The effects of pre-compression and pre-aging on the age-hardening response and microstructure of Mg-9.8Sn-3.0Zn (wt.%) alloy have been investigated via hardness test and advanced electron microscopy. The alloy subjected to both pre-compression and pre-aging exhibits the most refined and densest distribution of precipitates upon aging at 200 °C, leading to the superior age-hardening performance observed in the alloy. Comparatively, the alloy that underwent only pre-aging displayed a greater number density of precipitates than its counterpart that was neither pre-compressed nor pre-aged when both were aged to their peak conditions at 200 °C, indicating an enhanced age-hardening response in the pre-aged alloy. The precipitates in these three peak-aged alloys consist of Mg₂Sn and MgZn₂ phases. The reason why the pre-aged alloy has a higher number density of precipitates than the directly aged alloy is that MgZn₂ phase formed during pre-aging can serve as heterogeneous nucleation site for the formation of Mg₂Sn. The reason why the pre-compression and pre-aged alloy has the highest number density of precipitates is that Mg₃Sn and MgZn₂ phases formed during pre-aging, alongside lattice defects introduced during pre-compression, collectively act as effective heterogeneous nucleation sites for the formation of Mg₂Sn during the subsequent aging at 200 °C.

Improving interfacial bonding and alloying design are effective strategies for enhancing mechanical properties of particle-reinforced steel matrix composites (SMCs). This study prepared SMCs with uniformly distributed TiC_P in matrix using master alloying method. The TiC(002)/Fe(011) interface model was established based on the orientation relationship of (011)_Fe//(002)_TiC, and [100]_Fe//[100]_TiC. The effects of single and co-doping of alloying elements (Mn, Cr, Mo, Ni, Cu and Si) on the interface bonding behavior of TiC/Fe in composites were investigated in conjunction with first-principles. The results demonstrate that the interface between TiC and matrix is continuous and stable. Compared to the undoped TiC/Fe interface, single-doping Mn, Cr, and Mo can improve the stability of TiC/Fe interface and enhance tensile strength. Conversely, single-doping with Ni, Cu, and Si reduced the interface stability and marginally reduces tensile strength. Relative to the undoped and singly Ni-doped TiC/Fe interfaces, the co-doping Ni-Mo boosts binding energy and separation work at the TiC/Fe interface, which is conducive to the interface bonding between TiC_P and matrix, and thus improves the mechanical properties of composites. Thus, in the alloying design of TiC particle-reinforced low-alloy SMCs, incorporating Mn, Cr, Mo, and Ni into matrix can enhance the overall mechanical properties of composites.

Microstructure and mechanical properties of aged Mg-10Gd-2Y-0.4Zr-0.4Ag alloy sheets prepared by different rolling routes were investigated. The results showed that the cross rolling aged (CRA) sheet possesses larger grain size than unidirectional rolling aged (URA) sheet due to the occurrence of dynamic recovery during rolling which reduces the dislocation density and delays dynamic recrystallization (DRX). The URA sheet has basal texture and RD-favored texture while CRA sheet has multiple-peak texture. Both sheets precipitate β′ phase and CRA sheet exhibits a stronger aging response. The CRA sheet has higher yield strength and tensile strength than URA sheet, with reduced yield strength anisotropy but increased tensile strength anisotropy. Taking into account different strengthening mechanisms, although the finer grain size of URA sheet enhances grain boundary strengthening, CRA sheet is more responsive to aging, leading to superior aging-precipitated phase strengthening and consequently higher yield strength.

In this work, tensile mechanical behavior of 316L steels fabricated by three different processing methods (casting, powder extrusion printing (PEP) and laser powder bed fusion (LPBF)) was studied in the presence of liquid lead-bismuth eutectic (LBE) and air at 350 °C. The results show that all three steels tested in LBE are not subjected to evident degradation of tensile elongation to failure and strength compared to those tested in air, suggesting that LME does not occur regardless of the processing methods. The LPBF 316L steel exhibits the highest yield strength (420–435 MPa), followed by casting 316L (∼242 MPa) and PEP 316L (146–165 MPa). Ultimate tensile strength of three steels is comparable and ranges from 427 to 485 MPa. The PEP and casting 316L steels have similar total elongation to failure (i.e., 40.0%–43.8%), whereas this property decreases markedly to 18.6%–19.5% for the LPBF 316L steel. The superior strength and relatively low ductility of the LPBF 316L steel can be attributed to nanosized dislocations trapped at cell structures which can produce a remarkable strengthening effect to the steel matrix. By contrast, due to massive residual micropores, the PEP 316L steel has the lowest strength.

The microstructure, fracture mechanisms, deformation modes, and their correlation with the mechanical properties of Mg-Zn-Gd alloys were analyzed, considering the influence of Y and Nd additions. Increasing Y content and decreasing Nd content resulted in an increase in grain size from 17.2 to 29.2 jim, and two types of LPSO phases, 14H and 18R, formed in the alloy. The mechanical properties of the alloys were predominantly influenced by the LPSO phase, with the grain size effect being relatively minor. Based on this analysis, higher Y and lower Nd contents enhanced the tensile strength, yield strength, and elongation of the alloys, with additional improvements observed following solid solution treatment. Changes in Y and Nd content caused a shift in fracture patterns, transitioning from ductile fracture to brittle fracture and then to mixed fracture. Following solid solution treatment, the alloy progressively transitions from intergranular to a combination of ductile and deconvolutional fracture. The deformation modes observed at each stage are as follows: an increase in LPSO phases and twins activates pyramidal slip and suppresses prismatic slip.

CaO-based heat carriers have shown great prospects for thermochemical energy storage in concentrated solar power systems due to the features such as rich reserves, environmental safety, high energy storage densities and high operation temperatures. However, the density decay because of sintering and poor direct solar absorption of white CaO-based heat carriers are the two main obstacles lying on the way to the realistic applications. This work introduced dark Mn-based inert support into calcium heat carriers, attempting to solve the above problems simultaneously. As an inert support, the finely dispersed Ca₂MnO₄ functioned as the metal framework to resist CaCO₃/CaO sintering. Consequently, the cyclic stability of CaO-based heat carriers, resulting in the high energy storage densities of ∼2000 kJ/kg even over 20 cycles. As a dark material, Ca₂MnO₄ successfully darkened CaO-based heat carriers, thereby greatly enhanced the direct solar absorption. In addition, the granulation of CaO-based heat carriers was also studied. The pellets showed satisfactory attrition resistance with only 9.85 wt% mass loss over 3200 cycles. In general, good physicochemical performance of Mn-doped CaO-based heat carrier endows it with great prospects for solar energy storage.

To accurately identify the factors affecting the formation of stable aggregates in bauxite residue during the soil-formation process, the comprehensive effects of a combined chemical-biological amelioration strategy including solid wastes and a functional microorganism on aggregate size distribution and its stability in bauxite residue were investigated during a 365-d simulation experiment. The results showed that the combined amelioration effectively reduced the saline-alkalinity of bauxite residue, and markedly changed the contents of aggregate-associated chemical binding agents. Desulfurization gypsum and maize straw-Penicillium oxalicum (P. oxalicum) differentiated the formation of aggregates within different sizes. Maize straw-P. oxalicum stimulated the formation of water-stable macroaggregates with more durable erosion resistance by the wet-sieving and laser dynamic diffraction analysis. The Pearson correlation analysis showed that exchangeable polyvalent metal ions, pyrophosphate extractable Fe oxide, and organic carbon exhibited positive correlations with aggregate stability during the 365-d incubation. The findings in this study may provide data support and engineering practical reference for ecological restoration in the disposal areas.

The phase transformation of galena in H₂SO₄–Fe₂(SO₄)₃ system under oxygen pressure was investigated. Results indicated that the critical conditions for the phase transformation of galena into lead jarosite (Pb-J) were 130 °C, 30 g/L H₂SO₄, 15 g/L Fe³⁺, and an oxygen partial pressure of 0.4 MPa. Furthermore, increased Fe³⁺ concentration and oxygen partial pressure did not enhance jarosite formation. Conversely, lowering the temperature and increasing the H₂SO₄ concentration facilitated PbSO₄ formation and inhibited its further conversion to Pb-J. Additionally, the effects of potassium sulfate, sodium sulfate, and high concentrations of zinc sulfate on the phase transformation of galena were examined through leaching tests, XRD, SEM-EDS, and FT-IR analyses. All three sulfates inhibited the conversion of galena to Pb-J. Among these, potassium sulfate prevented Pb-J formation and converted it more thoroughly into potassium jarosite. However, high concentrations of zinc sulfate facilitated the crystallization of both PbSO₄ and Pb-J, which altered the morphology of the product. Zinc ions coprecipitated with Pb-J, thereby integrating into the product.

Flotation behavior of stibiconite after sulfidation roasting with sulfur at a high temperature and the sulfidation mechanisms were investigated by ultraviolet spectrophotometry, X-ray diffraction (XRD) combining with thermodynamic calculation, X-ray photoelectron spectroscopy (XPS) and electron probe microanalysis (EPMA). The XRD and thermodynamic analyses revealed that the Sb₃O₆(OH) was reduced into Sb₂O₄ and Sb₂O₃, and was transformed into Sb₂S₃ after introducing sulfur at high temperatures. Flotation test results show that flotation recovery of the stibiconite after sulfidation reaches 90.3%. Ultraviolet spectrophotometry tests confirm that adsorption capacity of sodium butyl xanthate (SBX) on surface of the roasted products has a positive relationship with S/Sb mole ratio. XPS analyses indicate that Sb-bearing species including mainly Sb₂S₃, Sb₂O₃ and Sb₂(SO₄)₃ are formed at the surface of particle after sulfidation. The EPMA analyses verify that the Sb₂S₃ is generated at the outer layer of sample after sulfidation roasting, but the particle interior is mainly composed of antimony oxides. The sulfur atmosphere induces the outward migration of oxygen to form Sb₂O₄. Then, the Sb₂O₄ is transformed into Sb₂O₃ in two pathways, and the Sb₂S₃ is formed. These findings will provide theoretical support for recovering antimony from antimony oxide ores by xanthate-flotation methods.

Roasting bastnaesite concentrates is a crucial process in extracting rare earths. This study explored an efficient suspension roasting technology and investigated the bastnaesite pyrolysis and cerium (Ce) oxidation. Relevant analytical tests were applied to evaluate the phase and surface property variations of bastnaesite, and isothermal kinetic analysis of bastnaesite pyrolysis and Ce oxidation was performed. The results revealed that bastnaesite decomposed rapidly and accompanied by Ce oxidation, and the gas-solid products were identified as CO₂, Ce₇O₁₂, La₂O₃, CeF₃ and LaF₃, with Ce oxidation restricted by bastnaesite pyrolysis. As roasting time prolonged, cracks and pores appeared on bastnaesite surface; the BET specific surface and pore diameter increased. In later roasting period, the pore diameter continued to increase but the specific surface decreased, assigned to particle fusion agglomeration and pore consolidation. Additionally, the surface C content reduced and Ce(IV) content increased gradually as roasting progressed. The reaction kinetics all followed Avrami-Erofeev equations, the reaction orders of bastnaesite pyrolysis and Ce oxidation decreased with decreasing reaction temperature. The calculated activation energies at lower temperatures were higher than those calculated at higher temperatures. This study analyzed the bastnaesite reaction mechanism to supply a reference for the application of suspension roasting technology in bastnaesite smelting.

In this study, a synergistic sulfidation-acid leaching process was proposed to recover valuable metals from gypsum residue and zinc-containing fume. The equilibrium phase composition of the sulfidation reaction and calculations of the thermodynamic stability region show that 89.36% Zn, >99% Pb and >99% Cu of gypsum residue and zinc-containing fume can be sulfured to ZnS, PbS and Cu₂S, under sufficient sulfur partial pressure, low oxygen partial pressure and 400–1000 °C. Sulfidation roasting experiments show that the sulfidation rate of Cu, Pb and Zn reach 81.43%, 88.25% and 92.31%, respectively, under the roasting conditions of material mass ratio of 30 g: 10 g, carbon dosage of 3.75 g, roasting temperature of 800 °C for 3 h. E–pH plots show that ZnS, PbS and Cu₂S can be enriched in the leaching residue, under leaching conditions at 25 °C, pH<4 and −0.4 V<φ(E)<0.04 V. The leaching experiments showed that the sulfide is retained in the leaching residue, while the leaching rates of Cu, Pb and Zn are 1.94%, 2.05% and 1.51%, respectively, under the conditions of 25 °C, C_HCl of 0.5 mol/L, L/S of 5 mL/g, stirring rate of 300 r/min, and stirring time of 30 min. This study provides a new approach for the synergistic disposal of gypsum residue and zinc-containing fume.

At present, the surrounding rock of the deep mine roadway is prone to post-peak stress under the action of high stress, and secondary rock burst disaster is prone to occur under complex stress disturbance. According to incomplete statistics, as of 2023, 80% of coal mine rock bursts accidents in China occur in mining roadway. In view of this phenomenon, the cyclic impact test of post-peak sandstone is designed, focusing on the post-peak stress state of sandstone, and exploring the post-peak dynamic response of sandstone. The post-peak sandstone specimens were prepared by a uniaxial compressor, and then cyclic impact tests were carried out on the post-peak sandstone under different coaxial pressure conditions by an improved separated Hopkinson equipment. The results show that: 1) The number of impact times required for sandstone failure after peak decreased with the increase of axial pressure, indicating that the impact tendency of sandstone after peak decreased under lower axial pressure. On the contrary, the post-peak sandstone had strong impact tendency under higher axial pressure; 2) The higher the axial pressure, the lower the dynamic strength of the post-peak sandstone, indicating that the axial pressure promoted the failure process of the post-peak sandstone; 3) It was a nonlinear evolution of a quadratic polynomial function between the dissipation-energy release rate and axial pressure; 4) Shear failure occurred mainly in post-peak impact sandstone with the increased axial pressure, and the composite failure of intergranular failure and transgranular failure changed to single intergranular failure at the microscopic level. The research shows that when the roadway surrounding rock was in the post-peak stress state, reducing the static stress was the key to prevent the secondary ground pressure disaster. The research results provide a theoretical basis for the prevention and control of roadway rock burst disaster under high ground stress environment, and promote the research and exploration of post-peak mechanical properties of coal and rock.

Cemented tailings backfill (CTB) is a crucial support material for ensuring the long-term stability of underground goafs. A comprehensive understanding of its compressive mechanical behavior is essential for improving engineering safety. Although extensive studies have been conducted on the uniaxial compressive properties of CTB, damage constitutive models that effectively capture its damage evolution process remain underdeveloped, and its failure mechanisms are not yet fully clarified. To address these gaps, this study conducted systematic uniaxial compression tests on CTB specimens prepared with varying cement-tailings ratios. The results revealed distinct compaction and softening phases in the stress – strain curves. A lower cement-to-tailings ratio significantly reduced the strength and deformation resistance of CTB, along with a decrease in elastic energy accumulation at peak stress and dissipation energy in the post-peak stage. Based on these findings, a modified damage constitutive model was developed by introducing a correction factor, enabling accurate simulation of the entire uniaxial compression process of CTB with different cement-tailings ratios. Comparative analysis with classical constitutive models validated the proposed model’s accuracy and applicability in describing the compressive behavior of CTB. Furthermore, particle size distribution and acoustic emission tests were employed to investigate the influence of cement-tailings ratio on failure mechanisms. The results indicated that a lower cement-tailings ratio leads to coarser particle sizes, which intensify shear-related acoustic emission signals and ultimately result in more pronounced macroscopic shear failure. This study provides theoretical support and practical guidance for the optimal design of CTB mix ratios.

The shear performance of bolts plays a crucial role in controlling rock mass stability, and the roughness of the joint surface is one of the main factors affecting the mechanical properties of anchored joints. The 2nd generation of negative Poisson ratio (2G-NPR) bolt is a new independently developed material characterized by high strength and toughness. However, the influence of joint surface roughness on its anchorage shear performance remains unexplored. This study involves preparing regular saw-tooth jointed rock masses and conducting laboratory shear comparison tests on unbolted samples, 2G-NPR bolts, and Q235 steel anchors. A three-dimensional finite element method, developed by the author, was employed for numerical simulations to analyze the influence of saw-tooth angles on the shear resistance of anchored bolts. The findings show that the anchorage of bolts enhances the shear strength and deformation of saw-tooth rock joints. The 2G-NPR bolts demonstrate superior performance in shear strength and deformation enhancement compared to Q235 steel anchors, including improved toughening and crack-arresting effects. Furthermore, the improvement of the shear strength and displacement of the bolt decreases with the increase of the joint saw-tooth angle. These findings provide a valuable test basis for the engineering application of 2G-NPR bolts in rock mass stabilization.

The study aims to investigate the carbonated water erosion mechanism of lining concrete in tunnels traversing karst environment and enhance its resistance. In this study, dynamic carbonated water erosion was simulated to assess erosion depth, microstructure, phase migrations, and pore structure in various tunnel lining cement-based materials. Additionally, Ca²⁺ leaching was analyzed, and impact of Ca/Si molar ratio in hydration products on erosion resistance was discussed by thermodynamic calculations. The results indicate that carbonated water erosion caused rough and porous surface on specimens, with reduced portlandite and CaCO₃ content, increased porosity, and an enlargement of pore size. The thermodynamic calculations indicate that the erosion is spontaneous, driven by physical dissolution and chemical reactions dominated by Gibbs free energy. And the erosion reactions proceed more spontaneously and extensively when Ca/Si molar ratio in hydration products was higher. Therefore, cement-based materials with higher portlandite content exhibit weaker erosion resistance. Model-building concrete, with C-S-H gel and portlandite as primary hydration products, has greater erosion susceptibility than shotcrete with ettringite as main hydration product. Moreover, adding silicon-rich mineral admixtures can enhance the erosion resistance. This research offers theory and tech insights to boost cement-based material resistance against carbonated water erosion in karst tunnel engineering.

Analyzing the fatigue damage characteristics of hot dry rock (HDR) affected by seawater thermal shock cycles is required for the efficient exploitation of HDR and the conservation of freshwater resources. Mechanical and acoustic emission (AE) monitoring tests were conducted during the triaxial compression of HDR at different confining pressures, temperatures, and numbers of seawater thermal shocks to investigate the seawater damage of HDR. The test results indicated an increase in the cumulative AE counts with increasing temperature and number of seawater thermal shocks, and a decrease in AE counts with increasing confining pressure. The effect of the number of seawater thermal shocks was significant. The AE counts were 276% higher at 15 than at 0 seawater thermal shocks. The b-value increased with the number of thermal shocks and stabilized after 5 shocks. Most of the damage was small fractures, which reduced the rock’s damage resistance. The AE time series under HDR triaxial compression exhibited multifractal features. High-energy AE events dominated the damage mechanism of HDR, indicating shear damage to the HDR. Therefore, this study can provide a reference for seawater as a heat transfer fluid in the design of geothermal energy resource extraction.

Bauxite tailing (BT) slurry has been generated and accumulated in large quantities, posing a threat to the green and sustainable development of the alumina industry. The regression equation between the actual water content and mud-water separation rate was established to achieve efficient resource utilization, and the feasibility of foam lightweight soil (FLS) prepared from BT was investigated. The effects of industrial waste residues (fly ash and slag powder) on the properties of FLS were studied. Meanwhile, the micro-mechanisms were revealed by XRD, SEM-EDS, and TG-DSC. The results revealed that fly ash reduced the workability and compressive strength of FLS. Slag powder can significantly enhance the compressive strength of FLS, which increased by 18.60%–23.26%, 17.07%–58.54% and 12.12%–52.12%, respectively. Besides, slag powder can improve the long-term water stability performance and enhance carbonation resistance. XRD and thermal analyses showed that adding fly ash decreased the hydration degree of FLS, leading to a decrease in the hydration products. Slag powder improved the pore structure and compacted the skeleton structure of FLS. This study would provide an effective way to realize the resource utilization of BT, fly ash, and slag powder, with certain socio-economic and environmental benefits.

This study proposed a new and more flexible S-shaped rock damage evolution model from a phenomenological perspective based on an improved Logistic function to describe the characteristics of the rock strain softening and damage process. Simultaneously, it established a constitutive model capable of describing the entire process of rock pre-peak compaction and post-peak strain softening deformation, considering the nonlinear effects of the initial compaction stage of rocks, combined with damage mechanics theory and effective medium theory. In addition, this research verified the rationality of the constructed damage constitutive model using results from uniaxial and conventional triaxial compression tests on Miluo granite, yellow sandstone, mudstone, and glutenite. The results indicate that based on the improved Logistic function, the theoretical damage model accurately describes the entire evolution of damage characteristics during rock compression deformation, from maintenance through gradual onset, accelerated development to deceleration and termination, in a simple and unified expression. At the same time, the constructed constitutive model can accurately simulate the stress–strain process of different rock types under uniaxial and conventional triaxial compression, and the theoretical model curve closely aligns with experimental data. Compared to existing constitutive models, the proposed model has significant advantages. The damage model parameters a, r and β have clear physical meanings and interact competitively, where the three parameters collectively determine the shape of the theoretical stress-strain curve.

During underground excavation, the surrounding rock mass is subjected to complex cyclic stress, significantly impacting its long-term stability, especially under varying water content conditions where this effect is amplified. However, research on the mechanical response mechanisms of surrounding rock mass under such conditions remains inadequate. This study utilized acoustic emission (AE) and resistivity testing to monitor rock fracture changes, revealing the rock’s damage state and characterizing the damage evolution process during uniaxial cyclic loading and unloading. First, a damage variable equation was established based on AE and resistivity parameters, leading to the derivation of a corresponding damage constitutive equation. Uniaxial cyclic loading and unloading tests were then conducted on sandstone samples with varying water contents, continuously monitoring AE signals and resistivity, along with computed tomography scans before and after failure. The predictions from the damage constitutive equation were compared with experimental results. This comparison shows that the proposed damage variable equation effectively characterizes the damage evolution of sandstone during loading and unloading, and that the constitutive equation closely fits the experimental data. This study provides a theoretical basis for monitoring and assessing the responses of surrounding rock mass during underground excavation.

As a typical solid waste from the iron and steel, the mechanical properties of steel slag are regarded as the core basis for realizing its resource recycling. To explore the influence of shape and external loading speed on the crushing characteristics of steel slag, single particle crushing tests were carried out. The research focuses on the correlation between parameters such as the load–displacement relationship of single particles, crushing mode, crushing energy, and Weibull modulus, as well as external loading rate and quantified morphological parameters. The results show that the single particle crushing modes of steel slag mainly consist of three modes: through-splitting, complete fragmentation and local cutting; Compared with natural aggregates or recycled materials, steel slag particles are found to potentially exhibit higher compressive strength and the increase in loading rate further accelerates the occurrence of particle crushing behavior; Significant impacts on the crushing mode and characteristic stress of steel slag particles are exerted by their shape differences, and the energy release mode is jointly regulated by shape and loading rate. This research provides theoretical guidance and technical support for the diversified utilization of steel slag single particles, a new type of solid waste resource.

The nanofluid-based direct absorption solar collector (NDASC) ensures that solar radiation passing through the tube wall is directly absorbed by the nanofluid, reducing thermal resistance in the energy transfer process. However, further exploration is required to suppress the outward thermal losses from the nanofluid at high temperatures. Herein, this paper proposes a novel NDASC in which the outer surface of the collector tube is covered with functional coatings and a three-dimensional computational fluid dynamics model is established to study the energy flow distributions on the collector within the temperature range of 400–600 K. When the nanofluid’s absorption coefficient reaches 80 m⁻¹, the NDASC shows the optimal thermal performance, and the NDASC with local Sn-In₂O₃ coating achieves a 7.8% improvement in thermal efficiency at 400 K compared to the original NDASC. Furthermore, hybrid coatings with SnIn₂O₃/WTi-Al₂O₃ are explored, and the optimal coverage angles are determined. The NDASC with such coatings shows a 10.22%–17.9% increase in thermal efficiency compared to the original NDASC and a 7.6%–19.5% increase compared to the traditional surface-type solar collectors, demonstrating the effectiveness of the proposed energy flow control strategy for DASCs.

To enhance the resistance of honeycomb sandwich panel against local impact, this study delved into the matching relationship between face sheets and core. An integrated approach, combining experiment, simulation, and theoretical methods, was used. Local loading experiments were conducted to validate the accuracy of the finite element model. Furthermore, a control equation was formulated to correlate structural parameters with response modes, and a matching coefficient λ (representing the ratio of core thickness to face sheet thickness) was introduced to establish a link between these parameters and impact characteristics. A demand-driven reverse design methodology for structural parameters was developed, with numerical simulations employed to assess its effectiveness. The results indicate that the proposed theory can accurately predict response modes and key indicators. An increase in the λ bolsters the structural indentation resistance while concurrently heightens the likelihood of penetration. Conversely, a decrease in the λ improves the resistance to penetration, albeit potentially leading to significant deformations in the rear face sheet. Numerical simulations demonstrate that the reverse design methodology significantly enhances the structural penetration resistance. Comparative analyses indicate that appropriate matching reduces indentation depth by 27.4% and indentation radius by 41.8% of the proposed structure.

Irregularities in the track and uneven forces acting on the train can cause shifts in the position of the superconducting magnetic levitation train relative to the track during operation. These shifts lead to asymmetries in the flow field structure on both sides of the narrow suspension gap, resulting in instability and deterioration of the train’s aerodynamic characteristics, significantly impacting its operational safety. In this study, we firstly validate the aerodynamic characteristics of the superconducting magnetic levitation system by developing a numerical simulation method based on wind tunnel test results. We then investigate the influence of lateral translation parameters on the train’s aerodynamic performance under conditions both with and without crosswinds. We aim to clarify the evolution mechanism of the flow field characteristics under the coupling effect between the train and the U-shaped track and to identify the most unfavorable operational parameters contributing to the deterioration of the train’s aerodynamic properties. The findings show that, without crosswinds, a lateral translation of 30 mm causes a synchronous resonance phenomenon at the side and bottom gaps of the train-track coupling, leading to the worst aerodynamic performance. Under crosswind conditions, a lateral translation of 40 mm maximizes peak pressure fluctuations and average turbulent kinetic energy around the train, resulting in the poorest aerodynamic performance. This research provides theoretical support for enhancing the operational stability of superconducting magnetic levitation trains.

Ventilation systems are critical for improving the cabin environment in high-speed trains, and their interest has increased significantly. However, whether air supply non-verticality deteriorates the cabin air environment, and the flow mechanism behind it and the degree of deterioration are not known. This study first analyzes the interaction between deflection angle and cabin flow field characteristics and ventilation performance. The results revealed that the interior temperature and pollutant concentration decreased slightly with increasing deflection angle, but resulted in significant deterioration of thermal comfort and air quality. This is evidenced by an increase in both draught rate and non-uniformity coefficient, an increase in the number of measurement points that do not satisfy the micro-wind speed and temperature difference requirements by about 5% and 15%, respectively, and an increase in longitudinal penetration of pollutants by a factor of about 5 and the appearance of locking regions at the ends of cabin. The results also show that changing the deflection pattern only affects the region of deterioration and does not essentially improve this deterioration. This study can provide reference and help for the ventilation design of high-speed trains.