Search Results (17,971)

Accurate crack segmentation is critical for automated infrastructure inspection but remains challenging due to the inherent conflict between preserving fine-grained geometric details and modeling global semantic context. Existing deep learning approaches typically encode both requirements within a single hierarchical representation, leading to irreversible boundary degradation or fragmented predictions under complex backgrounds. To address this limitation, we propose DCDRNet, a detail–context decoupled network that explicitly separates geometry-sensitive and context-aware representations into parallel encoding streams. The Detail Encoder maintains high-resolution features to preserve thin crack boundaries, while the Context Encoder performs adaptive global reasoning to reinforce structural continuity. Their controlled interaction enables effective integration of local precision and long-range context without representational interference. Extensive experiments on three public crack segmentation benchmarks demonstrate that DCDRNet consistently outperforms state-of-the-art methods in accuracy and robustness, achieving superior performance especially on challenging datasets with thin and fragmented cracks. Moreover, DCDRNet delivers a favorable accuracy–efficiency trade-off, combining compact model size with near real-time inference speed, making it well-suited for practical deployment in real-world inspection scenarios. Full article

For the failure issue of the weak part of the safety end of the nuclear power pressure vessel connection, the J-integral method was used to test the fracture toughness of the weak part at the bottom of the dissimilar metal welded joints (DMWJs) of SA508-III and 316L in the temperature range of 25 °C to 320 °C, and the mechanism of temperature-induced crack instability and propagation was studied. The research results indicate that at all test temperatures, the position of the weld near the 316L steel is the failure site of the welded joint. The fracture toughness of the joint decreases with increasing temperature, with a maximum decrease of 42.0%. Analysis shows that as the temperature increases, the dislocation density decreases, the tensile strength decreases, and the yield strength ratio decreases, making it easier for secondary cracks to initiate near the crack tip, thereby accelerating the unstable propagation of cracks. At the same time, as the temperature increases, the number of twin crystals that can promote crack turning and prolong the crack propagation path decreases, the energy absorbed before fracture decreases, and the fracture toughness value decreases accordingly, further accelerating the unstable propagation of cracks. Full article

The changes in functional groups during in situ co-pyrolysis of tar-rich coal with wheat straw were systematically examined using synchrotron diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) coupled with thermogravimetric analysis (TGA). Dynamic changes in C=C, C-O, and C-O-C groups were monitored and assessed across 50–500 °C, complemented by thermogravimetric analysis to assess synergistic effects. It revealed that co-pyrolysis significantly alters the thermal cracking pathways of oxygenated structures, reducing the overall onset temperature by approximately 150 °C. Specifically, instead of maintaining thermal stability, co-pyrolysis promoted early structural aromatization and advanced the C=O decomposition onset by 50 °C compared to coal, achieving a remarkable functional group cleavage rate of 47%. Additionally, the C=C formation temperature was advanced by 150 °C. Furthermore, co-pyrolysis effectively suppressed the secondary structural transformations observed in biomass by limiting the relative accumulation of C–O–C structures to merely a 5% increase, compared to a 52% surge in wheat straw. Interestingly, while DRIFTS confirms facilitated localized bond cleavage and deoxygenation, TGA reveals a macroscopic negative synergy regarding overall weight loss. These findings provide profound insights into the complex radical interactions during co-conversion, offering a crucial theoretical basis for optimizing coal–biomass co-pyrolysis technologies. Full article

The compliant discharge of landfill leachate constitutes a pivotal factor for the effective implementation of integrated water resource management. Aged landfill leachate exhibits complex composition and an imbalanced carbon-to-nitrogen ratio. Electrocatalytic oxidation technology, as an efficient advanced oxidation process, demonstrates promising application potential. This study employed Ti/RuO₂–IrO₂ Anodes for the electrocatalytic oxidation treatment of aged landfill leachate. The removal efficiencies and variation patterns of chemical oxygen demand (COD), ammonia nitrogen, and total nitrogen at different current densities and reaction times were systematically investigated, along with an analysis of energy consumption and current efficiency. The degradation and transformation processes of organic matter were elucidated using Three-dimensional Excitation–Emission Matrix (EEM) Spectra. Fresh anodes and those used for 1000 h were characterized by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) to elucidate their failure mechanisms. The results demonstrate that electrocatalytic oxidation achieves efficient pollutant removal. At a current density of 1000 A/m² and a reaction time of 30 min, the effluent concentrations of ammonia nitrogen and total nitrogen satisfied the discharge standards, while COD complied with emission requirements after 60 min. The pollutant removal efficiencies were positively correlated with current density and reaction time. EEM analysis revealed that the electrocatalytic process effectively disrupts the structure of macromolecular organic matter, degrading it into smaller molecules and eventually achieving complete mineralization. Electrode characterization identified titanium substrate corrosion due to coating cracks and coating detachment as the primary causes of electrode failure. This study confirms the effectiveness of electrocatalytic oxidation technology for treating aged landfill leachate, and provides a theoretical foundation and technical support for its practical engineering application. The technology exhibits considerable theoretical significance and promising application potential in the treatment of landfill leachate. Full article

The fatigue behaviour of a 90° long radius elbow, which is adjacent to the feedwater nozzle in a BWR, was analyzed. The start-up and shutdown transients were considered. A thermo-mechanical finite element analysis was carried out to determine the stresses induced by thermal transients, considering the environmental conditions in the reactor feedwater pipe. In addition, the Palmgren–Miner methodology and the ASME B&PVC code fatigue curve were applied to evaluate the accumulated damage and service life of the component. Environmental correction factors were considered to estimate environmentally assisted fatigue. Reductions in fatigue life were observed. In the second part of this paper, a part-through thickness semielliptical crack was also postulated in the internal surface of the elbow. It was aligned along the axial direction at the crown zone. Its growth was modelled using the Paris equation, evaluating the risk of failure using fracture parameters. It was found that the vulnerable area is located on the inner surface of the elbow, due to the concentration of stress caused by the curved geometry. Failure assessment diagrams (FADs) were plotted. It was found that the crack depth is the main factor governing crack behaviour under the conditions studied. The results provide a methodology for assessing the integrity of pipes subjected to specific environmental and operating conditions. Full article

This study investigates early-age cracking in the inclined bottom slabs of a 37.6 m wide PK-section concrete box girder during winter cantilever construction. A numerical method considering non-uniform material property development based on equivalent age was established. The method was validated by synchronous temperature and strain monitoring. The validated program was then used to analyze cracking causes and optimization measures. Results indicated that 3 days after casting, the maximum difference in equivalent age exceeded 7 days. Differences in elastic modulus and strength reached 30% and 34%, respectively, showing significant material non-uniformity. The restraint from completed segments was the primary cause of cracking. The total stress at the crack location was 5.5 MPa, with a 95% cracking probability. The ratio of thermal to shrinkage stress was 3.6:1. In summer, both total stress and strength increased, resulting in a similar cracking probability. Reducing the placing temperature decreased thermal stress by 0.13 MPa/°C in both seasons but had little effect on shrinkage. A 3 °C reduction lowered the cracking probability by 5–15%. Adding prestressed tendons to the bottom slab reduced total stress to 3.2 MPa and cracking probability to 37%, significantly mitigating cracking risk. Full article

This study evaluates the mechanical performance and failure characteristics of concrete reinforced with corn fibers as a sustainable natural additive. Corn fibers were incorporated at 0.25%, 0.5%, and 1.5% by weight of cement, with a control mix used for comparison. All mixtures were prepared at a constant water–cement ratio and adjusted for workability using a high-range water-reducing admixture. Results indicate that fiber dosage significantly influences strength and fracture behavior. The 0.5% fiber content yielded the best performance, improving compressive and flexural strength by approximately 36% and 24%, respectively, and promoting enhanced crack control and ductile response. In contrast, excessive fiber addition reduced performance due to fiber clustering and higher pore content. This study confirms that properly proportioned corn fibers can enhance concrete properties while encouraging sustainable construction through the reuse of agricultural waste. SEM further indicated a denser and more refined microstructure in the fiber-modified matrix. An ANOVA analysis and Tukey’s HSD post hoc test were performed to assess the influence of corn fiber content on the compressive, flexural, and tensile strengths of concrete mixtures, revealing statistically significant effects. Overall, the results highlight the potential of corn fiber reinforcement to improve the short-term mechanical performance of concrete mixes. Full article

Rolling contact fatigue cracks at the contact surface between a wheel and rail are evaluated based on the results of an external inspection (visual inspection). We developed a rail damage assessment technique using a fast regional convolutional neural network deep learning-based image analysis framework. We collected rail specimens from in-service tracks and performed scanning electron microscopy to correlate surface damage with subsurface crack formation, including crack depth, length, and angle. This data was input into an artificial neural network (ANN) to assess internal crack conditions using visual information obtained from rail surface damage. The resulting model achieved an average accuracy of 94.9%, outperforming other algorithms. We integrated this model into a developed rail damage diagnosis app with deep learning that links field photographs with cloud-based big data to learn, quantitatively diagnose, and present the type and scale of rail damage. We examined the field applicability of the application at a rail damage site. The standard deviation of the rail damage diagnosis results was 0.2–1.5% between different users. Appropriateness of the rail damage assessment technique using the proposed ANN image analysis technique was verified experimentally. Consistent diagnosis results could be derived regardless of the inspector, minimizing human error. Full article

High-temperature Solid Oxide Fuel Cells (SOFCs) typically operate under conditions involving repeated thermal cycling. The transient temperature rise during thermal cycling directly affects the stress distribution within the SOFC structure, particularly inducing non-uniform thermal stresses in the electrolyte layer. This can readily lead to cracking and fracture of the SOFCs, potentially degrading overall system performance. Therefore, investigating the effects of cyclic thermal loading on structural stress distribution is essential for optimizing SOFC design. To this end, this study developed a coupled thermo-chemo-mechanical finite element analysis for a planar tubular SOFC. The model is employed to analyze the influence of thermal impact on the thermal stress distribution within the cell structure under multiple thermal cycling conditions. The results indicate that both the transient temperature rise during SOFC operation and the number of thermal cycles significantly affect the peak stress in the electrolyte layer and the overall performance stability of the cell. By optimizing the geometric configuration of the flat-tubular and the transient temperature rise during thermal cycling, the thermal stress field distribution in the electrolyte can be improved. These findings provide theoretical guidance for optimizing the design and engineering application of high-temperature SOFCs. Full article

MoS₂ acts as a high-performance lubricant, enhancing friction material stability, reducing wear and noise under extreme conditions, and preserving friction pair performance. However, its tendency to decompose and poor matrix wettability make surface modification essential for effective use in Cu-based composites. In this study, comprehensive investigations combining macro-scale and micro-scale friction experiments were conducted to examine the interfacial friction behavior of MoS₂ with different coatings and its tribological effects on copper-based composites under varying braking energy densities. The results indicate that the nickel coating suppressed MoS₂ decomposition, forming a high-strength diffusion interface with the matrix. This enhances the frictional stability and suppresses interfacial defect formation during micro-friction tests. However, the copper coating formed a poor-strength diffusion-reacting interface with matrix, leading to unstable friction at the interface and interface failure. Coating-dependent interfacial properties and micro-friction behaviors lead to varying tribological performance in Cu-based composites with MoS₂ during macro-friction tests. Nickel-plated MoS₂ (MoS₂@Ni) exhibits superior lubrication and frictional stability. The friction coefficients of Cu-based composites with MoS₂@Ni under low, medium and high working conditions are 0.36, 0.3 and 0.24, respectively, which are 6%, 12% and 13% lower than those of copper-plated MoS₂ (MoS₂@Cu). Meanwhile, its friction stability is 0.8, 0.6 and 0.58, respectively. With rising braking energy density, wear in Cu-based composites transitions from ploughing to oxidation and then to delamination. Defective MoS₂@Cu/matrix interfaces intensify delamination wear caused by the unstable fracture of subsurface plastic deformation layer cracks at higher energy density. Full article

This study evaluates the feasibility of utilizing manufactured sand as a full or partial replacement for river sand in mass concrete production, motivated by the growing scarcity of natural river sand and stringent environmental regulations on mining. The influence of the manufactured sand replacement level, water-to-cement ratio, and fly ash content on key properties including workability, mechanical strength, early-age shrinkage, and thermal stress was systematically investigated. The results demonstrate that, while the incorporation of manufactured sand marginally impairs workability, it contributes to an improved particle size distribution of the fine aggregate. At 100% replacement, the 56-day compressive, flexural, and tensile strengths, as well as the elastic modulus of manufactured sand concrete, exceed those of river sand concrete, accompanied by a notable reduction in early-age shrinkage. A decrease in the water–binder ratio enhances mechanical performance but concurrently elevates the risk of cracking due to the increased autogenous shrinkage and adiabatic temperature rise associated with a higher cement content. The addition of an optimal amount of fly ash (e.g., 25%) effectively improves both workability and mechanical properties while substantially mitigating hydration heat, thereby reducing temperature differentials and the associated cracking risks. Microscopic analysis reveals that unhydrated particles, including fly ash and quartz, may act as initial defects within the microstructure. Overall, the replacement of river sand with manufactured sand in mass concrete is technically feasible, and an appropriate mix design optimization can achieve a desirable balance between performance and crack resistance. Full article

The precursor infiltration and pyrolysis (PIP) route is widely adopted to fabricate carbon fiber-reinforced silicon carbide (C_f/SiC) composites; however, the atomic-scale restructuring of the pyrolytic carbon/silicon carbide (PyC/SiC) interface during ceramization—and its impact on mechanical integrity—remains elusive. Here, reactive molecular dynamics (ReaxFF MD) simulations elucidate the coupled thermochemical–mechanical evolution of polycarbosilane (PCS) precursors on PyC substrates with orientation angles (OAs) of 0°, 25°, 55°, and 85°. Dynamic pyrolysis triggers a pivotal transition from sp² to sp³ hybridization at the interface. High-OA substrates (55° and 85°) present a dense population of reactive edge sites, fostering extensive cross-interfacial covalent bonding. Subsequent shear loading reveals that these pyrolysis-induced chemical bridges govern failure modes, shifting from interlayer sliding dominated by weak non-bonded interactions (0°) to ductile fracture featuring uniform plasticity and crack deflection. The OA = 55° interface attains a theoretical peak shear strength of 15 GPa and exhibits the most favorable combination of high strength and ductile failure under tensile loading, owing to an optimal balance between reactive site availability and interlayer steric openness. In contrast, the OA = 85° interface, despite comparable peak stress, fails via brittle crack penetration into the SiC matrix. By correlating atomistic structure with macroscopic performance, this study provides a bottom-up framework for engineering C_f/SiC composites via interfacial texturing and optimized pyrolysis protocols. Full article

The increasing impact of climate change and resource scarcity demands energy-efficient and resource-conserving manufacturing strategies. Metal forming offers substantial potential for lightweight construction and material efficiency. Forming-induced ductile damage, particularly void nucleation and growth, is often neglected in component design. Industrial practice still relies mainly on macroscopic mechanical properties and safety factors, while microstructural damage evolution and its influence on fatigue performance are largely disregarded. This study investigates load-path-dependent fatigue behavior and damage mechanisms using axial and combined axial–torsional fatigue tests. Particular attention is given to the phase shift d between axial and torsional loading, which strongly affects fatigue life. The results indicate that axial loading dominates damage evolution, while load path interactions significantly change fatigue performance. A phase shift of d = 90° resulted in a significant increase in the number of cycles to failure, N_f, for different total strain amplitudes with the same rotational angle amplitude of θ = 10°. These findings highlight the importance of considering load-path-sensitive stress states in fatigue assessment of formed components. Fractographic analyses, AI-assisted 3D reconstruction, and confocal laser scanning microscopy support the experimental results. Full article

Elliptical fractures are often used to characterize the deformation of real fractures; however, their deformation responses do not accurately align with those of actual fractures. Nonelliptical fractures shorten by closing near the fracture tips under compression, demonstrating significant advantages in accurately capturing fracture closure characteristics. This warrants investigation of the elastic response of rocks containing nonelliptical fractures. Focusing on single-fracture closure, this study verifies the accuracy of the numerical simulations for elliptical and nonelliptical fractures. A dynamic numerical simulation for crack deformation under compression is proposed to simulate crack closure. The stress-dependent fracture parameters are collected for models consisting of the two fracture types. Then, the pressure-dependence of wave velocities is fitted using an empirical relationship. Under initial compression (<10 MPa), the velocity increase in the elliptical fracture model is just 14.45% of that in the nonelliptical fracture model, displaying a three-stage stress-dependent behavior. The nonelliptical model follows a more realistic two-stage trend, which is more consistent with empirical observations. Moreover, the differences between microscopic parameters are negligible for the models containing elliptical and nonelliptical fractures with a small aspect ratio (≈0.003). This research lays a theoretical foundation for future inversion of fracture distributions using nonelliptical fracture models. Full article

Waste sweet potato vine fiber (WSVF) effectively extends asphalt service life by enhancing cracking resistance in gel-like base asphalt matrices, yet its crack-resistant mechanism lacks mechanical characterization. This study proposes an analytical method for evaluating WSVF-modified asphalt’s crack-resistant behavior based on the principle of mechanical energy balance. First, alkali-treated WSVF with a mass fraction of 1% was added into 70# gel-like base asphalt to prepare WSVF-modified asphalt. Lignin fiber (LF)-modified asphalt and 70# gel-like base asphalt were selected as control groups, and three types of time sweep and scanning electron microscopy tests were conducted. Then, the three-dimensional cracking volume model and damage kinetics model were established for analyzing the cracking response behavior, defining the asphalt damage variable and determining the cracking damage activation energy (E_acd). Finally, the E_acd was used to quantify the difficulty of the cracking damage process for the WSVF-modified asphalt. The reinforcement and cracking resistance mechanisms of WSVF in asphalt were analyzed by the E_acd and asphalt microstructure. The results show that the cracking volume response of WSVF-modified asphalt under cyclic loading presents three-stage nonlinear behaviors. The established fatigue damage kinetics model can accurately describe the fatigue damage evolution process of alkali-treated WSVF-modified asphalt. The E_acd values of WSVF-modified asphalt, LF-modified asphalt, and 70# gel-like base asphalt are 10.60 kJ·mol⁻¹, 21.83 kJ·mol⁻¹, and 29.74 kJ·mol⁻¹, respectively. After alkali treatment, the WSVF surface exhibits grooves, demonstrating superior adsorption and storage capacity for asphalt. The WSVF can cross link through the bonding effect of asphalt and form a three-dimensional network framework structure, which can significantly increase the E_acd and provide strengthening and toughening effects on gel-like base asphalt. In summary, E_acd values are used as a mechanical indicator to quantitatively evaluate the fatigue cracking resistance of WSVF-modified asphalt. Full article