Search Results (789)

Acoustic emission (AE) technology, a kind of non-destructive testing method, was used in this study to monitor the fracture process of Q245R steel in the single edge notched tension (SENT) test. The obtained AE signals were first processed by the sensor gauge method to distinguish the noise and signals related to a fracture. Based on the filtered data, it was found that the load-displacement curve and load–Crack Mouth Opening Distance (CMOD) curve of the fracture development were correlated with the characteristics of signals. In addition, an AE crack development index (CDI) was proposed to characterize different stages in the crack propagation process, and the results were verified by unloading compliance experiments. The results showed that the condition of structure can be well characterized by trends of cumulative counts and peak amplitudes of AE signals. In addition, stable cracks were found to occur when the load reached 92% of the ultimate load which produced AE signals with high counts, duration, and more high-amplitude signals. The proposed AE CDI of 40%max(CDI), 50%max(CDI), and 60%max(CDI) reflects the elastic, plastic, and stable crack propagation stages under monotonic tension, respectively, and remains stable even when the tensile loading method changes. Full article

Incorporating waste engine oil bottoms (WEOBs) as rejuvenators into reclaimed asphalt pavement offers a sustainable solution to reduce the consumption of non-renewable resources. To explore the effect of WEOBs on aged asphalt, WEOB-rejuvenated asphalt (WEOB-asphalt) with different thermal-oxidative aging times was prepared. Subsequently, viscosity, double-edge-notched tension (DENT), temperature sweep, linear amplitude sweep (LAS), and Fourier transform infrared spectroscopy (FTIR) tests were conducted to investigate the performance of WEOB-asphalt. The results indicate that WEOB-asphalt shows acceptable thermal-oxidative aging ability within 180 min. The WEOB-asphalt experiences a small decrease in critical crack tip opening displacement within a 180 min aging time. Additionally, the temperature sensitivity of WEOB-asphalt is low, and the rutting factors at temperatures of 46 °C and 52 °C can significantly distinguish the thermal-oxidative aging performance of asphalt at different aging degrees. The fatigue life of WEOB-asphalt decreases compared to the original asphalt after 540 min of aging when the strain exceeds 0.04%. Furthermore, WEOB-asphalt displays increased carbonyl and sulfoxide groups, indicating poorer thermal-oxidative aging resistance than the original asphalt. Based on these results, it is suggested that WEOB-asphalt should be used in areas with mild climate conditions to avoid its rapid secondary aging. Full article

The emulsification of a molten fusible metal alloy in a liquid epoxy matrix with its subsequent curing is a novel way to create a highly concentrated phase-change material. However, numerous challenges have arisen. The high interfacial tension between the molten metal and epoxy resin and the difference in their viscosities hinder the stretching and breaking of metal droplets during stirring. Further, the high density of metal droplets and lack of suitable surfactants lead to their rapid coalescence and sedimentation in the non-cross-linked resin. Finally, the high differences in the thermal expansion coefficients of the metal alloy and cross-linked epoxy polymer may cause cracking of the resulting phase-change material. This work overcomes the above problems by using nanosilica-induced physical gelation to thicken the epoxy medium containing Wood’s metal, stabilize their interfacial boundary, and immobilize the molten metal droplets through the creation of a gel-like network with a yield stress. In turn, the yield stress and the subsequent low-temperature curing with diethylenetriamine prevent delamination and cracking, while the transformation of the epoxy resin as a physical gel into a cross-linked polymer gel ensures form stability. The stabilization mechanism is shown to combine Pickering-like interfacial anchoring of hydrophilic silica at the metal/epoxy boundary with bulk gelation of the epoxy phase, enabling high metal loadings. As a result, epoxy shape-stable phase-change materials containing up to 80 wt% of Wood’s metal were produced. Wood’s metal forms fine dispersed droplets in epoxy medium with an average size of 2–5 µm, which can store thermal energy with an efficiency of up to 120.8 J/cm³. Wood’s metal plasticizes the epoxy matrix and decreases its glass transition temperature because of interactions with the epoxy resin and its hardener. However, the reinforcing effect of the metal particles compensates for this adverse effect, increasing Young’s modulus of the cured phase-change system up to 825 MPa. These form-stable, high-energy-density composites are promising for thermal energy storage in building envelopes, radiation-protective shielding, or industrial heat management systems where leakage-free operation and mechanical integrity are critical. Full article

Because of its strong bearing capacity and large size, a thick and hard roof is the main source of strong ground pressure in a stope, and its breaking and migration mechanism and effective control are very important for realizing safe and efficient mining in coal mines. In this paper, by constructing a numerical model that fully considers the actual occurrence conditions of such a roof, the control law of the occurrence conditions of a thick and hard roof on its fracture law and strata behavior is systematically studied, and the control mechanism of the movement and hydraulic fracturing of this kind of roof is revealed. The results show that (1) the fracture process of a thick hard roof is characterized by three stages—crack initiation, extension, and overall instability—and the “pressure arch” structure formed by the overlying huge hard rock stratum is the fundamental force source leading to strong ground pressure; (2) the roof thickness and horizon significantly control the stress distribution and fracture behavior of coal and rock mass, and the peak stress of coal and rock mass is positively correlated with the roof thickness, but negatively correlated with its horizon; (3) with the increase in roof thickness, the dominant fracture mechanism changes from tension type to tension–shear composite type, which leads to a significant increase in fracture step. Hydraulic fracturing technology can effectively cut off the “pressure arch” structure and optimize the stress field of surrounding rock. After fracturing, the first weighting step and weighting strength are reduced by 36% and 38.1%, respectively. An industrial test shows that a fracturing treatment realizes timely and orderly roof caving and achieves the controllable weakening and safe promotion of the thick and hard roof. This study provides a solid theoretical basis and a successful engineering practice model for roof disaster prevention and control under similar geological conditions. Full article

Steel plates with open holes are common in engineering structures such as bridges and towers for pipeline penetrations and connections. These openings, however, induce significant stress concentration under alternating tension–compression loading (stress ratio R = −1), drastically accelerating fatigue crack initiation and threatening structural integrity. Effective identification and mitigation of such stress concentrations is crucial for enhancing the fatigue resistance of perforated components. This study proposes a closed-loop methodology integrating theoretical weak zone identification, targeted CFRP reinforcement, and experimental validation to improve the fatigue performance of open-hole steel plates. Analytical solutions for dynamic stresses around the hole were derived using complex function theory and conformal mapping, identifying critical stress concentration angles. Experimental tests compared unreinforced and CFRP-reinforced specimens in terms of circumferential strain distribution, dynamic stress concentration behavior, and fatigue life. Results indicate that Carbon fiber-reinforced polymer (CFRP) reinforcement significantly reduces stress concentration near 90°, smooths polar strain distributions, and slows strain decay. The S–N curves shift upward, indicating extended fatigue life under identical stress amplitude and increased allowable stress at identical life cycles. Comparison with standardized design curves confirms that reinforced specimens meet higher fatigue categories, providing practical design guidance for perforated plates under alternating loads. This work establishes a systematic framework from theoretical prediction to experimental verification, offering a reliable reference for engineering applications. Full article

Membrane rupture, induced by lipid peroxidation, is a severe threat to osmotic balance, as membrane pores contribute to ferroptosis, an iron-dependent cell death. To alleviate osmotic stress, membrane constituents dynamically reconstruct the membrane and interact with intracellular molecules. Tumor-derived acidosis shift glycolysis-dependent metabolism toward lipid metabolism, increasing polyunsaturated fatty acids (PUFAs). PUFAs enhance membrane fluidity but make cancer susceptible to lipid peroxidation. Also, the ionization of phospholipids under low pH can accelerate membrane rupture. This stress can be mitigated by the redistribution of cholesterol, which maintains tension–compression balance and acts as antioxidants. When excessive reactive aldehydes—byproducts of lipid peroxidation—overwhelm cholesterol’s protective role, lipid peroxides promote membrane cracks. Moreover, a deficiency in glutathione can alter cholesterol’s function, turning it into a pro-oxidant. In contrast, ceramide, derived from membrane lipids, indirectly prevents ferroptosis by facilitating cytochrome c release. This review integrates recent findings on how membrane components and environmental stressors influence ferroptosis. It also suggests potential therapeutic strategies. This could advance our understanding of ferroptosis in cancer. Full article

This paper presents a high-fidelity numerical simulation of curvilinear fatigue crack growth (FCG) through a modified Compact Tension (CT) specimen made of Haynes 230 nickel-based superalloy. The specimen’s design, featuring three extra holes, was intentionally chosen to induce mixed-mode loading and complex, non-linear crack paths. Crucially, this configuration allows for a thorough examination of how the specimen’s geometry, restraints, or minor manufacturing discrepancies affect the localized stress state. Experimental data corresponding to three different initial crack patterns were utilized to validate the numerical model implemented within the ANSYS simulation environment. The comparison demonstrated that the present simulated crack trajectory was significantly closer to the experimental results than those obtained from earlier numerical simulations using ZFEM-TERF and FRANC3D. Furthermore, the current study critically examined the validity of Linear Elastic Fracture Mechanics (LEFM) by analyzing the evolution of the Cyclic Plastic Zone (CPZ) size for two distinct stress ratio values: R = 0.5 and R = −1. The findings confirm the full satisfaction of the Small-Scale Yielding (SSY) criterion throughout the crack growth history for the positive stress ratio (R = 0.5). Conversely, the negative stress ratio (R = −1) caused a significant violation of the SSY assumption in the later stages of propagation. This highlights how the applicability of LEFM is largely dependent on the loading regime and underscores the necessity of employing Elastic–Plastic Fracture Mechanics (EPFM) for fully reversed cycles. This research establishes a well-founded and valuable protocol for predicting Fatigue Crack Growth (FCG) in complex superalloy components. Full article

The supporting system of super-large cooling towers is crucial for the structural safety of nuclear power plants. The X-shaped reinforced concrete column has emerged as a promising solution due to its superior stability. However, the performance of the cast-in-place base joint, which is a key force-transfer component, requires thorough investigation. This study experimentally investigates the mechanical performance of the joints under ultimate vertical compressive and tensile loads. The loads represent gravity-dominated and extreme wind uplift scenarios, respectively. A comprehensive testing program monitored load–displacement responses, strain distributions, crack propagation, and failure modes. The compression specimen failed in a ductile flexural compression manner with plastic hinge formation above the column base. In contrast, the tension specimen exhibited a tension-controlled failure pattern. Crucially, the joint remained stable after column yielding in both loading scenarios. The result validates the “strong connection–weak member” design principle. The findings confirm that the proposed cast-in-place joint possesses excellent load-bearing capacity and ductility. Therefore, the study provides a reliable design basis for the supporting structures of super-large cooling towers. Full article

Crack type classification in concrete structures is essential for assessing structural integrity, yet traditional visual inspections and RA–AF parameter-based Acoustic Emission (AE) methods suffer from subjectivity and limited ability to capture temporal signal dependencies. This study proposes TemporalAE-Net, a self-attention-based machine learning framework designed to classify tensile and shear cracks while explicitly incorporating the temporal evolution of AE signals. AE data were collected from axial tension tests, shear-failure tests, and four-point bending tests on reinforced concrete beams, and a sliding-window reconstruction method was used to transform sequential AE signals into two-dimensional temporal matrices. TemporalAE-Net integrates one-dimensional convolution for local feature extraction and multi-head self-attention for global temporal correlation learning, followed by multilayer perceptron classification. The proposed model achieved an accuracy of 99.72%, outperforming both its ablated variants without convolutional or attention modules and conventional time-series architectures. Generalization tests on 12 unseen specimens yielded 100% correct classifications, and predictions for reinforced concrete beams closely matched established crack-evolution patterns, with shear cracks detected approximately 15 s prior to visual observation. These results demonstrate that TemporalAE-Net effectively captures temporal dependencies in AE signals. Moreover, it provides accurate and efficient tensile–shear crack identification, making it suitable for real-time structural health monitoring applications. Full article

The accurate prediction of crack initiation and propagation is essential for assessing the structural integrity of mechanically joined components and other complex assemblies. To overcome the limitations of existing finite element tools, a modular Python framework has been developed to automate three-dimensional crack growth simulations. The program combines geometric reconstruction, adaptive remeshing, and the numerical evaluation of fracture mechanics parameters within a single, fully automated workflow. The framework builds on open-source components and remains solver-independent, enabling straightforward integration with commercial or research finite element codes. A dedicated sequence of modules performs all required steps, from mesh separation and crack insertion to local submodeling, stress and displacement mapping, and iterative crack-front update, without manual interaction. The methodology was verified using a mini-compact tension (Mini-CT) specimen as a benchmark case. The numerical results demonstrate the accurate reproduction of stress intensity factors and energy release rates while achieving high computational efficiency through localized refinement. The developed approach provides a robust basis for crack growth simulations of geometrically complex or residual stress-affected structures. Its high degree of automation and flexibility makes it particularly suited for analyzing cracks in clinched and riveted joints, supporting the predictive design and durability assessment of joined lightweight structures. Full article

Pre-tensioned T-beams with polygonal tendons offer high load-bearing capacity and suitability for large spans, demonstrating broad application potential in bridge engineering. The cracking state of a prestressed beam is a crucial indicator for assessing its service state, while the ultimate bearing capacity is a key metric for structural safety. In this study, we designed a novel 30 m pre-tensioned T-beam with polygonal tendons and investigated its shear cracking performance and ultimate bearing capacity under a shear-span ratio of 2.5 through a full-scale test. A graded loading protocol was employed. The results indicate that during the initial loading stage, the shear cracking load of the inclined section was 1766 kN. A distinct inflection point appeared on the load–displacement curve, accompanied by a significant reduction in stiffness. Cracks initially developed at the junctions between the web and the top flange, as well as the diaphragm, and subsequently propagated towards the shear–flexural region, exhibiting typical shear–compression failure characteristics. During the secondary loading to the ultimate state, the beam demonstrated good ductility and stress redistribution capability. The ultimate shear capacity reached 3868 kN. Failure occurred by crushing of the concrete in the compression zone after the critical inclined crack penetrated the web, with the member ultimately reaching its ultimate capacity through a plastic hinge mechanism. Strain analysis revealed that the polygonal tendons effectively restrained the premature development of inclined cracks, thereby enhancing the overall shear performance and deformation capacity. This study verifies the mechanical performance of the new T-beam under a shear span-to-depth ratio of 2.5 through calculations based on different codes and finite element numerical analysis, providing experimental evidence and theoretical references for its engineering application. Full article

Understanding the deformation–failure process of sandstone is essential for energy extraction and stability assessment. Here, laboratory mechanical tests and discrete element simulations are combined to resolve how grain size controls deformation, cracking, and failure. Under uniaxial compression, fine-grained sandstone shows the highest strength (60.85–65.37 MPa) yet undergoes an abrupt brittle transition to axial splitting at a small peak axial strain of 0.41–0.42%; coarse-grained sandstone exhibits lower strength (26.94–28.67 MPa) but fails at peak axial strains of 0.44–0.53%, on average about 17% higher than those of FGS, indicating enhanced ductility; medium-grained sandstone lies in between in both strength (41.15–43.79 MPa) and peak axial strain (0.42–0.45%). With confining pressure, fine- and medium-grained sandstones display pronounced process evolution toward ductility, whereas coarse-grained sandstone shows limited pressure sensitivity. DEM results link microcrack evolution with the macroscopic response: under uniaxial loading, fine-grained sandstone is dominated by intergranular tensile cracking, while coarse-grained sandstone includes more intragranular cracks. Increasing confinement controls the cracking process, shifting fine- and medium-grained rocks from intergranular tension to mixed intragranular tension–shear, thereby enhancing ductility; in contrast, coarse-grained sandstone at high confinement localizes shear bands and remains relatively brittle. Normalized microcrack aperture distributions and fragment identification capture a continuous damage accumulation process from micro to macro scales. These process-based insights clarify the controllability of failure modes via grain size and confinement and offer optimization-oriented guidance for design parameters that mitigate splitting and promote stable deformation in deep sandstone reservoirs and underground excavations. Full article

Bedding angles (BAs) in coal mining promote shear failure and can trigger rockbursts. Using Particle Flow Code (PFC) direct shear simulations on coal with BA = 0°, 30°, 60°, and 90°, we quantified BA effects on mechanical behavior and cracking. Increasing BA reduces shear strength and shear modules, reaching minimum of 4 MPa and 0.7 GPa at 90°. Failure modes shift from progressive, bedding parallel shearing at 0° to mixed paths at 30–60°, and abrupt brittle failure at 90°. Crack density and orientation evolve systematically: dense bedding parallel shear at 0°; more dispersed, lower-density mixed shear tension at 30–60°; and reconcentrated, high-density cracking causing premature shear at 90°. Corresponding force chain patterns aligned at 0°, dispersed at 30–60°, and realigned at 90° govern these outcomes by modulating stress transfer across bedding interfaces. Overall, BA is the first-order control on coal shear instability; the quantified thresholds and mechanisms provide actionable guidance for excavation orientation, support design, and targeted monitoring to reduce shear out and rockburst risks in coal mines. Full article

This study investigates the influence of braiding angles on the mechanical behavior and damage mechanisms of three-dimensional (3D) braided composites under uniaxial compressive and tensile loading. By integrating uniaxial compression and tension tests with finite element (FE) analysis, the relationships between mesoscale damage initiation, propagation, and the macroscopic mechanical properties were revealed. Results demonstrate that the 3D4d-20° model exhibits higher stiffness and compressive strength but lower compressive failure strain compared to the 3D4d-40° model, attributed to differences in fiber spatial arrangement and matrix cracking propagation. Conversely, the 3D4d-40° model shows enhanced tensile performance but greater matrix-dominated damage under tension. Moreover, as the braiding angle increases, the ratio of tensile strength to compressive strength in 3D braided composites decreases accordingly. Comparative analysis of damage evolution pathways reveals that smaller braiding angles (20°) initiate damage earlier under compression, while larger angles (40°) promote transverse fiber bundle failure and matrix degradation. This research not only elucidates the underlying microscale damage mechanisms of 3D braided composites under compression loading but also highlights the differences in damage patterns between compressive and tensile loading, providing theoretical foundations for structural design and performance optimization of such composite materials. Future work will focus on incorporating interfacial effects and manufacturing-induced defects to refine the model further. Full article

Slope failures frequently occur during rainfall, earthquakes, and long-term weathering, and reinforcing bar insertion is widely used worldwide to prevent such failures. In this method, steel bars are installed in pre-drilled holes and bonded to the ground with grout, with a pressure plate resisting deformation; however, tensile forces generated during slope movement may crack the hardened grout and reduce performance. To address this issue, we propose an Early-stage Prestressed Reinforcing Bar Insertion Method, in which tensile load is applied to the bar before grout hardening. Grout is injected while maintaining tension, allowing the bar to remain prestressed after construction and inducing compressive stress in the grout, which is expected to improve resistance against tensile loading. A field construction test and numerical finite-element analysis were conducted to verify performance. The test confirmed constructability within half a day and retained tensile force of 42 kN after 30 days. The numerical model reproduced measured axial forces and indicated that the hardened grout remained in compression, with an average compressive stress of 3680 kN/m². These results demonstrate that prestressing can enhance grout tensile resistance. The method shows promise for future application and potential extension to similar anchoring systems. Full article