Search Results (6,457)

Corrosion of reinforcing steel is a key cause of deterioration in reinforced concrete (RC) structures exposed to coastal environments with chloride presence. The loss of reinforcing steel cross-sectional area, cracking of the concrete cover, and reduction in confinement progressively decrease both strength and ductility of structural elements. This study provides a reproducible, open-access dataset, compiling input parameters and numerical results of the cyclic behaviour of isolated RC columns and RC frames, specifically addressing their nonlinear cyclic response under moderate corrosion (η < 25%), as well as in the non-corroded (baseline) conditions, generated through conventional nonlinear modelling. In terms of modelling, the methodology applies fibre-section modelling for columns and concentrated plastic hinges for beams. Furthermore, the corrosion effects are incorporated by reducing the steel area and ultimate strain, while also accounting for the decrease in compressive strength of the cracked concrete cover. Therefore, the cyclic response is represented by a Pivot-type hysteretic model. It is worth noting that the dataset provides model input information, such as material stress–strain relationships and backbone curves reflecting corrosion-induced deterioration. It also includes structural outputs, such as force–displacement relationships, and envelopes of quasi-static hysteretic cycles for the analyzed columns and frames. Overall, the dataset facilitates the calibration and validation of numerical models for RC structures affected by corrosion. In conclusion, the contribution enhances the reliability of computational simulations and supports the development of predictive tools for structural performance under degradation scenarios. Full article

This review comprehensively examines the incorporation of nanoparticles (NPs) into biopolymers for 3D printing in biomedical applications, integrating material design, processing strategies, and translational considerations within a unified framework. Different types of NPs are analyzed regarding their effects on mechanical reinforcement, rheological modulation, and structural organization of biopolymeric matrices. The discussion covers principal additive manufacturing technologies, including extrusion-based systems such as fused deposition modeling (FDM) and direct ink writing (DIW), vat photopolymerization, powder-bed fusion (SLS), and emerging in situ nanoparticle formation approaches, emphasizing how nanoparticle loading and surface functionalization govern yield stress, shear-thinning behavior, viscoelastic recovery, and dimensional fidelity while mitigating agglomeration and optimizing interfacial interactions. Comparative evaluation of compressive modulus, strength, toughness, crystallinity, and porosity establishes structure–property–processing relationships directly linked to printability and functional performance. Biomedical applications are addressed in tissue engineering, biosensing, controlled and targeted drug delivery, and bioimaging, highlighting the balance between bioactivity and manufacturability. Finally, critical challenges—including compatibility, reproducibility, biological safety, long-term stability, regulatory adaptation, and environmental impact—are discussed, alongside future perspectives focused on green nanomaterials, AI-driven predictive formulation design, and digital twins for real-time monitoring and quality control in nano-enabled additive manufacturing. Full article

Cement-based grouts used in anchorage engineering often suffer from insufficient flowability, bleeding, and inadequate early-age strength, which may impair grout filling quality and interfacial bonding. This study investigated the synergistic use of fly ash (FA) and metakaolin (MK) to optimize the fresh properties, strength development, microstructure, and early-age anchorage performance of cement-based grouts. Rheological behavior, bleeding rate, and compressive strength were evaluated for grouts with different FA and MK contents, and the overall performance was ranked using the entropy-weighted TOPSIS method. X-ray diffraction and scanning electron microscopy were further employed to clarify the underlying microstructural evolution, and laboratory pull-out tests were conducted to verify the early-age anchorage effectiveness of the selected optimal mixtures. The results showed that the optimal performance was achieved at 15–20% FA and 3–6% MK. Within this range, grout viscosity decreased from 0.24 to 0.16 Pa·s, bleeding rate decreased from 13% to 2%, and compressive strength increased markedly at both 7 and 28 days. The optimized grout also increased the peak interfacial shear stress from 0.440 to 0.978 MPa. These improvements were associated with accelerated hydration, reduced CH and residual clinker phases, and a denser hydration-product network. The pull-out specimens failed predominantly along the grout–rock/soil interface, and the improved anchorage response was attributed to a denser hydration-product network that reduced pores and interfacial defects and promoted more efficient shear-stress transfer. Full article

Operando mechanical behavior of lithium-ion batteries under aggressive conditions remains insufficiently quantified, especially under combined high-rate and deep-discharge operation. This study investigated strain evolution in a commercial 18650 NMC lithium-ion cell using surface-mounted fiber Bragg grating sensors across 20 sequential conditions combining five discharge rates (1–4.5 C) and four cutoff voltages (2.5–1.0 V). All tests were performed on a single cell using identical 0.5 C constant-current constant-voltage charging, followed by a 2 h rest period and controlled discharge, to systematically evaluate mechanochemical evolution with increasing electrochemical severity. Maximum tensile strain during charging ranged from 45 to 59 µε and showed limited sensitivity to discharge severity. In contrast, discharge behavior exhibited clear rate- and cutoff-dependent transitions from tensile to compressive deformation; the most severe condition (4.5 C, 1.0 V cutoff) produced a peak compressive strain of about −27 µε and the most negative residual strain after relaxation. Although temperature increased monotonically with C-rate, strain evolution was nonlinear and non-monotonic, indicating that electrochemically induced stress dominated over thermal expansion alone. These findings reveal progressive amplification of irreversible deformation under severe discharge and demonstrate the value of fiber Bragg grating sensing for operando assessment of electrochemical–mechanical coupling in cylindrical lithium-ion cells. Full article

Proximal femoral fractures associated with osteoporosis are an important clinical problem, yet how bone quality independently influences stress distribution remains insufficiently understood. This study aimed to quantitatively compare surface stress distribution between normal and osteoporotic proximal femoral models using thermoelastic stress analysis (TSA). Fourth-generation composite femurs with identical external geometries were subjected to cyclic compressive loading at a 9° adduction angle, with different maximum loads applied to avoid structural failure (normal: 1900 N; osteoporotic: 1000 N). TSA was performed using an infrared lock-in system to obtain surface stress maps, and stress values were evaluated across key proximal regions and along the medial and lateral cortices. The osteoporotic group showed higher maximum stress values in the medial neck (−37.79 vs. −11.52 MPa), lateral neck (24.70 vs. 8.75 MPa), and intertrochanteric crest (−17.98 vs. −6.05 MPa), corresponding to approximately 1.8–3.5-fold increases compared with the normal model values normalized to 1000 N. Mean stress values were also higher by approximately 1.9–2.4-fold across regions. These results suggest that reduced bone quality is associated with increased proximal stress concentration. They may also help guide implant and fixation strategies, including stem selection and fixation configuration, by identifying regions susceptible to stress concentration under different bone quality conditions. Full article

This study evaluates the performance of foamed geopolymer concrete (FGC) incorporating rigid polyurethane (PU) waste as a partial sand replacement and aluminum powder (AP, 1%) as a foaming agent. The mixtures were based on metakaolin, fly ash, and silica fume. Fresh and hardened properties were assessed, including workability, setting time, density, compressive strength, flexural strength, splitting tensile strength, elastic modulus, water absorption, porosity, gas permeability, and chloride ion penetration. Microstructural characteristics were examined using scanning electron microscopy (SEM). The results show that moderate PU incorporation significantly enhances mechanical performance. The optimal mixture (PU30) achieved a compressive strength of 47.25 MPa at 180 days, representing a 15.6% increase compared to the control. Flexural and splitting tensile strengths improved by 19.9% and 16.7%, respectively, while the elastic modulus increased by 33.8% to 0.95 GPa. These improvements are attributed to enhanced particle packing and more efficient stress transfer within the matrix. In contrast, higher PU contents (>30%) reduced mechanical performance due to increased total porosity and weakened interfacial bonding. Durability-related properties indicated that mixtures PU20–PU30 exhibited reduced permeability and optimized pore structure, characterized by lower pore connectivity. SEM observations confirmed a denser matrix with uniformly distributed pores at optimal PU levels. Additionally, the integration of Random Forest regression with GLCM-based texture analysis demonstrated strong capability in predicting mechanical properties from SEM images. Overall, the combined use of PU waste and AP enables the production of lightweight, structurally efficient, and sustainable FGC with improved mechanical and durability performance. Full article

The multi-cycle high-rate injection and production operations in Underground Gas Storage (UGS) facilities converted from depleted fracture-pore carbonate gas reservoirs induce complex rock–fluid interactions that threaten long-term integrity and performance. This study experimentally investigates the petrophysical responses of the Xiangguosi (XGS) UGS carbonate reservoirs in China using multi-cycle stress sensitivity tests, fines migration experiments, and water evaporation–salt precipitation analyses. SEM observations distinguish the contributions of crack closure and matrix compression to permeability evolution. Results show a sharp contrast in mechanical damage: high-quality rocks present negligible permanent deformation (<8% Young’s modulus reduction), whereas poor-quality rocks suffer catastrophic deterioration (>60%). Fines migration exhibits a three-stage behavior under cyclic flow, with water saturation significantly aggravating permeability impairment. A critical salinity threshold (220,000 ppm) is identified for the transition between drying-enhanced storage and salt plugging. Permeability declines sharply despite a slight porosity increase due to selective salt clogging of key pore throats, revealing a clear porosity–permeability decoupling. Salt deposition under movable water conditions can reduce UGS capacity by up to 1.45%. Reservoir heterogeneity, microfractures, karst structures, and initial petrophysical properties dominate the storage and flow space evolution. This work provides a predictive framework for optimizing injection–production strategies and improving the performance of complex carbonate UGS. Full article

Conventional maintenance models often neglect the impact of pre-existing rutting on sealcoat performance, particularly in high-temperature regions like Chongqing in China, where rut-related failures are common. Existing ruts impose geometric constraints that significantly alter stress redistribution within the new sealcoat layer, yet this constraint mechanism remains poorly understood due to limitations in laboratory observation. This study developed a mesoscopic AC16 + MS3 composite discrete element model to simulate the mechanical behavior of a sealcoat applied over a rutted pavement. To replicate real-world conditions, a constant pressure of 0.7 MPa, representing the standard tire ground pressure in JTG E20-2011, was applied at a temperature of 70 °C, reflecting extreme high-temperature stability limits. Virtual rutting tests and contact force chain analyses were conducted across varying existing pavement rut depths, including 0 mm, 3 mm, 6 mm, and 10 mm. The results indicate that existing ruts redirect stress transfer paths, causing vertical compressive force chains to densify within the rutted zone and tensile stress to concentrate at rut edges. Mastic-mastic contacts transmit over 65% of the load, identifying asphalt mortar as the primary load-transfer phase. Notably, a 10 mm existing rut depth induces a tensile vacuum zone at depths of 15–40 mm, disrupting the standard U-shaped stress distribution. These findings clarify how pre-existing geometries govern structural degradation, suggesting that maintenance in high-temperature regions must prioritize asphalt mortar performance to mitigate edge cracking and deformation. Full article

High-power impulse magnetron sputtering (HiPIMS) technology was used to deposit Ti-Nb-Cr films on Si (100) and 316L substrates by changing the peak power of the Ti-Nb-Cr target. Optical emission spectroscopy (OES) was used to study the effect of peak power on the ion atomic arrival ratio in front of the substrate. Experimental instruments such as an X-ray diffraction (XRD) device, scanning electron microscope (SEM), transmission electron microscope (TEM), nanohardness tester, ball-disk reciprocating friction machine, and electrochemical workstation were used to study the effects of the atomic arrival ratio of Ti, Nb, and Cr ions on the microstructure, mechanical properties, and corrosion resistance of Ti-Nb-Cr films. The results show that when the peak power is 67.84 kW, the ion atomic arrival ratio of Ti reaches 47.57%, the ion atomic arrival ratio of Nb reaches 39.41%, and the ion atomic arrival ratio of Cr reaches 10.6%. The ion atomic arrival ratio is doubled compared to the peak power of 51.04 kW. The films prepared at different peak powers all show diffraction peaks of the BCC structure. At high power levels, the TiNbCr films exhibit reduced residual compressive stress, although this may be accompanied by lower hardness and wear resistance. Full article

Asphalt pavement on rigid base (cement concrete) differs significantly from traditional granular base pavement. To investigate its mechanical behavior, a viscoelastic–viscoplastic damage constitutive model for asphalt mixtures is proposed and verified. A user-material subroutine (UMAT) is developed to implement the model, and a three-dimensional finite element model is established to analyze pavement responses under various working conditions. Key numerical results include the following: the asphalt layer primarily experiences compressive–shear failure, with peak shear stress (τ₁₂) reaching 141.6 kPa under rigid base conditions; emergency braking increases τ₁₂ to approximately 270.3 kPa, a 91% increase; increasing vehicle speed from 15 m/s to 35 m/s raises τ₁₂ by 36.7%; based on stress analysis alone, the recommended asphalt layer thickness is between 0.10 m and 0.14 m, as thickness beyond 0.10 m yields diminishing stress reduction. The findings provide references for performance prediction, structural design, and material development of asphalt pavement on a rigid base. Full article

The phenomenon of progressive failure, stress and wave velocity asynchrony in rocks can inform early warning approaches for rock stability. In this study, the Geotechnical Consulting and Testing Systems rock triaxial test system was used to investigate the compression failure of sandstone from the Ningtiaota mine under confining pressures of 0, 2, 5, and 10 MPa, with synchronous ultrasonic wave velocity monitoring. Based on Martin’s crack strain theory, the variation laws of mechanical and wave velocity response characteristics during progressive failure were obtained from two replicate tests per confining pressure. The results indicate that the normalized stress at peak wave velocity ${\sigma }_{v_{\max }^P}/{\sigma }_f$ ranges from 0.84 to 0.99, whereas the normalized strain ranges from 0.73 to 0.98. With increasing confining pressure, both the strain and stress differences between the peak wave velocity and the peak stress increase. Wave velocity change results from the combined action of effective stress (promoting velocity increase) and crack strain (leading to velocity decrease), causing the wave velocity peak to occur ahead of the stress peak. The normalized crack initiation stress ${\sigma }_{ci}/{\sigma }_f$ ranges from 0.55 to 0.68, and the normalized crack damage stress ${\sigma }_{cd}/{\sigma }_f$ ranges from 0.79 to 0.91, consistent with literature values for intact sandstones. With increasing confining pressure, the proportion of the compaction stage remains unchanged, while the stable crack propagation stage decreases, and the elastic and unstable crack propagation stages increase. The stress-normalized difference between the peak wave velocity and the damage variable protrusion point is approximately $0.1{\sigma }_f$, showing a slight decreasing trend with increasing confining pressure. Full article

Polypropylene (PP) biocomposites reinforced with Cornus sanguinea L. (CS) pruning-waste particles were investigated using a combined experimental mechanics and finite element (FE) validation framework to support model-based design with an under-utilized lignocellulosic feedstock. Two particle-size fractions (<100 µm, LF1; 100–250 µm, LF2) were produced by grinding and sieving and incorporated into PP at 5–20 wt% via melt compounding and compression molding. Tensile and three-point bending properties were measured in accordance with ASTM D638 and ASTM D790. PP exhibited a tensile strength of 23.63 ± 0.51 MPa and a tensile modulus of 868 ± 21 MPa. Incorporation of LF1 particles increased tensile modulus monotonically, reaching 1020 ± 137 MPa at 20 wt%, while tensile strength decreased with filler content; by contrast, the 20 wt% LF2 formulation showed a pronounced strength reduction to 16.30 ± 0.25 MPa, indicating a disadvantageous size–loading interaction. In flexure, strength was comparatively insensitive to reinforcement (PP: 39.5 ± 0.34 MPa; reductions typically ≤7%), whereas flexural modulus increased to 2152 ± 27 MPa (LF1) and 2110 ± 34 MPa (LF2). FE models calibrated using true stress–true plastic strain data accurately reproduced tensile responses across the full strain range and flexural behavior within the pre-contact-dominated regime, demonstrating the suitability of PP/CS biocomposites for stiffness-driven applications. Full article

Extreme hydrological events fundamentally alter sediment transport dynamics across grain, reach, and watershed scales, rendering classical equilibrium-based transport formulations inadequate. This review synthesizes recent advances in multiscale sediment transport modeling under highly unsteady and high-magnitude forcing conditions. At the grain scale, particle-resolved simulations demonstrate that sediment entrainment is governed by turbulence intermittency and transient force exceedance rather than mean bed shear stress thresholds, particularly when the hydrograph rise timescale (T_h) becomes comparable to particle response times (T_p). At the reach scale, non-equilibrium transport emerges when the unsteadiness ratio T_h/T_a∼O(1), where T_a is the sediment adaptation timescale representing the time required for sediment flux to adjust toward transport capacity. Under these conditions, pronounced hysteresis between discharge and sediment flux is observed, requiring relaxation-based transport formulations instead of instantaneous equilibrium laws. At the watershed scale, the sediment delivery ratio (SDR), defined as the ratio of sediment yield at the basin outlet to total hillslope erosion, becomes highly time-dependent. Extreme precipitation events can activate hillslope-channel connectivity, increasing SDR by orders of magnitude relative to baseline conditions. A unified dimensionless scaling framework is presented based on mobility intensity (θ/θ_c, where θ is the Shields parameter and θ_c is its critical value for incipient motion), unsteadiness ratio (T_h/T_a), and morphodynamic coupling (T_f/T_m, where T_f is the hydraulic advection timescale and T_m is the morphodynamic adjustment timescale). This framework enables classification of sediment transport regimes ranging from quasi-equilibrium to cascade-dominated states. The synthesis demonstrates that predictive uncertainty increases nonlinearly across scales due to timescale compression, threshold activation, and feedback between flow hydraulics and evolving morphology. Recent developments in hybrid physics-AI approaches show promise in improving predictive capability by enabling dynamic transport closures, surrogate modeling of computationally expensive microscale processes, and data assimilation for real-time forecasting. However, these approaches remain limited by extrapolation uncertainty and the need to enforce physical constraints. Overall, this review concludes that regime-aware multiscale coupling, combined with uncertainty quantification and adaptive modeling strategies, is essential for robust sediment hazard prediction and climate-resilient infrastructure design under intensifying hydrological extremes. Full article

This study presents an analytical framework for evaluating the admissibility of biaxial inclination of rectangular sinking wells. The inclination of the well is interpreted as an eccentric transfer of the vertical load to the concrete plug, which produces a two-dimensional linear stress field beneath the base. Closed-form expressions are derived for the stresses at the four corners of the rectangular base as functions of the eccentricity components associated with the two orthogonal tilt directions. Based on these expressions, the admissibility of inclination is represented by a tilt envelope in the space of the two tilt angles, defining the combinations of tilt components that satisfy the adopted serviceability criterion. The analytical formulation also allows for comparison between the stress-based admissibility limit, the geometric condition corresponding to loss of compressive contact beneath the base, and a simplified indicator of lateral wall-pressure asymmetry acting on the shaft. Parametric analyses show that biaxial inclination leads to stress concentration at the corners of the base and that even relatively small tilt components may combine to produce significant stress amplification. The geometry of the well strongly influences the shape of the admissible tilt envelope, with elongated rectangular wells exhibiting directional anisotropy of the allowable inclination. The proposed analytical approach provides a transparent tool for evaluating inclined wells using basic geometric parameters in engineering practice. Full article

To address the stability challenges of surrounding rock in large-span open-off cuts within weakly cemented strata of western China, this study investigated the 1219 open-off cut at the Shila Wusu Coal Mine. An analytical elastic model for rectangular roadway stress was developed using complex variable function theory to examine the influence of the lateral pressure coefficient on stress distribution. Furthermore, numerical simulations were employed to characterize plastic zone evolution and evaluate support effectiveness. The results demonstrate that the lateral pressure coefficient significantly dictates the stress field: circumferential stress at the ribs intensifies with the increasing lateral pressure coefficient, while stress in the roof and floor decreases accordingly. Notably, tensile stresses develop in the roof and floor when the lateral pressure coefficient is less than 1. Stress extremes are concentrated at the roadway shoulders, exhibiting a distribution pattern where the ribs experience higher concentration than the roof and floor. The circumferential stress concentration coefficient exhibits a marked positive correlation with the lateral pressure coefficient. Numerical results indicate that post-support compressive stress at the shoulders reaches 39.24 MPa, with plastic zone widths of 1.64~2.06 m at the ribs, 2.70 m at the roof, and a significant 5.33 m at the floor, highlighting a pronounced risk of floor heave. Field loosening zone measurements of 1.08 m in the roof and 2.49 m in the rib align closely with numerical findings, confirming that the implemented support effectively constrains plastic zone development. By integrating theoretical derivation, numerical modeling, and in situ observations, this study establishes a robust theoretical and technical framework for the support design of large-span roadways in similar geological settings. Full article