In this paper, the dynamic response of continually density-graded aluminum foam sandwich tubes under internal explosion load was studied. A 3D mesoscopic finite-element model of continually density-graded aluminum foam sandwich tubes was established by the 3D-Voronoi technology. The finite-element results were compared with the existing experimental results, and the rationality of the model was verified. The influences of the core density distribution, the core density gradient, and the core thickness on the blast resistance of the sandwich tubes were analyzed. The results showed that the blast resistance of the sandwich tube with the negative-gradient core is better than that of the sandwich tube with the uniform core. While the blast resistance of the sandwich tube with the positive-gradient core or the middle-hard-gradient core is worse than that of the sandwich tube with the uniform core. For the sandwich tube with the negative-gradient core, the core density gradient increased, and the blast resistance decreased. Increasing the thickness of the core can effectively decrease the deformation of the outer tube of the sandwich tube, but the specific energy absorption of both the whole sandwich tube and its core also decreases.

In this paper, low-velocity impact of square columns filled with density-graded foam (DGF) is investigated experimentally, numerically and analytically. The low-velocity impact experiments are carried out to study the effect of density gradient on the deformation patterns and energy absorption of the DGF-filled columns. Numerical calculations are performed to study the effects of density distribution mode, density difference, average density of DGF and wall thickness of square column on the energy absorption. According to the energy method and basic folding element theory, the instantaneous dynamic crushing force is predicted analytically. The analytical predications are in good agreement with experimental results. It is found that the DGF-filled columns have excellent energy absorption capacity and low initial peak force compared to the uniform-filled columns with the same weight.

In this paper, we numerically investigate the dynamic response and explosion resistance of gradient aluminum foam sandwich tubes subjected to external blast loads. Based on 3D-Voronoi technology, we construct density-graded aluminum foam cores to systematically explore the influence of core density distribution, density gradient, and average relative density on the protective performance of these structures. Our primary objective is to identify optimal design parameters that maximize explosion mitigation capabilities while balancing energy absorption and specific energy absorption capacities. The research results show that a positive gradient core configuration exhibits superior anti-explosion performance, significantly outperforming its uniform and negatively graded counterparts, particularly when the gradient value is substantial. For the positive gradient cores, an increase in the gradient value leads to a corresponding enhancement in explosion resistance. Conversely, in negatively graded cores, a higher gradient value diminishes the anti-explosion performance. Furthermore, while augmenting the relative density of the core layer does improve the overall explosion resistance of the sandwich tube, it comes at the cost of reduced energy absorption and specific energy absorption capabilities, highlighting the need for a delicate balance among these competing factors.

The objective of this work is to investigate dynamic response of fully clamped slender foam-filled rectangular tubes subjected to low-velocity impact. Analytical and numerical analysis are presented to predict the dynamic response of the fully clamped slender foam-filled rectangular tubes struck by a low-velocity heavy mass. In the analytical solutions, the interaction of bending and stretching induced by large deflections is considered. Good agreement is achieved between the analytical solutions and numerical results. It is shown that the filled foam strength has significant effect on the impact resistance capacity of foam-filled tubes.

This work focuses on investigation of the internal blast resistance of metal sandwich tubes with continuously radial density-graded aluminum foam cores. Based on the 3D-Voronoi technology in polar coordinates, unidirectionally and bidirectionally continuously density-graded aluminum foam were developed for the cores of sandwich tubes in Finite Element (FE) model. And the correctness of core gradient was verified by comparing theoretical design with the actual value generated by FE model. Effects of core density distribution and core density gradient on blast resistance of sandwich tubes were explored and identified. The results indicate that, when the core density gradient is constant, the sandwich tube with negative-gradient core exhibits the smallest maximum deformation of the outer tube, while the negative-middle-low-gradient core tube shows the highest specific energy absorption ( SEA). For negative-gradient core tube, as the core density gradient increases, the maximum deformation of the outer tube decreases significantly, with only slight reduction of the structural SEA. For negative-middle-low-gradient core tube, as the core density gradient increases, the maximum deformation of the outer tube decreases, while the SEA increases.

To reveal the electromagnetic response characteristics and hydro-thermal evolution mechanism of frozen soil under microwave irradiation, we used remolded frozen soil prepared from undisturbed parent soil collected in Hegang, China, as the research object. We conducted dielectric parameter tests across the 715–1150 MHz and 2250–2650 MHz frequency bands and 1.5 kW microwave heating tests on specimens with three gravimetric water contents (15%, 20%, and 25%) paired with a coupled numerical simulation of electromagnetic field-heat transfer-moisture migration. The results show that water content is the dominant factor controlling the dielectric response of frozen soil. The dielectric loss and water content sensitivity of frozen soil in the low-frequency band (dominated by unfrozen water) are significantly higher than those in the high-frequency band (dominated by ice phase and soil matrix). Microwave-induced temperature rise exhibits a three-stage characteristic, as follows: slow temperature rise, isothermal plateau at the freezing point, and rapid temperature rise. Specimens with a lower initial water content show a higher temperature rise efficiency in the late heating stage, with a maximum rate of 1.112 °C·s⁻¹ for the 15% water content specimen. Mass loss is negatively correlated with initial water content, with a maximum value of 1.8 g after 120 s of irradiation. In addition, the non-uniformity of the electromagnetic field results in a temperature field pattern characterized by a high-temperature core at the specimen center and lower temperatures at the edges. This study provides fundamental theoretical support and technical guidance for the application of microwave thawing technology in geotechnical engineering, particularly for frozen soil foundation treatment in cold regions.