Search Results (7,138)

This study focuses on the mechanical behavior of iron ore failings as base materials for roads. It is the first to systematically integrate freeze–thaw static load tests, SHPB dynamic tests, PFC discrete element microscopic simulation, and road stability analysis, to reveal the coupling mechanism of freeze–thaw, confining pressure and loading rate in cold environments, and to clarify the critical threshold of porosity and the safe threshold of failing content, as well as the intrinsic relationship between force chain evolution and macroscopic strength degradation. Firstly, a two-dimensional particle flow model of iron ore failing aggregates (150 mm × 150 mm, 11,530 particles) was constructed using PFC2D 2025 software, and the optimal microscopic parameters such as normal stiffness of 350 N/m and tangential stiffness of 175 N/m were determined (the error between simulation and experimental peak strength is less than 2.5%). The study revealed a negative correlation between high loading rate, local dense force chain and overall strength reduction. The initial porosity critical threshold is 0.23, and the optimal control range is 0.18–0.23 (this threshold varies with particle gradation). Secondly, taking iron ore failings from Lanzhou Daiquiri County, Sichuan Province, as the object, the static mechanical degradation law under freeze–thaw cycles (porosity from 7.5% to 9.5%, elastic modulus decreased by 52.3%, peak strength decayed by 13.0%) was clarified. The three-dimensional coupling effect of freeze–thaw times, confining pressure, and loading rate was investigated. The loading rate was also revealed (the average strength increased by 15% due to confining pressure, and the dynamic strength dropped to 110.2 MPa after 50 freeze–thaw cycles). Finally, the stability of the iron failing roadbed was analyzed, and it was found that the tailing content and safety factor FS(x) decreased linearly, the correction coefficient k(x) increased linearly, and the critical content was 66.67% (FS = 1.3), reaching the specification threshold. The poor tailing gradation led to insufficient stability, and stabilization agents were needed for improvement. This study did not investigate the long-term freeze–thaw durability, dissolution risks, and optimal dosage of the stabilizer, and thus has certain limitations. Full article

Amid the global transition to low-carbon energy systems, unconventional oil and gas resources play a key role in ensuring energy security. Hydraulic fracturing is a central technology for unconventional resource development, but it may also induce seismicity. This study investigates energy release and induced seismicity during hydraulic fracturing in naturally fractured media. A fully coupled hydro-mechanical-damage (HMD) model combined with a discrete fracture network (DFN) is developed to represent natural fractures in shale reservoirs. By incorporating frictional contact and shear slip, the model simulates tensile propagation of hydraulic fractures and shear slip of natural fractures. Parameter sensitivity analyses are conducted for natural fracture characteristics, differential stress, elastic modulus, and injection rate. The energy release of shear slip and tensile propagation is compared based on total seismic moment. Results show that the seismic moment generated by natural fracture shear slip is several orders of magnitude higher than that from tensile propagation, indicating that shear slip is the dominant energy release mechanism. Increasing the number and length of natural fractures enhances fracture-network connectivity and pressure diffusion, making natural fractures more prone to shear instability. Higher differential stress, elastic modulus, and injection rate may further promote slip-induced energy release and elevate induced seismic risk. These findings provide a theoretical basis for seismic risk assessment and parameter optimization in hydraulic fracturing. Full article

The geometric characteristics of these fractures have a substantial influence on the mechanical and energy properties of heterogeneous rocks. This study calibrated the experimental results using the finite-discrete element method (FDEM). An orthogonal design was employed to investigate the effects of the homogeneity coefficient, fracture angle, fracture length, and fracture aperture on the mechanical and energy characteristics of fractured sandstone. The main factors influencing the mechanical properties and energy characteristics of rocks were explored through multi-factor correlation analysis. The effects of fracture geometric features and heterogeneity on the mechanical properties and energy characteristics of rocks were analyzed by single-factor analysis. A regression model between peak stress and fracture geometric features was established. The results show the following: The homogeneity coefficient and fracture length have a significant impact on the elastic modulus of fractured sandstone. The fracture angle and fracture length have a significant influence on the peak strain, elastic strain energy and total energy of fractured sandstone. The fracture angle, fracture length and homogeneity coefficient have a significant effect on the peak stress of fractured sandstone. The elastic modulus and peak stress show a logarithmic relationship with the homogeneity coefficient, while the elastic strain energy and total energy have a logarithmic relationship with the crack length. The peak strain and peak stress have a quadratic polynomial relationship with the crack angle, and the elastic strain energy and total energy also have a quadratic polynomial relationship with the crack angle. The elastic modulus, peak strain, and peak stress have a logarithmic relationship with the crack length. The predicted values of peak stress and numerical calculation errors of fractured rocks mainly range from 0.07% to 7.76%, with an average error of 2.58%. Both the peak stress prediction values and the numerical calculation results show a “U”-shaped change trend, first decreasing and then increasing with the increase in the fracture angle. This study investigates the influence of fracture geometric characteristics on the mechanical and energy characteristics of heterogeneous rocks, which is of great significance for the stability control of fractured rock masses and the optimization of underground engineering parameters. The core challenge for future research lies in revealing the intrinsic connection among fracture geometric features, rock mass heterogeneity, and multi-field coupling effects to meet the complex engineering demands of deep mining, thereby serving the safe production and disaster prevention of deep mines. Full article

In cold-region open-pit mine slopes, damage accumulation and mechanical deterioration induced by in situ stress and seasonal freeze–thaw alternation can easily trigger sudden instability. To investigate the effects of temperature difference under coupled constant loading and freeze–thaw action on the mechanical response and failure precursors of rock, based on the self-developed TCDR-I temperature–stress coupled testing system, uniaxial compression tests and real-time acoustic emission monitoring were conducted on water-saturated sandstone under a constant load of 1.4 MPa and multiple freeze–thaw temperature gradients. The mechanical behavior of freeze–thawed water-saturated sandstone and the acoustic emission characteristics during failure were analyzed. Combined with critical slowing down theory, the failure precursor characteristics of water-saturated sandstone under freeze–thaw action were investigated, and the internal mechanism of damage accumulation and defect evolution under the coupled effects of constant load and freeze–thaw temperature difference was revealed. The results show that, with increasing freeze–thaw temperature difference, the number of cracks and crack ratio in the loaded water-saturated sandstone gradually increased, whereas the compressive strength, elastic modulus, and total strain energy gradually decreased. After freeze–thaw treatment at −40 to 20 °C, the compressive strength, elastic modulus, and total strain energy decreased by 19.24%, 13.72%, and 44.77%, respectively, compared with those of the unfrozen–thawed specimens. During specimen failure, the dominant crack type gradually shifted from shear cracking to tensile cracking. The acoustic emission b-value and precursor points identified from multiparameter variance can both be used as criteria for predicting specimen failure. The warning lead time increased with increasing freeze–thaw temperature difference. After freeze–thaw treatment at −40 to 20 °C, the predicted failure times based on these two indicators preceded the actual failure time by 11.05 s and 16.19 s, respectively. The findings provide a theoretical basis for the early warning of sudden disasters in rock masses in cold-region engineering. Full article

Traffic congestion and air pollution caused by rapid urbanization have emerged as critical challenges in metropolitan areas worldwide. Urban air mobility (UAM), particularly electric propulsion-based systems, has gained attention as a promising solution. For the successful commercialization of UAM, a lightweight airframe design with ensured structural integrity is essential. This study proposes an optimized lightweight design process that integrates automated composite manufacturing with artificial intelligence (AI)-based material property prediction. Finite-element analysis (FEA) was performed on glass fiber-, basalt fiber-, and carbon fiber-reinforced polymers under identical deformation conditions to derive design material properties in terms of elastic modulus and weight reduction. A large-scale dataset of fiber-reinforced plastics was established through an automated manufacturing process, and a deep learning regression model was developed using Altair AI Studio to predict mechanical properties under untested material and process conditions. The predicted properties were applied to a UAM fuselage model, and FEA results demonstrated that composite structures achieved equivalent or superior stiffness with up to 50% weight reduction compared to aluminum. In addition, inverse reserve factor (IRF) analysis confirmed structural safety, with all configurations maintaining IRF values below 1. The proposed AI-driven framework provides a scalable and data-driven lightweight design methodology applicable to next-generation UAM and advanced air mobility structures. Full article

Negative Poisson’s ratio (NPR) bars, as novel materials, exhibit a significant volumetric dilation effect under tension. Compared to conventional reinforcement, NPR bars offer distinct advantages, including high ductility, high strength, and superior corrosion resistance. This study investigates the tensile properties of three types of NPR bars: the bare round bar, spiral ribbed bar, and steel strand. Their bond behavior with concrete was examined through central pull-out tests, considering the influences of bar type, NPR bar diameter, and anchorage length. The analysis focuses on the tensile mechanical properties, characteristics of the bond–slip curves, failure modes, and the development of predictive models for key bond–slip parameters. The results indicate that all three NPR types possess a high elastic modulus and exceptional ductility. The bare round bar achieved an elongation at break of 51.2%, with only minor necking observed at the fracture surface. The bond failure mode is influenced by bar type, NPR bar diameter, and anchorage length: pull-out failure occurred for the bare round bar, spiral ribbed bar with short anchorage length, and small-diameter steel strand, whereas splitting failure was observed for the spiral ribbed bar with long anchorage length. The large-diameter strand exhibited a combined splitting–pull-out failure. Furthermore, the bond–slip curves for the bare round bar and steel strand displayed two distinct peak strengths. The bond strength of the bare round bar increased with longer anchorage length, while it decreased for both the spiral ribbed bar and steel strand. Empirical models developed based on experimental data demonstrate good predictive accuracy for the bond performance of the different bar types. Full article

Additive manufacturing using vat photopolymerization (VPP) resin materials has gained attention for fabricating dental prostheses; however, the effects of material type and build angle on their properties remain unclear. We compared the mechanical properties of two filler-containing VPP hybrid resins, SprintRay Ceramic Crown (CC) and OnX Tough 2 (OT), with those of a conventional polymethyl methacrylate (PMMA) disc material, and evaluated the influence of build angle on surface characteristics, dimensional accuracy, and mechanical performance. Specimens were fabricated using a DLP system at build angles of 0°, 45°, and 90°. Vickers hardness, surface morphology and roughness, dimensional deviations, flexural strength, elastic modulus, and fracture energy were assessed according to relevant standards. CC exhibited significantly higher hardness and elastic modulus than PMMA and OT, whereas OT showed the highest fracture energy. Surface morphology and roughness were strongly affected by build angle, with 45° producing distinct periodic patterns and increased roughness. Dimensional evaluation revealed a tendency toward overbuilding, particularly in the vertical direction at 45°. Flexural properties were also influenced by build angle, with 45° generally providing favorable performance. Both material composition and build angle affect VPP-fabricated dental resin performance, highlighting the importance of appropriate material and processing selection for clinical applications. Full article

Optimizing sports bra performance is important for improving exercise safety and wearer well-being. This study systematically quantifies the biomechanical interaction between strap elastic modulus (834.6–3087.2 N/m) and vertical breast motion control in plus-size cohorts (C–F cups). Fifteen healthy participants performed treadmill running at 7.5 km/h, while breast kinematics were captured via 3D motion capture integrated with subjective comfort assessments. Results demonstrate a nonlinear mechanical trend between strap modulus and vertical breast displacement. Specifically, both logarithmic (B = 91.923 − 8.257 ln(E)) and power function (B = 221.44 E^−0.268) models illustrate the observed nonlinear trend, characterizing the diminishing marginal utility of increased material stiffness. While elevating modulus significantly attenuates oscillation amplitude, the inhibitory effect plateaus at higher levels due to breast tissue viscoelasticity. Qualitative feedback indicates that excessive rigidity elevates perceived shoulder pressure, thereby compromising ergonomic comfort. Consequently, this research advocates for a systemic equilibrium between motion attenuation and wearer tolerance, proposing an optimal strap modulus bandwidth of 2000–2500 N/m for the evaluated 85D prototype. Full article

Glass fiber–reinforced polymer (GFRP) reinforcement provides an effective alternative to conventional steel in concrete structures due to its corrosion resistance. Nevertheless, the lower elastic modulus of GFRP necessitates careful consideration of serviceability behavior in GFRP-reinforced concrete members. This study presents a numerical sectional analysis model for predicting the flexural response and ultimate capacity of hybrid reinforced concrete beams incorporating embedded GFRP profiles in combination with either mild steel or GFRP reinforcement bars under monotonic static loading. The proposed model employs realistic nonlinear stress–strain relationships for concrete and steel, together with secant moduli of elasticity evaluated at different loading stages. Particular emphasis is placed on detailed stress distribution in flexural sections, including the contribution of tension stiffening in the post-cracking regime. The formulation integrates nonlinear constitutive material behavior with theoretical sectional equilibrium to evaluate the effective flexural secant stiffness. For practical serviceability assessment and to reduce dependence on complex analytical procedures, strain vectors and stiffness matrix components are derived using elasticity coefficients that reflect modulus degradation obtained from numerical analysis. The accuracy of the model is verified through comparison with experimental results, including ultimate flexural capacity and moment–deflection responses. Many crucial parameters were studied, such as the longitudinal reinforcement ratio, type of reinforcement, concrete compressive strength, position of the I-GFRP profile, and rotation of the I-GFRP profile. The results of this study demonstrated that both the longitudinal reinforcement ratio and the rotation of the I-GFRP profile have a significant influence on the ultimate load capacity and deflection behavior. The close agreement between numerical predictions and experimental observations demonstrates the reliability and applicability of the proposed model for structural engineering analysis and design. Full article

This study investigates the elastic anisotropy and thermodynamic properties of the L1₂-type ScAl₃ phase under extreme conditions (0–1500 K and 0–50 GPa) using first-principles calculations. The elastic constants were determined using a precise stress–strain method, with polycrystalline moduli derived via the Voigt–Reuss–Hill (VRH) approximation. A systematic analysis was conducted to characterize the elastic anisotropy of Young’s modulus, shear modulus, and Poisson’s ratio. Results demonstrate that ScAl₃ is mechanically stable and exhibits near-perfect elastic isotropy (A^U = 0.0001). Thermodynamic analysis via the quasi-harmonic Debye–Grüneisen model reveals that the phase maintains its structural integrity and significant heat resistance up to 1500 K, despite thermal softening. These findings provide theoretical insights into the physical nature of ScAl₃ intermetallics and offer quantitative guidance for the design and thermal treatment of Sc-reinforced aluminum alloys in high-temperature aerospace applications due to their superior combination of strength and toughness. Full article

Polyetheretherketone (PEEK), a high-performance thermoplastic, is utilized in bone tissue engineering due to its elastic modulus resembling that of human cortical bone. However, toxicological studies on PEEK remain limited. PEEK disrupts bone homeostasis by recruiting macrophages and inducing the aggregation of foreign body multinucleated giant cells, ultimately leading to bone resorption. The lack of effective therapeutic approaches underscores the importance of identifying novel treatments. This study systematically investigated the potential molecular mechanisms underlying PEEK-induced bone resorption using network toxicology, molecular docking techniques, and molecular dynamics simulations. We first conducted a network-based toxicological assessment based on the molecular structure of PEEK. By integrating and screening targets from multiple databases, we identified 139 potential targets associated with PEEK-induced bone resorption and constructed an interaction network diagram of these targets. Gene Ontology (GO)/KEGG enrichment analysis revealed that PEEK may induce bone resorption through pathways such as the PI3K-AKT signaling pathway and TNF signaling pathway. Further analysis using STRING and Cytoscape 3.9.0 software identified 53 core targets, including MAPK3, TNF, IL-6, AKT1, IL-1β, EGFR, and MMP9. We found that enriched highly correlated pathways encompassed core targets, supporting the scientific hypothesis that PEEK induces bone resorption. Furthermore, molecular docking and molecular dynamics simulation results confirmed that PEEK exhibits strong binding affinity with core targets, forming stable complexes. In summary, this study not only reveals the potential biological mechanisms underlying PEEK-induced bone resorption but also provides new evidence for future prevention and treatment of PEEK-induced bone imbalance. Full article

Since tires from end-of-life vehicles are not entirely biodegradable and pose a serious environmental problem, their disposal has become a significant global environmental concern. One technique to decrease these environmental issues is incorporating waste rubber to make sustainable green concrete. This study examined the usage of waste supplementary cementitious materials (SCMs) such as fly ash (FA), metakaolin (MK), marble powder (MP), slag (SL), and silica fume (SF) for surface precoating of crumb rubber (CR) to improve the mechanical properties of the produced crumb rubber concrete (CRC) by strengthening the bond between CR and cement paste in the interfacial transition zone (ITZ). The CR replaced (0, 15%, and 25%) of sand by weight in the preparation of CRC mixtures. A total of eleven CRC mixes were cast to investigate the fresh properties, compressive strength, and splitting tensile strength. In addition, the compressive stress-strain curve was investigated, and peak stress, peak strain, energy absorption, toughness, and modulus of elasticity have been evaluated. The outcomes showed that precoating CR using FA, followed by MK, has the strongest effect on increasing CRC compressive performance. The 25% substitution of sand with FA-treated CR increased compressive strength after 28 days, splitting tensile strength, peak stress, toughness, and modulus of elasticity by 34.7%, 23.7%, 34.8%, 26.1%, and 25.2%, respectively, in comparison to the same percentage of untreated CR. The proposed approach demonstrates a viable pathway for integrating waste materials and SCM-based technologies to develop high-performance, sustainable cementitious composites. Full article

Accurately capturing muscle behavior remains a challenging task in computational biomechanics, primarily due to the nonlinear response, anisotropy, and time-dependent characteristics of muscle tissue. In this context, finite element methods have proven to be a suitable framework for representing such complex mechanical behavior. Among the available constitutive approaches, Hill’s three-element model continues to be widely adopted, largely because it offers a reasonable balance between physiological interpretability and computational efficiency. In this work, a parametric and sensitivity-oriented analysis of the Hill three-element muscle model is performed within a finite element formulation originally proposed by Kojić, Mijailović, and Zdravković (1998) and implemented in the PAK software environment. The analysis considers five key parameters, which are varied independently: the stiffness parameter of the series elastic element (α), the corresponding stress scaling parameter (β), the modulus of the parallel elastic element (E), the activation level (a), and the length ratio constant (k). To enable comparison between parameters of different physical nature, normalized sensitivity indices are used. The results show that the activation parameter a has the strongest influence on active force generation, with an increase of 36.4% at the highest considered activation level. In contrast, parameters α and β primarily affect the behavior of the series elastic component, with variations on the order of ±15–18%. It can also be observed that the influence of individual parameters depends on the deformation regime. At lower deformation levels, the response is mainly governed by the parameter E, while α and β become more relevant in the intermediate nonlinear range. At higher deformation levels, the activation parameter a becomes dominant. From a modeling perspective, these findings suggest a structured approach to parameter calibration in Hill-type finite element models. In addition, they provide further insight into the sensitivity characteristics of such formulations within computational biomechanics. Full article

This study proposes and validates a framework that integrates Grey Wolf Optimization (GWO) with Extreme Gradient Boosting (XGBoost) for estimating the Poisson’s ratio of auxetic structures. First, for 320 models derived from Computer-Aided Design-based (CAD-based) unit-cell designs, a systematic sweep of diameter and cellular dimensions was conducted to obtain porosity coverage in the 45–85% range. Subsequently, elastic modulus and Poisson’s ratio were computed via finite element analysis (FEA) at three mesh resolutions (0.20/0.25/0.30 mm), and relationships between design variables and outputs were examined using correlation heatmaps and Locally Weighted Scatterplot Smoothing (LOWESS) curves. GWO optimized the XGBoost hyperparameters through a multi-band narrowed search strategy; performance was evaluated using Mean Absolute Error (MAE), Root Mean Squared Error (RMSE), Mean Squared Error (MSE), and Coefficient of Determination ($R^2$) metrics, as well as residual diagnostics and Ground Truth–Prediction alignments for Poisson’s ratio. Across all configurations, $R^2\ge 0.994$ and absolute errors are on the order of ∼${10}^{-3}$; the 0.25 mm mesh stands out in terms of overall balance with the lowest squared-error profile and the highest $R^2$, the 0.30 mm mesh is practically equivalent in terms of MAE, and the 0.20 mm mesh is comparatively weaker. Residual diagnostics—comprising a pattern-free cloud around zero, slight right-skewness, and limited heteroskedasticity—indicate low bias and no substantive model-specification issues. The findings align with physical insight, confirming that Poisson’s ratio shifts toward more negative values as porosity increases and toward less negative values as diameter increases. The proposed GWO–XGBoost framework provides a reliable pre-screening tool for rapid design exploration and Poisson’s-ratio-targeted optimization, with the potential to reduce the need for additional FEA simulations and experimental iterations during early-stage design. Full article

This study developed high-oxygen-barrier active bilayer packaging films by combining corona-treated low-density polyethylene (LDPE) with chitosan/glycerol (CS/Gl) and carvacrol@natural zeolite (CV@NZ) nanohybrid layers using industrially scalable processes. LDPE film was surface-activated via ambient-pressure corona treatment (0.75 s/cm² at 45 kV, 30 W) and assembled with solution-cast CS/Gl or CS/Gl/CV@NZ monolayers via hot-pressing (110 °C, 1 min). Corona treatment enabled robust interfacial adhesion, evidenced by statistical equivalence between monolayer and bilayer mechanical properties. Incorporation of 10 wt.% CV@NZ nanohybrid increased elastic modulus by 60% (to ≈2970 MPa) and tensile strength by 30% (to ≈50 MPa). The LDPE-CS/Gl film achieved a 64-fold reduction in oxygen permeability; CV@NZ incorporation maintained excellent barrier performance (22-fold reduction). Antioxidant potency increased 16-fold upon CV@NZ incorporation. The LDPE-CS/Gl/CV@NZ film demonstrated exceptional antibacterial activity (5.08–5.30 log reductions; >99.999% kill) against both Listeria monocytogenes and Escherichia coli—substantially exceeding additive effects—confirming synergistic action between chitosan and carvacrol. In fresh minced pork preservation (8 days, 4 °C), the active film achieved a 1.73 log reduction in Total Viable Count (98.2% inhibition) and extended microbiological shelf life from 6 to beyond 8 days (33% increase). The bilayer configuration utilizes only 40% of the total thickness as biopolymer, aligning with circular economy principles. Unlike conventional high-barrier films (e.g., PA/PE) which require complex compatibilization for recycling, the water-soluble chitosan layer in this bilayer design can be readily separated from the LDPE backbone, enabling recovery of a pure polymer stream. This work demonstrates a feasible pathway for developing next-generation active packaging that combines a high oxygen barrier, potent antioxidant activity, and exceptional antimicrobial efficacy through industrially scalable manufacturing. Full article