. In brief, MSFE attempts to achieve dual multi-scale information integration through the internal structural design of the basic C2F module in the Backbone network and the external global design of the feature pyramid network (FPN). For the internal multi-scale implementation, a LABNK module is constructed to address the vanishing or weakening phenomenon of fine-grained features during feature extraction. Specifically, it adopts a symmetrical structure to collaboratively capture two types of local receptive field information. Furthermore, to enhance the information integration ability between inter-layer features in FPN, a shallow feature branch is injected to supplement detailed features for the subsequent integration of multi-scale features. This operation is mainly supported by the fact that large-sized features from the shallow layer usually carry rich, fine-grained information. Taking the typical YOLOv8n as the benchmark model, extensive experimental comparisons on public underwater datasets (DUO and RUOD) demonstrated the effectiveness of the presented MSFE method. For example, taking the rigorous mAP (50:95) as an evaluation metric, it can achieve an accuracy improvement of about 2.8%. [ABSTRACT FROM AUTHOR]

Unlike uncertainties stemming from loads and material properties, interface uncertainties arising from variations in immersed media within the acoustic field can significantly alter the solution domain, leading to substantial dispersion in radiated acoustic pressure. To address this issue, this study introduces the extended finite element method (XFEM), Dirichlet-to-Neumann (DtN), and direct probabilistic integration method to develop a two-dimensional stochastic acoustic radiation analysis approach for systems with immersed media interface uncertainties. The XFEM with DtN enables accurate capture of the non-smooth solutions at the interface by constructing enriched functions without modifying the original mesh and allows the introduction of random parameters to describe the interface modifications. The input probability space of the parameters is partitioned and the Dirac δ function is smoothed, and the statistical properties such as the probability density function of system responses are obtained by summing the response under each representative point, which can efficiently treat the propagation of interface uncertainties. The computational performance of the proposed scheme is validated using examples of infinite oscillating rigid cylinders and submarine acoustic radiation. Furthermore, the impact of parameters such as the position and thickness of porous material domains on the radiated acoustic pressure is discussed. [ABSTRACT FROM AUTHOR]

Aiming to address the multi-objective cooperative optimization problem of ship structure lightweight and crashed-resistance, this study proposed a concave reentrant honeycomb-based negative Poisson's ratio (NPR) sandwich structure to replace the stiffened plate. The feasibility of using the sandwich structure to improve ship crashworthiness is demonstrated through finite element analysis. An intelligent optimization method is established to address the issues of multiple parameters and complex effects associated with composite structures and optimize the crashworthiness of the sandwich structure. The effectiveness of the optimization method and the feasibility of the NPR sandwich structure in ship crashworthiness have been validated, providing a reference for the design of new multi-functional ship structures. [ABSTRACT FROM AUTHOR]

To predict the anti-penetration performance of protective structures, the ballistic performance of sandwich plates with steel face-sheet and aluminum foam core, the quasi-static compressive experiments of four different aluminum foam are performed and analyzed. The failure mechanism, mechanical parameters, and modified constitutive model are obtained. The virtual tests using numerical simulation were carried out in different penetration velocities based on quasi-static experimental constitutive parameters. Influence of projectile shape, face-sheet thickness, core thickness, and core densities on the residual velocity and plastic deformation of sandwich plates are discussed, while typical penetration failure modes and deformation mechanism are presented and analyzed. The failure modes of sandwich plates are different for hemisphere- and blunted-nosed projectile and the projectile shape influence is significant for ballistic performance when the penetration velocity approaches ballistic limit. The ballistic limit increases with increase of face-sheet or core thickness, core density and which shows an approximate linear relationship. [ABSTRACT FROM AUTHOR]

A new kind of higher order analysis model is presented for sandwich plates with flexible core, especially “soft” core. The governing equations derived from equilibrium differential equations of motions are analytically solved for simply supported sandwich plate with a flexible core. The Navier-type solutions for free vibration analysis and static bending are presented for sinusoidal and uniformly distributed loads. The accuracy and convergence of the present theory and solution are ascertained by comparing with various available results, the author considered vary of length-to-width ratios, Young’s modulus ratios between skins and core, thickness ratios between skins and core, and span-to-thickness of sandwich plates. The results show that the present theory can achieve the great accuracy for sandwich plate with flexible core by comparing with existing classical plate theory, first-order shear deformation, higher order shear deformation theory, and finite element software ANSYS. [ABSTRACT FROM AUTHOR]