Search Results (1,232)

Seismic action significantly affects the mechanical properties and failure characteristics of bridge pile foundations, soft rocks, and sediments. This study, by integrating shaking table tests, numerical simulations, and on-site monitoring, systematically analyzed the influence mechanisms of seismic intensity, sediment characteristics, and pile foundation layout on structural responses. Tests show that the 2.5-layer rock–sand pile exhibits nonlinear bearing degradation under seismic force: when the seismic acceleration increases from 0 to 100 m/s², the bearing capacity of the pile foundation decreases by 55.3%, and the settlement increases from 3.2 mm to 18.5 mm. When the acceleration is ≥2 m/s², the cohesion of the sand layer is destroyed, causing a semi-liquefied state. When it is ≥10 m/s², the resistance loss reaches 80%. The increase in pore water pressure leads to dynamic settlement. When the seismic acceleration is greater than 50 m/s², the shear modulus of the sand layer drops below 15% of its original value. The thickness of the sediment has a nearly linear relationship with the reduction rate of the bearing capacity. When the thickness increases from 0 to 1.4 cm, the reduction rate rises from 0% to 55.3%. When the thickness exceeds 0.8 cm, it enters the “danger zone”, and the bearing capacity decreases nonlinearly with the increase in thickness. The particle size is positively correlated with the reduction rate. The liquefaction risk of fine particles (<0.1 mm) is significantly higher than that of coarse particles (>0.2 mm). The load analysis of the pile cap shows that when the sediment depth is 140 cm, the final bearing capacity is 156,187.2 kN (reduction coefficient 0.898), and the maximum settlement is concentrated at the top point of the pile cap. Under the longitudinal seismic load of the pile group, the settlement growth rate of the piles containing sediment reached 67.16%, triggering the dual effect of “sediment–earthquake”. The lateral load leads to a combined effect of “torsional inclination”, and the stress at the top of the non-sediment pile reaches 6.41MPa. The seismic intensity (PGA) is positively correlated with the safety factor (FS) (FS increases from 1.209 to 37.654 when 10 m/s²→100 m/s²), while sediment thickness (h) is negatively correlated with FS (FS decreases from 2.510 to 1.209 when 0.05 m→0.20 m). The research results reveal the coupled control mechanism of sediment characteristics, seismic parameters, and pile foundation layout on seismic performance, providing key parameters and an optimization basis for bridge design in high-intensity areas. Full article

Bone tissue engineering, as an important branch of regenerative medicine, integrates multidisciplinary knowledge from cell biology, materials science, and biomechanics, aiming to develop novel biomaterials and technologies for functional repair and regeneration of bone tissue. Hydrogels are among the most commonly used scaffold materials; however, conventional hydrogels exhibit significant limitations in physical properties such as strength, tensile strength, toughness, and fatigue resistance, which severely restrict their application in load-bearing bone defect repair. As a result, the development of high-strength hydrogels has become a research hotspot in the field of bone tissue engineering. This paper systematically reviews the latest research progress in this area: First, it delves into the physicochemical characteristics of high-strength hydrogels at the molecular level, focusing on core features such as their crosslinking network structure, dynamic bonding mechanisms, and energy dissipation principles. Next, it categorically summarizes novel high-strength hydrogel systems and different types of biomimetic hydrogels developed based on various reinforcement strategies. Furthermore, it provides a detailed evaluation of the application effects of these advanced materials in specific anatomical sites, including cranial reconstruction, femoral repair, alveolar bone regeneration, and articular cartilage repair. This review aims to provide systematic theoretical guidance and technical references for the basic research and clinical translation of high-strength hydrogels in bone tissue engineering, promoting the effective translation of this field from laboratory research to clinical application. Full article

The traction behavior of lubricant films forms the foundation of dynamic modeling for aeroengine mainshaft ball bearings. Its accuracy directly determines the reliability of predicted dynamic responses and the available design safety margins. Existing traction models produce artificial friction in the zero slip region and exhibit strong sensitivity to ball size effects, which leads to significant deviations from experimental observations. These limitations make them unsuitable for high-fidelity analyses of aeroengine mainshaft bearings. In this study, a self-developed high-speed traction test rig was used to systematically measure the traction–slip responses of three aviation lubricants, including the newly developed 4102 (7 cSt) and the inservice 4050 (5 cSt) and 4010 (3 cSt). The tests covered a wide range of operating conditions, including maximum Hertzian pressures of 1.0 to 1.5 GPa, oil supply temperatures of 25 to 120 °C, entrainment speeds of 25 to 40 m/s, and slide–roll ratios (SRR) of 0 to 0.3. The evolution of lubricant traction characteristics was examined in detail. Based on the experimental data, a four-parameter and three-coefficient traction model was proposed. This model eliminates the non-physical traction outputs at zero slip observed in previous formulations. When embedded into the bearing dynamic simulations, the maximum deviation between the predicted friction torque and the measured values is only 3.79%. On the basis of typical operating conditions of aeroengine bearings, lubricant selection guidelines were established. Under combined high-speed, light-load, and high-temperature conditions, the high-viscosity lubricant 4102 is preferred because it suppresses cage sliding and enhances film stiffness. When the cage slip ratio is below 15% and lubrication is sufficient, the low-viscosity lubricant 4010 is recommended, followed by 4050, in order to reduce frictional heating. This study provides a theoretical basis for high-accuracy dynamic design and lubricant selection for aeroengine ball bearings. Full article

The success of invasive species relies heavily on the production, dispersal and genetic composition of propagules. For range expanding species, breeding strategy and level of reproductive investment will strongly influence their capacity to establish and invade new areas. A hermaphroditic lifestyle provides the advantage of increasing the number of seed bearing individuals within a population while a dioecious habit may enable more rapid adaptation to new environments, improve resource use efficiency, fecundity and dispersal. Pittosporum undulatum, a tree native to coastal areas of southeastern Australia, has many characteristics of an invasive species within and beyond its native range. A previous study detected a male bias within invasive populations, with a high proportion of fruit deriving from female-only trees, leading to recommendations for the removal of ‘matriarch’ trees as a simple management technique. We expanded that study and investigated breeding systems of different populations of P. undulatum by assessing tree density, gender, resource availability and fruit load of 871 individuals in seven native and seven invasive populations. All populations comprised either females (47%) or hermaphrodites. No male-only trees were observed within the study. More females produced more fruit than hermaphrodites, especially in the native site. This could not be attributed to environmental differences between sites. These data support the current management practices of targeting the removal of females as a simple method for containing invasions given the benefits of reducing the workload and spreading limited management resource. Our work highlights the value in understanding the breeding strategy employed by focal invasive species as a means of developing improved and more targeted control methods. Full article

Current studies on large-span structural components have largely emphasized flexural performance, whereas multi-ribbed profiled steel sheeting-concrete composite slabs may be prone to inclined-section shear failure in the construction stage, particularly at small shear-span ratios. To ensure that the vertical shear capacity of such composite slabs satisfies construction-stage requirements, a numerical model validated against experimental evidence was employed. A systematic parametric study was conducted to clarify the influence of key structural parameters and the shear-span ratio on the vertical shear resistance. On this basis, a calculation method for the vertical shear capacity was proposed based on the strength-equivalence principle and verified against numerical results. The results indicate that the inclined-section shear failure of multi-ribbed profiled steel sheeting-concrete composite slabs develops through four characteristic stages, the shear-span ratio governs the transition of failure mode, and slabs with a rib height of h = 150 mm exhibit a pronounced shear-dominated failure when the shear-span ratio is less than 2. Increasing the rib inclination angle degrades the composite interaction between the profiled steel sheeting and concrete, whereas increasing the sheeting thickness and slab depth enhances the load-bearing capacity and stiffness, and longitudinal reinforcement benefits the internal stress redistribution of concrete. A vertical shear capacity model was formulated for the novel multi-ribbed profiled steel-concrete composite slab and verified against numerical results. The research helps to bridge the gap in studies on the vertical shear performance of multi-ribbed profiled steel-concrete composite slabs and offers design guidance for vertical shear checks of composite slabs in the temporary construction stage. Full article

To address the conflicting demands of lightweight materials and high load-bearing capacity in high-end fields such as aerospace and biomedical engineering, there is an urgent need to conduct research on the mechanical behavior and response mechanism of porous titanium alloy structures. In this paper, a combination of experimental testing, numerical simulation, and theoretical analysis was employed to conduct the research. A titanium alloy porous structure with different porosities was constructed based on classical three-period minimal surface optimization, and its preparation was completed using advanced selective laser melting technology. A multidimensional characterization experimental device was established to accurately obtain its mechanical performance data. It was found that the mechanical behavior of the structures is insensitive to loading rates, but more sensitive to their structural volume fraction. The quantitative characterization of microstructure damage and fracture morphology, as well as the identification of failure modes, indicates that the microstructure damage of the porous metal exhibits a ductile–brittle synergistic damage characteristic. By combining high-precision numerical simulation technology, the damage modes and damage evolution laws of porous metal structures in titanium alloys were comprehensively elucidated. By analyzing energy dissipation and constructing evaluation indicators for energy absorption efficiency, the energy absorption characteristics of the porous metal structure were elucidated, and the interaction behavior and correlation mode between the platform stress and the structural volume fraction of the porous metal structure were accurately described. Full article

Traditional physical similarity simulation methods struggle to replicate the cumulative unloading–expansion effect in overburden, particularly due to inherent limitations in representing the bulking–compaction behavior of fractured rock masses in the caving zone. This significantly hinders a deeper understanding of overburden movement mechanisms. To address this technical challenge, this study innovatively proposes an experimental method designed to simulate the bulking–compaction process of rock masses in the caving zone. The method employs a composite of EPE and PP sheets. Through systematic uniaxial compression tests and orthogonal experimental design optimization, an optimal material mix ratio with superior performance was identified. Its stress–strain behavior was systematically analyzed, and its feasibility was comprehensively verified from the perspective of the synergistic evolution of displacement and stress fields. The results demonstrate that the stress–strain response of the new similar simulation material (SSM) aligns highly with the Salamon model. Furthermore, its load-bearing capacity exhibits a non-linear strengthening characteristic with increasing EPE thickness. Physical simulation validation tests, based on the engineering context of the Shilawusu Coal Mine, showed that all the relative error parameters were strictly controlled within 12%. The overall accuracy was significantly superior to existing simulation methods, achieving a substantial reduction in prediction errors for key parameters. Full article

During mining, rock failure and water infiltration induce variations in deformation, energy release, electrical conductivity, and water content. Their response laws underpin water-preserving mining optimization, environmental impact mitigation, and mining area sustainability, while facilitating the prediction of stratum instability and water migration. In this study, uniaxial compression experiments were conducted on sandstone with different water saturations, during which the responses of strain, acoustic emission energy, and electrical resistivity were monitored. The temporal characteristics of the rock’s multi-parameter responses were analyzed, and the influence of water content on precursor information of rock failure was revealed. Multi-parameter response equations for rocks under loading, incorporating the effect of water saturation, were established. A segmented variable-weight-integrated damage constitutive model for water-bearing rocks was developed based on the multi-parameter responses. The findings showed that the temporal characteristics of multi-parameter coupling responses can reflect the damage evolution and pore water migration during the instability and failure process of water-bearing rocks. As water saturation increased from 0% to 100%, the rock exhibited the following variations: peak stress decreased by 38.49%, strain at peak stress increased by 8.79%, elastic modulus decreased by 41.58%, cumulative acoustic emission energy drops by 93.23%, and initial electrical resistivity plummets by 98.02%. Compared with the theoretical stress–strain curves based on strain damage variables, cumulative acoustic emission energy damage variables, and electrical resistivity damage variables, the theoretical stress–strain curve based on the integrated damage variable shows better agreement with the measured curve, with the coefficient of determination exceeding 0.98. The research findings offer valuable insights into rock mass instability and groundwater migration, supporting water-preserving mining and sustainable mining area development. Full article

The use of polyamide-12 (PA12) thermoplastics in additive manufacturing (AM) is promising owing to their mechanical properties and printability. However, in load-bearing applications, improvements in mechanical strength and stiffness are sought after. Herein, the reinforcement efficiency of silicon nitride (Si₃N₄) nanoparticles in the PA12 matrix was explored. The filler loading varied between 2.0 wt. % and 10.0 wt. %. The nanocomposites were extruded into filament using melt compounding for subsequent material extrusion (MEX) 3D printing. PA12/Si₃N₄ nanocomposites were examined for their thermal, rheological, morphological, and structural characteristics. For mechanical characterization, flexural, tensile, microhardness, and Charpy impact data were obtained. For structural examination, porosity and dimensional deviation were assessed. Scanning electron microscopy (SEM) was used to investigate morphology and chemical composition. The results indicate that Si₃N₄ nanopowder significantly improved all mechanical properties, with a greater than 20% increase in tensile strength and elastic modulus when compared to neat PA12. The structural characteristics were also improved. These findings indicate that Si₃N₄ nanoparticles provide a viable reinforcement filler for PA12 for use in lightweight, robust structural components fabricated using MEX AM. Furthermore, it can be stated that ceramic–polymer nanocomposites further improve the applicability of PA12, where high mechanical performance is required. Full article

Aerostatic bearings incorporating micro-hole restrictors with diameters on the order of tens of microns demonstrate superior static and dynamic stiffness characteristics, while significantly reducing air consumption, and are increasingly adopted in precision engineering applications. This paper investigates the modelling of aerostatic bearings with micro-hole restrictors. First, a refined discharge coefficient formula is developed, incorporating the orifice length-to-diameter ratio effect using the computational fluid dynamics (CFD) simulation results on a centrally fed circular aerostatic bearing. A numerical solution scheme is proposed using the developed discharge coefficients to enable more accurate and efficient prediction of the bearing performance and flow characteristics. Finally, the proposed numerical approach is implemented using the finite difference method (FDM) and demonstrated through a circular thrust air bearing case study. The results are validated against both CFD simulations and experimental measurements, showing excellent agreement and confirming the reliability of the FDM-based numerical model. Numerical and experimental investigations consistently demonstrate that micro-hole-restricted air bearings can achieve both high load capacity and high stiffness, having the potential for application in more complex air bearing designs and systems. Full article

Addressing technical challenges in personalized fabrication and mechanical regulation of bioresorbable vascular scaffolds, this study pioneers an electric field-driven melt jetting rotational printing technique to fabricate polycaprolactone (PCL) scaffolds (Ø3–8 mm). Multiscale characterization confirms a rhombic mesh macrostructure with uniform fibers and fusion-enhanced nodal junctions, demonstrating synergistic control of electrohydrodynamic forces and surface tension over microfiber deposition. Mechanical testing reveals triphasic tensile behavior (elastic-plastic-fracture), where 5 mm scaffolds exhibit 38% enhanced peak load due to superior interfacial bonding and densified geometry, while 8 mm counterparts suffer premature failure from structural weakening. Fractography identifies brittle fracture initiation at stress-concentrated nodes versus ductile dominance in straight segments, confirming co-regulation by intrinsic material properties and architecture. Compression tests demonstrate characteristic load-holding-recovery behavior, with 20% increased load-bearing capacity and enhanced elastic recovery in larger scaffolds. This work establishes a structure–property correlation framework for optimizing degradable vascular implants, providing novel methodologies and theoretical foundations for clinical compatibility. Full article

Pre-tensioned T-beams with polygonal tendons offer high load-bearing capacity and suitability for large spans, demonstrating broad application potential in bridge engineering. The cracking state of a prestressed beam is a crucial indicator for assessing its service state, while the ultimate bearing capacity is a key metric for structural safety. In this study, we designed a novel 30 m pre-tensioned T-beam with polygonal tendons and investigated its shear cracking performance and ultimate bearing capacity under a shear-span ratio of 2.5 through a full-scale test. A graded loading protocol was employed. The results indicate that during the initial loading stage, the shear cracking load of the inclined section was 1766 kN. A distinct inflection point appeared on the load–displacement curve, accompanied by a significant reduction in stiffness. Cracks initially developed at the junctions between the web and the top flange, as well as the diaphragm, and subsequently propagated towards the shear–flexural region, exhibiting typical shear–compression failure characteristics. During the secondary loading to the ultimate state, the beam demonstrated good ductility and stress redistribution capability. The ultimate shear capacity reached 3868 kN. Failure occurred by crushing of the concrete in the compression zone after the critical inclined crack penetrated the web, with the member ultimately reaching its ultimate capacity through a plastic hinge mechanism. Strain analysis revealed that the polygonal tendons effectively restrained the premature development of inclined cracks, thereby enhancing the overall shear performance and deformation capacity. This study verifies the mechanical performance of the new T-beam under a shear span-to-depth ratio of 2.5 through calculations based on different codes and finite element numerical analysis, providing experimental evidence and theoretical references for its engineering application. Full article

Background/Objectives: Bone defects remain widespread. Type I collagen–hydroxyapatite composites suit bone engineering by mimicking matrix structure, making them pertinent materials for bone tissue engineering across a range of defect types. Their application is well aligned with non-load-bearing conditions, while use in load-bearing sites requires mechanical properties that meet the demands of those environments. Marine collagen offers a low-cost source from processing by-products. This work aimed to develop perch collagen–hydroxyapatite scaffolds for bone tissue engineering. Methods: Composites with COLL:HAp ratios of 100:0, 50:50, 40:60, and 30:70 were prepared. After crosslinking and freeze-drying, porosity and water absorption were examined. SEM and X-EDS assessed morphology and elemental distribution. FT-IR confirmed the chemical composition. Compression tests evaluated mechanical behavior. Cell viability and colonization assessed the biological performance. Biodegradability, thermal stability, and antimicrobial activity were also determined. Results: FT-IR confirmed the characteristic absorption bands of both components. SEM and swelling behavior showed porous, interconnected structures with uniform hydroxyapatite dispersion. X-EDS indicated Ca/P ratios consistent with hydroxyapatite. Thermal analysis demonstrated scaffold stability. Compression tests showed mechanical resistance for all the scaffolds, with stiffness increasing with the inorganic content. Perch collagen enhanced biological functionality, supporting osteoblast viability and colonization. Biodegradation gradually proceeded. Antibacterial activity against the tested pathogens was detectable, though moderate. Conclusions: The developed scaffolds combined structural stability, controlled degradation, and favorable cell response, constituting a viable and promising candidate for applications in bone tissue engineering. Full article

To study the creep compression characteristics and evolution mechanism of pressure-bearing graded crushed rock under constant load. Creep compression tests of crushed rock were conducted using the self-developed confined compression test system under different Talbot indexes and axial stresses. The axial displacement, void ratio, mass distribution, fractal dimension, and fragmentation of crushed rock during creep compression were analyzed. And the void ratio-fractal dimension model of crushed rock under pressure was established. The results reveal three-stage characteristics in axial displacement and void change, which correspond to rapid, attenuation, and stable change processes. The axial displacement and fragmentation amount are positively correlated with the axial stress and Talbot index, while the porosity is negatively correlated with them. The fractal dimension shows a positive correlation with axial stress and a negative correlation with the Talbot index. Additionally, a theoretical model was established to characterize the dynamic correlation between void ratio and fractal dimension during compression process, and its accuracy was verified, with a maximum error of only 0.0819. The research findings can provide insights for stability prediction and deformation control of crushed rock in engineering applications such as building foundation pits, ground treatment, and coal mine goafs. Full article

The mechanical performance of rail fasteners plays a crucial role in the track–structure interaction of high-speed railways. A reasonable lateral stiffness of the fastener system can enhance the stability and safety of train operation and prevent derailment accidents. Under seismic action, adjacent bridge spans undergo reciprocating displacement, causing the rail-fastener system near the beam ends to be subjected to lateral cyclic forces. To investigate the mechanical and deformation behavior of the WJ-8B fastener system under lateral loading, low-cycle reciprocating loading tests were conducted on the rail-fastener system considering different bolt torques. The load–displacement curves and torque–rotation curves of the fastener system were obtained, and formulas for calculating the characteristic values of the mechanical properties of the WJ-8B fastener system were fitted, which show good agreement with the experimental results. The results indicate that the lateral mechanical behavior of the WJ-8B fastener exhibits significant nonlinear characteristics, marked by three distinct inflection points in the load–displacement curve that delineate five stages: initial stage, rail shearing stage, rail sliding stage, rail contact stage, and three-point contact. The bolt torque is positively correlated with the lateral stiffness of the fastener system. Increasing the torque from 115 N·m to 190 N·m enhances the lateral bearing capacity by 29.06% in the push direction and by 38.74% in the pull direction. Meanwhile, the system torque decreases by 21.45% in the push direction and increases by 21.14% in the pull direction. Full article