Search Results (301)

To address the engineering challenge of durability deterioration in concrete structures in the cold and saline regions in northern China, this study investigated PVA fiber-reinforced concrete under combined sulfate attack and freeze–thaw cycles using PVA fiber volume fractions (0%, 0.1%, 0.3%, 0.5%) and salt-freeze cycles (0, 25, 50, 75, 100, 125, 150 cycles) as key variables. By testing the mechanical and microscopic properties of the specimens after salt-freeze, the degradation law of macroscopic performance and the evolution mechanism of microscopic structure of PVA fiber concrete under different volume fractions are analyzed, and the salt-freeze damage evolution equation is established based on the loss rate of relative dynamic elastic modulus. The results show that the addition of PVA fibers has no significant inhibitory effect on the surface erosion of concrete, and the degree of surface spalling of concrete still increases with the increase in the number of salt-freeze cycles. With the increase in the number of salt-freezing cycles, the mass, relative dynamic elastic modulus and cube compressive strength of the specimens first increase and then decrease, while the splitting tensile strength continuously decreases. The volume fraction of 0.3% PVA fibers has the most significant effect on improving the cube compressive strength and splitting tensile strength of concrete, and at the same time, it allows concrete to reach its best salt-freezing resistance. PVA fibers contribute to a denser microstructure, inhibit the development of micro-cracks, delay the formation of erosion products, and enhance the salt-freezing resistance of concrete. The damage degree D of relative dynamic elastic modulus for PVA fiber concrete exhibits a cubic functional relationship with the number of salt-freeze cycles N, and the correlation coefficient R² is greater than 0.88. The equation can accurately describe the damage and deterioration law of PVA fiber concrete in the salt-freeze coupling environment. In contrast to numerous studies on single-factor exposures, this work provides new insights into the degradation mechanisms and optimal fiber dose for PVA fiber concrete under the synergistic effect of combined sulfate and freeze-thaw attacks, a critical scenario for infrastructure in cold saline regions. This study can provide theoretical guidance for the durability assessment and engineering application of PVA fiber concrete in cold and saline regions. Full article

To promote the sustainable utilization of desert sand as a regional resource in the infrastructure construction of saline-alkali areas, this paper proposes an accelerated test method based on the coupling of an external electric field (60 V) and a 2% Na₂SO₄ solution for rapid evaluation of its sulfate erosion resistance. The optimal mix proportion (FA 10%, water-to-binder ratio 0.33, cement-to-sand ratio 1:1.5, SF 10%) was determined through orthogonal experiments. By employing multi-scale analytical techniques including electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermal analysis (TG-DTG), the differentiated deterioration mechanisms driven by the electric field were systematically revealed. The results show that the charge-transfer resistance (Rct) decreased by about 95% within 28 d, demonstrating the characteristic of “micro-scale deterioration preceding macro-scale strength loss.” The anode region was dominated by dissolution of hydration products (porosity 5.1%), while the cathode region, due to enrichment of sulfate ions (S content 3.37 wt.%), generated a large amount of expansive products, leading to more pronounced structural damage (porosity 8.3%) and greater mass loss (cathode 12.56% > anode 9.85%). This study not only elucidates the deterioration mechanisms of desert sand concrete under coupled environmental action, but also provides a mechanism-explicit, rapid and efficient laboratory evaluation method for its sulfate resistance, offering practical guidance for durability design and prevention in engineering structures exposed to saline-alkali conditions. Full article

Irreversible erosion damage of the hearth lining determines the campaign life of a blast furnace (BF). Among the factors involved, structural thermal stress resulting from both internal and external temperature differences and external constraints is a key mechanism in the damage to the hearth lining. Based on a thermal–fluid–structural coupling model that accounts for molten iron flow and solidification, this study, building on thermal stress analysis of the hearth lining, proposes a method to determine the critical strength-based erosion boundary of the lining, using the compressive strength of carbon bricks as the criterion. It also investigates the influence of factors such as dead iron layer depth, tapping productivity, and molten iron temperature on the thermal stress-driven erosion boundary. The findings reveal that the depth of the dead iron layer determines the morphology of the hearth lining’s erosion. With increasing depth, the erosion pattern transitions from an elephant foot profile to a wide-face profile, while the radial erosion depth first increases and then decreases. Both increased tapping productivity and elevated molten iron temperature do not change the erosion shape but aggravate the erosion degree and induce axial displacement of the erosion zone. The research findings are of great significance for deepening the understanding of thermal stress damage in the hearth lining and provide an effective reference for long-term hearth design. Subsequent validation with a large amount of industrial data will further enhance the practical applicability of the proposed method. Full article

To enhance the operational damage resistance of hydraulic machinery, this study employed laser cladding technology to fabricate a Co_37.4Cr₃₀Ni₂₀Al₅Ti₅Nb_2.6 high-entropy alloy coating on 04Cr13Ni5Mo substrate. The influence of laser power on the microstructure and properties of the coating was systematically investigated. Based on preliminary research, the friction-wear performance and cavitation erosion behavior of the coatings prepared at 3000 W, 3200 W, and 3400 W were specifically examined. Results indicate that as the laser power increased from 3000 W to 3400 W, the microhardness of the coating gradually decreased from 345.3 HV_0.2. At 3000 W, the precipitation of trace strengthening phases significantly enhanced the mechanical properties. In wear tests under a 20 N load for 30 min, the wear rate of the coating prepared at 3000 W was 1.41 × 10⁻⁴ mm³/(N·m), which is 13.5% lower than that of the 3200 W coating (1.63 × 10⁻⁴ mm³/(N·m)) and 16.07% higher in wear resistance compared to the substrate. Cavitation erosion tests revealed that after 20 h of ultrasonic vibration, the mass loss of the 3000 W coating was only 2.35 mg, representing an 88.89% reduction compared to the substrate (21.15 mg), and significantly lower than that of the 3200 W (4.57 mg) and 3400 W (3.85 mg) coatings. This study demonstrates that precise control of laser power can effectively optimize the cavitation erosion resistance of high-entropy alloy coatings, providing technical support for their application in harsh environments. Full article

Concrete structures in western saline soil regions are subjected to extreme environments with coupled dry-wet cycles and high concentrations of erosive ions such as Cl⁻, SO₄²⁻, and Mg²⁺, leading to severe degradation of mechanical properties. This study employed a simulated accelerated, high-concentration solution (Solution A, ~8× seawater salinity) similar to the composition of actual saline soil to perform accelerated dry-wet cycling corrosion tests on ordinary C40 concrete specimens for six corrosion ages (0, 5, 8, 10, 15, and 20 months). For each age, three replicate cube specimens were tested per property. The changes in cube compressive strength, splitting tensile strength, prism stress–strain full curves, and microstructure were systematically investigated. Results show that in the initial corrosion stage (0–5 months), strength exhibits a brief increase (compressive strength by 11.87%, splitting tensile strength by 9.23%) due to pore filling by corrosion products such as ettringite, gypsum, and Friedel’s salt. It then enters a slow deterioration stage (5–15 months), with significant strength decline by 20 months, where splitting tensile strength is most sensitive to corrosion. Long-term prediction models for key parameters such as compressive strength, splitting tensile strength, elastic modulus, peak stress, and peak strain were established based on grey GM(1,1) theory using the measured data from 0 to 20 months, achieving “excellent” accuracy (C ≤ 0.1221, p = 1). A segmented compressive constitutive model that considers the effect of corrosion time was proposed by combining continuous damage mechanics and the Weibull distribution. The ascending branch showed high consistency with the experimental curves. Life prediction indicates that under natural dry-wet cycling conditions, the service life of ordinary concrete in this region is only about 7.5 years when splitting tensile strength drops to 50% of initial value as the failure criterion, far below the 50-year design benchmark period. This study provides reliable theoretical models and a quantitative basis for durability design and life assessment of concrete structures in western saline soil regions. Full article

Erosion of the leading edge is one of the most severe forms of damage in wind turbine blades, particularly in offshore wind farms. This degradation, mainly caused by rain, sand, and airborne particles through droplet impingement wear, significantly decreases blade aerodynamic efficiency and power output. Since blades, typically made of fiber-reinforced polymer composites, are the most expensive components of a turbine, developing protective coatings is essential. In this study, polyurethane (PU) composite coatings reinforced with titanium dioxide (TiO₂) particles were added on glass fiber substrates by spray coating. The incorporation of TiO₂ improved the mechanical and electrochemical performance of the PU coatings. FTIR and XRD confirmed that low TiO₂ loadings (1 and 3 wt%) were well dispersed within the PU matrix due to hydrogen bonding between TiO₂ –OH groups and PU –NH groups. The PU/TiO₂ 3% coating exhibited ~61% lower corrosion current density (I_corr) compared to neat PU, indicating superior corrosion resistance. Furthermore, uniform TiO₂ dispersion resulted in statistically significant improvements (p < 0.05) in hardness, yield strength, elastic modulus, and adhesion strength. Overall, the PU/TiO₂ coatings, particularly at 3 wt% loading, show strong potential as protective materials for wind turbine blades, given their enhanced mechanical integrity and corrosion resistance. Full article

The production of reliable turbo machinery, particularly gas turbine blades, is a major global challenge. This capability serves as a key indicator of a nation’s industrial base, technological prowess, and comprehensive strength. Critical components in aircraft engines and gas turbines operate under extreme conditions, including high temperatures, high pressures, and substantial mechanical stresses. Consequently, there is a growing urgency to develop cost-effective and time-efficient repair strategies to enhance engine performance and efficiency. However, many mission-critical parts, especially high-pressure (HP) blades, are prone to severe damage. Moreover, taking equipment offline for blade maintenance and repair is a time-consuming process. It is also highly costly to restore these essential components to full functionality. Since 1996, researchers have focused on applying laser metal deposition (LMD) additive manufacturing technology for high-performance repair and remanufacturing of aerospace engines and industrial gas turbine (IGT) blades. Empirical studies have demonstrated that depositing a high-quality, erosion-resistant protective coating on the leading edge of HP blades effectively extends the service life of turbine blades in both aircraft engines and industrial gas turbines. This study systematically outlines the technical workflow of the proposed methodology and provides a concise perspective on emerging development trends. Full article

A prediction methodology for the mid-span deflection of fatigue-damaged RC beams subjected to chloride-induced corrosion is proposed, incorporating the coupled effects of fatigue stress levels and localized pitting corrosion in steel reinforcement. The reliability of the methodology is validated through experimental comparisons. The effects of fatigue stress are quantified via two mechanisms: degradation of the concrete elastic modulus and the development of fatigue-induced cracks in the steel reinforcement, which reduces its effective cross-sectional area. Pitting corrosion is simplified as equivalent surface cracks. To determine the chloride concentration within the concrete cover for predicting steel pit depth, a 3D meso-scale model is developed to simulate chloride ingress in fatigue-damaged concrete. The concrete is treated as a three-phase composite composed of coarse aggregate, mortar matrix, and the interfacial transition zone (ITZ), and each phase has its own diffusion coefficient. Based on previous chloride concentration tests, the effect of fatigue loading is considered by the accelerated and depth-dependent diffusion coefficients. Based on the meso-scale simulation results, mid-span deflections of fatigue-damaged RC beams under varying chloride exposure durations are predicted. The findings conclusively demonstrate that, under prolonged chloride erosion, the mechanical stress state remains the predominant factor governing structural deformation, overshadowing time-dependent corrosion effects. Full article

According to statistics, between 1954 and 2021, China experienced 3558 dam failures in reservoirs, with flood overtopping accounting for 51.04% of these incidents. Once an earth-rock dam fails, it not only directly threatens the lives and property of surrounding residents and disrupts normal living order, but also damages infrastructure such as farmland, transportation, and power systems, resulting in enormous economic losses. To investigate the mechanisms of overtopping failure and breach evolution in homogeneous earthen embankments during flood seasons, this study conducted seven sets of laboratory model tests with the Changkai Embankment in Fuzhou City, Jiangxi Province, as a prototype. The tests considered various operational conditions, including different crest widths, embankment heights, channel water depths, and river flow velocities. The test results are as follows: Overtopping failure of earth embankments can be categorised into three distinct stages. The breach formation process can be categorised into three stages: vertical erosion (stage I), breach expansion (stage II) and breach stabilisation (stage III). River water levels and inflow rates were identified as pivotal factors influencing the final morphology of the breach and the flow velocity within it. Conversely, the height of the dike was found to have little influence on the shape of the breach and the flow velocity. The breach width ranges from 6 cm to 12 cm. An increase in water depth, corresponding to a greater difference in water levels on both sides of the river, has been observed to result in a deeper breach and faster widening rate. Elevated water levels have been shown to increase the potential energy of the water, which is subsequently converted into greater kinetic energy during breach formation. This, in turn, increases the flow velocity at the breach. However, a negative correlation has been observed between inflow velocity and flow at the breach. This paper combines the material properties of the embankment to discuss the overtopping failure mechanism and the breach evolution law of homogeneous earth embankments. This provides a basis for preventing and controlling embankment failure disasters. Full article

Leading-edge erosion (LEE) of wind-turbine blades, driven primarily by rain erosion, particulate erosion, and environmental ageing, remains one of the most pervasive causes of performance loss and maintenance cost in offshore and onshore wind farms. Self-healing coatings, which autonomously or semi-autonomously restore barriers and mechanical function after damage, promise a paradigm shift in blade protection by combining immediate impact resistance with in-service reparability. This review surveys the state of the art in self-healing coating technologies (intrinsic chemistries such as non-covalent interactions or dynamic covalent bonds; extrinsic systems including micro/nanocapsules and microvascular networks) and evaluates their suitability for anti-erosion, mechanical robustness, and multifunctional protection of leading edges. The outcomes of theoretical, experimental, modelling and field-oriented studies on the leading-edge protection and coating characterisation identify which self-healing concepts best meet the simultaneous requirements of toughness, adhesion, surface finish, and long-term durability of wind blade applications. Key gaps are highlighted, notably trade-offs between healing efficiency and mechanical toughness, challenges in large-area and sprayable application methods, and the need for standardised characterisation and testing of self-healing coating protocols. We propose a roadmap for targeted materials research, accelerated testing, and field trials. This review discusses recent studies to guide materials scientists and renewable-energy engineers toward promising routes to deployable, multifunctional, self-healing anti-erosion coatings, especially for wind-energy infrastructure. Full article

Cavitation erosion is a predominant failure mode of austenitic stainless steels in corrosive fluid environments, severely limiting their durability in nuclear piping and hydraulic components. In this study, five 316LN steels with 0.008–0.34 wt.% nitrogen content were fabricated, and both short-term (2 h) and long-term (24 h) cavitation tests were performed to elucidate the effect and mechanism of nitrogen. Increasing nitrogen markedly enhanced cavitation resistance: after 24 h, the cumulative mass loss decreased by 36%, 52%, 60%, and 71% for 09N, 17N, 22N, and 34N relative to 00N, accompanied by lower surface roughness, shallower pit depth, and a prolonged incubation stage. SEM revealed a progressive damage process from twin/high-angle grain boundaries to intragranular deformation bands and finally to spalling at slip intersections, whereas high-N steels exhibited only slight local detachment. TEM demonstrated that nitrogen transformed dislocations from random networks into dense slip bands and planar arrays with stacking faults, raising hardness from ~140 HV to ~260 HV. EBSD further confirmed strain-induced martensite transformation under severe deformation, providing additional strengthening. These results reveal that nitrogen improves cavitation resistance by tailoring dislocation structures and enhancing strength–plasticity compatibility, offering guidance for the design of high-performance austenitic stainless steels in cavitation environments. Full article

Sediment-laden seawater (1.4 kg/m³) under controlled flow velocities (1.5 m/s and 3.0 m/s) was employed to evaluate degradation mechanisms in static anti-fouling coatings. Exposure to 1.5 m/s sediment-laden flow induced a 49% reduction in adhesion strength, a 4.9–5.2° decrease in water contact angle, and an elevation in surface roughness from 0.32 μm to 0.88 μm after 30 days. Concurrently, antibacterial rate and anti-algal rate declined by 11.9% and 14.6%, respectively. In comparison, pure seawater scouring at equivalent velocity reduced adhesion by 30% and contact angle by merely 1.1°. Low-flow (1.5 m/s) conditions accelerated abrasive wear, driving severe surface roughening, whereas higher flow velocity (3.0 m/s) disrupted sustained particle–coating contact through turbulence generation, attenuating roughness progression. Crucially, low-flow conditions intensified abrasive wear and promoted severe surface roughening, whereas higher flow velocities generated sufficient turbulence to disrupt sustained particle–coating contact, thereby slowing the progression of roughness. These findings reveal a previously unrecognized, flow-velocity-dependent erosion mechanism: lower velocities encourage particle deposition and progressive surface damage, while higher velocities unexpectedly produce a protective, turbulence-mediated buffering effect that mitigates surface roughening. These findings establish a theoretical foundation for developing advanced anti-fouling coatings with enhanced resistance to sediment erosion. Full article

The oil and gas sector encounterssignificant material problems during acid stimulation, particularly under high temperatures, high pressures, and corrosive conditions with CO₂ and H₂S. This study focused on corrosion and erosion failures of tungsten carbide jetting nozzles in coiled tubing bottom hole assemblies. While tungsten carbide is durable, its high price, restricted machinability, and scarcity necessitate the search for viable alternatives. This study sought to identify and validate a low-cost, readily available, and easily machinable alloy with equivalent performance. A rigorous material selection approach took into account thermochemical stability, mechanical strength, and corrosion resistance under simulated downhole circumstances. Candidate alloys, both coated and uncoated, were subjected to extensive laboratory testing, including acid compatibility, high-temperature corrosion, erosion resistance, and mechanical integrity assessments. The majority failed due to pitting or surface deterioration. However, one coated alloy system was very resistant to chemical and thermal damage. To support long-term performance, a machine learning model relying on Gradient Boosting was created to forecast corrosion behavior using operational factors; demonstrating effective prediction characteristics compared with four other models. This AI-powered tool allows for accurate prediction of corrosion risks and aids decision-making by determining whether the material will maintain integrity under harsh acidic conditions. Field tests proved the selected alloy’s durability and jetting efficiency during many acid stimulation cycles. The corrosion and wear performance of coated 4145 material demonstrates a validated, cost-effective alternative to tungsten carbide with only four times lower corrosion resistance than carbide, outperforming other alloy combinations with up to 35 times higher corrosion rates. These results reveal tremendous opportunities for improving material design in corrosive energy applications. Full article

This study aims to resolve the “secondary activation” challenge when erecting structures over goaf zones by employing a novel grouting and filling material. It delves into the performance degradation of the innovative ECS soil grouting filling material (ESGF material) within the goaf’s ionic erosion context. Erosion tests were performed on ESGF material specimens with varying mix designs to mimic the sulfate and chloride erosion scenarios commonly encountered in practical engineering. The macro-mechanical properties and microstructural changes of ESGF materials under ionic erosion environment were systematically investigated by various testing methods, such as unconfined compressive strength (UCS), SEM, XRD, TG, FTIR, and Raman. The findings indicate that both sulfate and chloride erosion lead to a reduction in the strength of the ESGF material. As erosion progresses, the specimens experience a mass increase followed by a decrease, with their strength exhibiting a consistent downward trend. In sulfate erosion conditions, the buildup of expansion product like ettringite (AFt) and thaumasite (TSA) inflicts substantial internal structural damage. Conversely, Friedel’s salt, the primary product of chloride erosion, exhibits relatively weaker expansiveness, and chloride concentration exerts a less pronounced effect on material degradation. Moreover, the cementitious material content and the proportion of quick-setting component play a significant role in determining the ESGF material’s resistance to erosion. By adjusting the quick-setting components ratio in response to changes in the water content of soft soil, the anti-ion erosion performance of solidified soil can be effectively enhanced. Notably, curing with a 5% sulfate maintenance could significantly improve the erosion resistance of ESGF material. This suggests that ESGF materials can be used without concern for curing issues in high-salinity environments during grouting. The research addresses the root cause of goaf subsidence while facilitating the recycling of solid waste, offering an environmentally friendly solution. Full article

Inflammatory bowel diseases (IBDs), including Crohn’s disease (CD) and ulcerative colitis (UC), are chronic immune-mediated disorders characterized by mucosal injury, cycles of inflammation and repair, and tissue damage. Persistent inflammation accelerates epithelial turnover, generates oxidative and replication stress, and remodels the stromal niche, contributing to the risk of colorectal cancer (CRC). Systematic dysplasia surveillance remains essential. Cellular senescence has emerged as a unifying mechanism linking inflammation, impaired epithelial repair, fibrosis, and neoplasia. In UC, p16/p21 upregulation, telomere erosion, and loss of lamin B1 accumulate and adopt a senescence-associated secretory phenotype (SASP) that perpetuates barrier dysfunction. In CD, senescence within stem and stromal compartments limits regeneration, promotes pro-fibrotic remodeling, and sustains cycles of injury and repair via chronic SASP signaling. IBD prevalence continues to rise from environmental factors, dietary changes, antibiotic exposures, and gut microbiota alterations. Pathogenesis integrates genetic factors (e.g., NOD2, IL23R, HLA, and ATG16L1 mutations), environmental modifiers, dysbiosis characterized by loss of short-chain fatty-acid-producing Gram-positive bacteria and expansion of Proteobacteria, and a dysregulated immune system. Therapeutic strategies have shifted toward targeted biologics and small molecules to promote mucosal healing. In this review, we recapitulate the mechanistic axes of inflammation, oxidative stress, and senescence in IBD and then critically evaluate emerging targeted therapies. Topics include anti-TNFα, integrin blockade, IL-12/23 and IL-23 inhibition, JAK inhibitors, S1P receptor modulators, microRNA modulation, senomorphics, mesenchymal cell therapy, and microbiome interventions. We endorse biomarker-guided therapy and propose future directions to break the SASP-driven inflammatory loop and mitigate long-term carcinogenic risk. Full article