Search Results (16,950)

Fe-Mn-Al-C lightweight steel is an alternative to traditional low-alloy structural steels. It is lightweight and can be used to reduce the weight of structures without increasing their density. However, in the marine environment, traditional low-alloy structural steels can be damaged by chloride ions, which shortens their service life. We do not yet understand how aluminum, an important alloying element in lightweight steel, affects the process of corrosion. In this study, we examined Fe-Mn-Al-C lightweight steels with different amounts of aluminum. We used full-immersion simulated marine corrosion tests and multi-dimensional characterization techniques, such as microstructure observation and electrochemical measurements, to explore the relationship between aluminum content and the steel’s corrosion rate, corrosion product structure, and corrosion resistance. The results showed that, compared with CS, the weight loss and rate of corrosion of steels that contain aluminum were a lot lower. While the corrosion rate of CS is approximately 0.068 g·h⁻¹·m⁻², that of 7Al steel is reduced to 0.050 g·h⁻¹·m⁻². The stable phases α-FeOOH and FeAl₂O₄ are formed in the corrosion products when Al is added. As the Al content increases, so does the relative content of these phases. Furthermore, FeAl₂O₄ acts as a nucleation site that refines corrosion product grains, reduces pores and cracks, and significantly improves the compactness of corrosion products. It also forms a dense inner rust layer that blocks the penetration of corrosive ions such as Cl⁻. This study confirmed that aluminum improves the corrosion resistance of steel synergistically by regulating the structure of the corrosion products, optimizing the phase composition, and improving the electrochemical properties. The optimal aluminum content for lightweight steel in marine environments is 7%, within a range of 5–9%. Full article

Conductive hydrogels show great promise for wearable sensors but suffer from low sensitivity in small strain ranges. In this study, we developed a micropatterned composite hydrogel sheet (thickness: 1.2 ± 0.1 mm) by constructing a continuous electronic conductive network of carbon nanotubes (CNTs) on a highly crosslinked micropatterned hydrogel sheet. The sheet was fabricated via a two-step synthesis of a polyvinyl alcohol/polyacrylic acid polymer network—crosslinked by Zr⁴⁺ in a glycerol-water system—using sandpaper as the template. The first step ensured tight conformity to the template, while the second step preserved the micropattern’s integrity and precision. The reverse sandpaper micropattern enables secure bonding of CNTs to the hydrogel and induces localized stress concentration during stretching. This triggers controllable cracking in the conductive network, allowing the sensor to maintain high sensitivity even in small strain ranges. Consequently, the sensor exhibits ultra-high sensitivity, with gauge factors of 76.1 (0–30% strain) and 203.5 (30–100% strain), alongside a comfortable user experience. It can detect diverse activities, from subtle physiological signals and joint bending to complex hand gestures and athletic postures. Additionally, the micropatterned composite hydrogel sheet also demonstrates self-healing ability, adhesiveness, and conformability, while performing effectively under extreme temperatures and sweaty conditions. This innovative structure and sensing mechanism—leveraging stress concentration and controlled crack formation—provides a strategy for designing wearable electronics with enhanced performance. Full article

The study aims to assess the potential of recycled carbon fibers recovered from end-of-life wind turbine blades as a sustainable reinforcement material for concrete and to establish correlations between fiber parameters and the mechanical behavior of fiber-reinforced concrete. The research focuses on how fiber length, content, and cement type affect the residual flexural strength and cracking behavior of FRC. The experimental program included 48 concrete mix series with varying fibre lengths (25, 38, and 50 mm), dosages (0, 2, 4, and 8 kg/m³), cement types (CEM I 42.5 and CEM II 42.5R/A-V), and water-to-cement ratios (0.50 and 0.40). Mechanical properties such as compressive strength, tensile strength, modulus of elasticity, and residual flexural strength were evaluated. Notched beams underwent three-point bending tests, and the progression of cracks was tracked using the digital image correlation method. The analysis revealed that enhancing both the fiber content and length generally bolstered the toughness and post-cracking characteristics of concrete, with a notable effect observed for fibers ranging from 38 to 50 mm in length when used at a dosage of 8 kg/m³. However, the effects depend on the fiber recovery technology and the base concrete strength, which may influence the results and should be considered as a limitation of this study. Full article

The research empirically evaluates ancient earth construction techniques through the analysis of archaeological adobe samples from Tell Zurghul/Nigin, south-eastern Iraq, dating from the mid-5th to mid-3rd millennium BCE. Simple, non-standardised empirical field tests were employed to obtain preliminary material characterisations, valuable for pilot assessments and gaining further significance when compared with quantitative analytical results. Their application evaluates the functionality of these tests while integrating archaeological insights with material science, underscoring the importance of multidisciplinary collaboration in earthen heritage conservation. Sixteen samples—fifteen archaeological and one modern—were analysed to assess raw material composition, grain size, clay behaviour, organic content, cohesion in wet and dry states, and surface adhesion. Results demonstrate notable homogeneity in material composition across the time span, primarily fine sands with minimal clay or silt. This suggests favourable drainage, minimal shrinkage, and reduced cracking but limited cohesion, implying a potential need for stabilisers such as plastic clays or fibres in construction. These findings inform conservative strategies for the preservation and restoration of earthen structures at the site. Full article

Two Ni-AlSi12 coatings were prepared using mechanical alloying (MA) and mechanical alloying followed by laser cladding (LC), respectively. Phase composition and microstructure variations caused by powder weight ratio and laser-specific energy were thoroughly analyzed in this study. Mechanical properties and oxidation behavior are markedly improved by subsequent laser cladding. The MA-LC coating, characterized by high densification and crack-free properties, presents a homogeneous microstructure with refined features. Microhardness testing reveals a marked superiority of the MA-LC coating over the conventional MA coating. The nano-hardness of MA-LC coating is 9.79 GPa, exhibiting that it is 6.84 times the nano-hardness of the MA sample. Owing to metallurgical bonding, the MA-LC coating possesses excellent scratch bonding performance. The MA-LC coating shows favorable oxidation behavior, due to the following three reasons: Firstly, oxygen diffusion can be effectively blocked by the compact Al₂O₃ oxide layer developed on the MA-LC coating surface, which reduces the oxidation velocity. Secondly, the coating’s mean grain dimensions demonstrate an increasing tendency after oxidation, which reduces the grain boundary serving as the oxygen diffusion channel. This enhancement significantly improves the coating’s oxidation resistance. Thirdly, analysis of the coating’s respective kernel average misorientation (KAM) map revealed a significant release of internal stress following 100 h oxidation, which can improve the coating’s resistance to spallation. Full article

Although low-silicon Al-Si alloys have been extensively studied, further improvement in their mechanical performance remains a critical challenge. This study examines the synergistic effects of scandium (Sc) and zirconium (Zr) additions on the solidification behavior, microstructural evolution, and mechanical properties of Al-5Si-Cu-Mg alloys. The Sc/Zr additions refine the α-Al grains and modify the eutectic Si morphology, with the most uniform microstructure obtained at 0.5 wt.% due to the formation of coherent Al₃(Sc,Zr) dispersoids. These additions also suppress the formation of needle-like β-Al₅FeSi phases and promote the transformation to compact α-Al₁₅(Fe,Mn)₃(Si,Zr,Sc)₂ intermetallics, optimizing the solidification process. The yield strength increases with Sc/Zr content owing to grain-boundary and precipitation strengthening. However, the alloy without Sc/Zr exhibits the highest ultimate tensile strength and elongation, likely due to its finer secondary dendrite arm spacing and the absence of casting-induced cracks in this investigation. Although Sc/Zr additions of 0.25–0.5 wt.% contribute to microstructural refinement, the concurrent formation of porosity and coarse intermetallic compounds leads to a deterioration in ductility. Excessive Sc/Zr additions further coarsen grains and degrade the overall mechanical integrity. Full article

Sustainable management of Construction and Demolition Waste (CDW) is key to the Circular Economy. Reusing crushed concrete as recycled concrete aggregates (RCAs) in hot-mix asphalt (HMA) is a viable CDW solution, although RCA’s high absorption can affect performance. This study evaluates the effect of partially replacing 0%, 10%, and 30% of virgin aggregate with RCA in a dense-graded HMA, assessing its moisture susceptibility and cracking resistance. Specimens were subjected to long-term water-immersion aging (3 and 6 months at 25 °C) and tested for Indirect Tensile Strength (ITS), Tensile Strength Ratio (TSR), and Cracking Tolerance Index (CT-index). RCA incorporation consistently increased ITS at all aging levels. In particular, the 30% RCA mixtures exhibited the highest strength, exceeding the absolute ITS thresholds required by various U.S. transportation agencies to ensure structural capacity. While TSR values remained below the 80% AASHTO T 283 threshold, 10% and 30% RCA mixes had higher TSR than the control, indicating a comparative improvement in moisture resistance. Conversely, the CT-index decreased with more RCA and longer immersion, particularly at 30% RCA, revealing a trade-off between strength gain and cracking tolerance under prolonged wet exposure. Overall, a 10% RCA replacement level provided the most balanced performance, supporting its technical feasibility for sustainable, performance-based mixture design. Full article

A comprehensive numerical investigation of Fatigue Crack Growth (FCG) under negative stress ratios (R < 0) was conducted using the Finite Element Method (FEM) and the ANSYS Benchmark 19.2 SMART crack growth module on modified Compact Tension (CT) specimens. This study addresses the critical challenge posed by the compressive portion of cyclic loading, which traditional Linear Elastic Fracture Mechanics (LEFM) models often fail to capture accurately due to the complex interaction of crack closure and reversed plastic zones. The analysis focused on the evolution of the von Mises stress and maximum principal stress distributions at the crack tip across a range of stress ratios, including R = 0.1, −0.1, −0.2, −0.3, −0.4, −0.5, and −1.0. The results demonstrate a significant inverse correlation between fatigue life cycles and the magnitude of the negative stress ratio, consistent with the detrimental effect of increasing tensile stress. Crucially, the numerical simulation successfully captured the non-monotonic behavior of the crack tip stress field, revealing that the compressive load phase substantially alters the effective stress intensity factor range and the crack growth path, which was governed by the Maximum Tangential Stress (MTS) criterion. This research provides a validated computational methodology for accurately predicting FCG life in engineering components subjected to demanding, fully reversed, or compressive–dominant cyclic loading environments. Full article

Intelligent crack detection and displacement measurement are critical for evaluating the health status of dams. Earth-fill dams, composed of fragmented independent material particles, are particularly vulnerable to climate changes that can exacerbate cracking and displacement. Existing crack segmentation methods often suffer from discontinuous crack segmentation and misidentification due to complex background noise. Furthermore, current skeleton line-based width measurement techniques demonstrate limited accuracy in processing complex crack patterns. To address these limitations, this study introduces a novel three-step approach for crack detection in earth-fill dams. Firstly, an enhanced YOLOv8-CGA crack segmentation method is proposed, incorporating a Cascaded Group Attention (CGA) mechanism into YOLOv8 to improve feature diversity and computational efficiency. Secondly, image processing techniques are applied to extract sub-pixel crack edges and skeletons from the segmented regions. Finally, an adaptive skeleton fitting algorithm is developed to achieve high-precision crack width estimation. This approach effectively integrates the pattern recognition capabilities of deep learning with the detailed delineation strengths of traditional image processing. Additionally, dam crest displacements and crack zone strain field are measured via the digital image correlation (DIC) method. The efficacy and robustness of the proposed method are validated through laboratory experiments on an earth-fill dam model, demonstrating its potential for practical structural health monitoring (SHM) applications in a changing climate. Full article

The inherent brittleness and poor fracture toughness of diamond-like carbon (DLC) films significantly limit their long-term reliability in mechanical and tribological applications. Among various strategies to enhance toughness, doping with non-carbide-forming metals (e.g., Ag, Cu) has emerged as a highly effective approach due to their ductile properties and compatibility with carbon matrices. This review comprehensively examines the underlying toughening mechanisms induced by non-carbide metal doping in DLC films. We systematically analyze how metal incorporation influences film microstructure, stress state, and crack behavior throughout the entire lifecycle—from deposition to mechanical testing. Five primary toughening mechanisms are identified and discussed: (I) bombardment-induced compressive stress relaxation during film growth; (II) refinement of carbon atomic clusters and enhancement of grain boundary sliding; (III) inhibition of dislocation accumulation through moderated carbon atom repulsion; (IV) plastic deformation, crack bridging, and strain field relaxation at crack tips; (V) shear-induced stress relief via soft metal particles. Among these, Mechanism IV (ductile phase toughening) is identified as the dominant contributor, and their synergistic action can lead to orders of magnitude improvement in wear resistance and a significant increase in crack propagation resistance. Furthermore, the critical role of doping content is emphasized, revealing an optimal concentration range (e.g., ~10–15 at.% for Ag and Cu) beyond which toughness may deteriorate due to excessive boundary formation or hardness loss. This work provides a mechanistic framework for designing toughened DLC films and guides future efforts in developing high-performance, durable carbon-based coatings. Full article

Mining-induced subsidence has significantly altered the structure of the vadose zone in coal mining areas, where soil cracks act as preferential pathways controlling water infiltration and redistribution. In this study, a Hydrus-2D dual-domain seepage model incorporating geometric parameterization of cracks was developed to simulate water migration in the vadose zone of a typical subsidence area in the Ordos Basin. The model integrates field-measured crack geometry, soil texture, and rainfall characteristics to quantitatively analyze preferential flow formation under twelve combinations of crack width, soil type, and rainfall intensity. The results show that (i) crack width dominates preferential flow behavior, with wider cracks (≥5 cm) deepening the wetting front from approximately 107 cm to 144 cm within 120 h and sustaining high conductivity after rainfall; (ii) soil texture governs infiltration pathways, as sandy soils promote deeper wetting fronts (up to 99 cm, ~40% deeper than loam) and layered soils induce interface retention or “jump” infiltration; and (iii) rainfall intensity controls infiltration depth, with storm events producing wetting fronts more than four times deeper than those under light rain. Overall, this study demonstrates the feasibility and significance of integrating crack parameterization into vadose-zone hydrological modeling using Hydrus-2D, providing a quantitative basis for understanding rapid infiltration–migration–recharge processes and supporting ecological restoration and water resource management in arid and semi-arid mining regions. Full article

Wood is a renewable and sustainable environmentally friendly building material. With proper design, it can help buildings achieve lower carbon emissions. However, since wood is a flammable material, its combustion performance in fires has attracted attention. In modern timber structures, glulam is a widely used engineered wood product. Thus, in this paper, glulam specimens made of four kinds of commonly used soft-wood species were used to compare their combustion performance, and the cone calorimeter method was employed. The indicators including time to ignition, heat release rate per unit area, total heat release per unit area, specific extinction area per unit mass, mass of residue, yield of CO and yield of CO₂ were evaluated and compared. The results showed that all the glulam specimens would experience cracking wood and adhesive layer. The time to ignition and peak mass loss rate of the four softwood species in the study was positively correlated with their density. Among these species, Spruce exhibited the highest peak heat release rate and the highest peak CO₂ yield but lowest smoke production, while Douglas fir had a relatively late CO production time and the lowest mass loss percentage, Larch had the lowest heat release rate and total heat release. This study provides fundamental data for the selection of wood structural materials and for future research on wood flame-retardant treatments. Full article

Bronze materials are indispensable across numerous industries for enhancing the durability and performance of components, primarily due to their excellent tribological properties, corrosion resistance, and machinability. This study investigates the impact of different atmospheric conditions on the properties of WAAM (wire arc additive manufacturing) cladded bronze coatings on 09G2S steel substrate. Specifically, the research examines how varying atmospheres—including ambient air (N₂/O₂, no shielding gas), pure argon (Ar), carbon dioxide (CO₂), and 82% Ar + 18% CO₂ (Ar/CO₂) mixture—influence coating defectiveness (porosity, cracks, non-uniformity), wettability (manifested as uniform layer formation and strong adhesion), and the extent of intergranular penetration (IGP), leading to the formation of characteristic infiltrated cracks or “bronze whiskers”. Modern investigative techniques such as optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were employed for comprehensive material characterization. Microhardness testing was also carried out to evaluate and confirm the homogeneity of the coating structure. The findings revealed that the bronze coatings primarily consisted of a dominant, highly textured FCC α-Cu phase and a minor BCC α-Fe phase, with Rietveld refinement quantifying a α-Fe volume fraction of ~5%, lattice parameters of a = 0.3616 nm for α-Cu and a = 0.2869 nm for α-Fe, and a modest microstrain of 0.001. The bronze coating deposited under a pure Ar atmosphere exhibited superior performance, characterized by excellent wettability, a uniform, near-defect-free structure with minimal porosity and cracks, and significantly suppressed formation of bronze whiskers, both in quantity and size. Conversely, the coating deposited without a protective atmosphere demonstrated the highest degree of defectiveness, including agglomerated pores and cracks, leading to an uneven interface and extensive whisker growth of varied morphologies. Microhardness tests confirmed that while the Ar-atmosphere coating displayed the lowest hardness (~130 HV_0.1), it maintained consistent values across the entire analyzed area, indicating structural homogeneity. These results underscore the critical role of atmosphere selection in WAAM processing for achieving high-quality bronze coatings with enhanced interfacial integrity and functional performance. Full article

In situ physical coal fracturing is one of the key technologies for deep coal resource extraction, among which the liquid nitrogen cyclic freeze–thaw (LNCFT) technique demonstrates remarkable fracturing effects and promising application potential in physical coal breaking. To determine economically viable mining and coalbed methane (CBM) extraction cycles, this study builds on previous research and conducts a series of experiments to investigate the effects of different cold condition temperatures and freeze–thaw cycles on the mesoscopic surface structure and macroscopic mechanical properties of deep, water-rich coal-rock samples. A statistical damage constitutive model for saturated coal-rock under coupled freeze–thaw and loading, incorporating a damage threshold, was established to more accurately describe the damage patterns and mechanisms. The results indicate that lower cold condition temperatures lead to greater mesoscopic crack propagation, lower uniaxial compressive strength, and significantly reduced freeze–thaw failure cycles. Under −45 °C, saturated coal-rock samples experienced macroscopic failure after only 23 freeze–thaw cycles, which is 9 and 15 cycles fewer than those under −30 °C and −15 °C, respectively. Furthermore, measurements of wave velocities in three directions before and after testing revealed that freeze–thaw cycles caused particularly pronounced damage in the direction perpendicular to the bedding planes. Additionally, the established coupled statistical damage constitutive model provides a more accurate and intuitive analysis of the entire process from damage to failure under different cold conditions, showing that as the temperature decreases and freeze–thaw cycles increase, the coal-rock’s brittleness diminishes while plastic deformation and ductile failure characteristics are enhanced. In summary, for coal and CBM extraction using the LNCFT technique, it is recommended to extract gas once after approximately 35 cycles of liquid nitrogen injection. This study provides a theoretical basis for the application of liquid nitrogen cyclic freeze–thaw technology in deep coal fracturing. Full article

This study aims to present the results from the assessment of carbonation depth, corrosion, and compressive strength of real marine structures in a 49-year-old gas processing industry. The assessment was achieved through visual observations and non-destructive tests, including rebound hammer test, ultrasonic pulse velocity (UPV) test, and potential corrosion mapping, conducted in the field. Several cylindrical samples were also cored to test the concrete compressive strength and carbonation depth. The results were subsequently used to calculate the remaining load-bearing capacity of the structures. The observations and measurements showed that carbonation depth ranged from 0 to 63% of the concrete cover, and potential corrosion was at a low to medium level in areas where corrosion had not occurred, while the actual compressive strength is still above the design strength. Moreover, based on the UPV test, the pulse velocity of the concrete is around 3600 m/s, indicating a good concrete quality. Meanwhile, severe corrosion of reinforcing steel occurred locally and only at certain places, which caused a very significant reduction in the diameter and cracks as well as spalling of the concrete cover. The process further led to a significant reduction in the load-bearing capacity. Therefore, repairing and strengthening of the structures were proposed using epoxy resin with corrosion inhibitor, cementitious, polymer-modified repair mortar containing reactive micro-silica, Carbon Fiber Reinforced Polymer (CFRP) rods, and CFRP sheets. The proposed method can be applied to these structures and also serves as a reference for repairing and strengthening other structures experiencing the same issue. Full article