Search Results (33)

Brittle geomaterials such as coal and rock are prone to unstable failure under high stress and dynamic disturbances, where rapid release of stored elastic strain energy can trigger dynamic disasters. Polyurea, a high-strength and high-ductility elastomer, can form a continuous flexible coating on the surface of coal/rock to regulate their deformation–fracture behavior. Here, uniaxial compression tests were performed on coal specimens coated with polyurea layers of different thicknesses (0–1.25 mm). Acoustic emission (AE) and digital image correlation (DIC) were jointly employed to characterize macroscopic deformation, microcrack evolution, fracture-mode transition, and energy partitioning. The results show that polyurea provides passive lateral confinement that suppresses lateral expansion and shifts macroscopic failure from brittle splitting to progressive ductile damage. AE-based AF–RA analysis indicates that thicker coatings increase the normal stress and shear resistance along potential fracture planes, promoting a microfracture transition from shear-dominated to tension-dominated cracking. Energy analysis demonstrates that the coating enhances pre-peak energy dissipation via coordinated deformation with the coal, while thicker coatings (≥1.00 mm) exhibit pronounced post-peak elastic tensile deformation to absorb and buffer fracture-released energy, impeding the instantaneous energy release typical of bare coal. Moreover, the elastic energy index shows that polyurea markedly reduces impact tendency, with an appropriate thickness stabilizing specimens from strong to weak/non-impact propensity. These findings clarify the coupled confinement–fracture–energy regulation mechanisms of polyurea coatings and provide quantitative guidance for coating-thickness design to mitigate dynamic failure hazards in brittle materials. Full article

This study examines why ice covers on the Churchill River in Labrador crack during winter and how weather, river flow, freezing conditions, and riverbed features contribute to these events. Using data from 2010 to 2025 and satellite imagery, the study shows that cracks most often occur in December to February when heavy snow, rapid flow changes, or long cold periods place stress on the ice. Cracking also frequently starts near sandbars where the ice is weaker. The results highlight that no single factor causes cracking. Instead, a combination of snow load, temperature, flow variability, and local river conditions determines when and where cracks form. There is also a disconnect from flow regulation since cracks also formed in 2012 before the construction of the dam began in 2015. A field survey was also carried out employing a combination of borehole jack (BHJ) testing and ground-penetrating radar (GPR) surveys to quantify spatial variations in ice strength and thickness across a portion of the lower Churchill River across two sandbars. In situ BHJ measurements were conducted at multiple sites to determine confined compressive ice strength under both floating and grounded conditions, revealing substantial local variability linked to differences in ice support and the presence of white versus black ice. Complementary GPR transects using 500 MHz and 1000 MHz systems provided high-resolution profiles of ice thickness and internal structure, enabling identification of transitions between grounded and floating ice. The integrated BHJ–GPR approach allowed direct comparison between point-scale strength measurements and spatially continuous thickness and grounding patterns, demonstrating that grounded ice and ice containing higher proportions of white ice exhibited more complex stress states and greater variability in mechanical response. Together, these measurements highlight the importance of combining geophysical surveying with in situ mechanical testing to better understand how environmental conditions control ice integrity and potentially influence ice-jam lodgement propensity along regulated subarctic rivers. Full article

High-load sliding components, including gun barrels, are susceptible to accelerated wear and damage due to coupled thermal-mechanical stresses and reciprocating frictional conditions. Therefore, enhancing their operational lifespan requires the application of wear-resistant coatings with high melting points for effective surface protection. In this study, Ta-10W alloy coatings were deposited on CrNi3MoVA steel substrates through electricspark deposition, focusing on deposition voltage as a critical parameter. Experimental results indicate that the Ta-10W coatings are primarily composed of α-Fe, α-Ta₂O₅, δ-Ta₂O₅, α-Ta(W), and Fe-W intermetallic phases. An increase in deposition voltage facilitates enhanced melting and mass transfer, thereby promoting solid solution and oxidation strengthening, which results in improved hardness. However, higher voltages also induce defects such as porosity and microcracks. Hardness measurements and friction-wear tests demonstrate that coatings deposited at 80 V exhibit optimal performance, attaining the highest hardness (~753 HV) and a friction coefficient similar to that at 60 V. Conversely, the friction coefficient increases at 100 V due to defects and coating spalling. The wear mechanism transitions from adhesive wear at 60 V to adhesive wear with minor plastic deformation at 80 V and ultimately to spalling wear at 100 V. Finite element thermomechanical simulations reveal that increasing voltage significantly elevates the equivalent interfacial stress (600–1150 MPa), thus correlating with the propensity for microcracks to propagate into longitudinal semi-penetrating cracks at elevated voltages. This study establishes a theoretical foundation for optimizing electricspark deposition process parameters and contributes to the reliability design of Ta-W alloy coatings. Full article

Aircraft brake torque tubes are safety-critical components subject to combined torsional and thermal loading. As such, in aging aircraft, fatigue cracks frequently occur at the side walls of the grooves near the fillet transitions. This study presents a detailed analysis of the stress–strain state of the torque tube support section using a thermo-mechanically coupled finite element model (FEM) developed in ANSYS 2023 R2 Workbench. The model parameters are based on operational and design data provided by Röder Component Service Center Ltd. Unlike previous studies using idealized models, this approach integrates real-world non-destructive testing (NDT) evidence to identify critical areas with high stress concentrations. The model evaluates stress distributions under normal and emergency braking. Results show that the baseline 1 mm groove fillet exhibits pronounced stress peaks, correlating with observed crack initiation sites. Increasing the fillet radius to 3 mm reduces peak equivalent stress and improves the safety-factor distribution, significantly lowering crack-initiation propensity. These findings demonstrate that even minor local geometric refinements can enhance the structural robustness of torque-transmitting components. This FE–inspection integration framework offers a transferable method for reliability assessment and design improvement in aging aircraft fleets. Full article

Crystal dumpling wrapper production is hampered by rapid surface dehydration, severe freeze-cracking propensity, and storage-induced retrogradation. Modulation of blended starch properties through functional additives was investigated. This study systematically evaluated the impact of hydroxypropyl distarch phosphate (HPDSP), trehalose (TRE), guar gum (GG), and composite phosphates (CP) on physicochemical and structural properties of wheat–potato starch composite gel. Concurrently, the effects of additives on the cracking rate of crystal dumplings and texture of wrappers were investigated. Analysis revealed that apparent viscosity was increased by all additives except CP. Different additives significantly improved the freeze–thaw stability of the composite gel during the first three cycles. GG maintained enhanced freeze–thaw stability throughout the entire freeze–thaw cycle (dehydration shrinkage rate: 2.69–40.55%). Multivariate analytical techniques (SEM, FTIR, XRD, DSC) collectively indicated that the additives effectively inhibited starch retrogradation, whilst HPDSP showed the strongest retrogradation inhibition. CP enhanced water-retention capacity and produced a softer blended gel (hardness at 21 days was 100.56 gf). Furthermore, additives significantly reduced the freezing cracking rate of crystal dumplings and improved the textural properties of dumpling wrappers. Full article

With regard to space telescopes, the processing of large optical mirrors has always been a highlight in the field of optical processing. These mirrors are typically made of hard and brittle materials such as quartz glass, microcrystalline glass, and silicon carbide. These materials have long been considered challenging to work with due to their processing efficiency and propensity for damage. This study proposes a trochoid model considering the actual motion trajectory of the cup wheel with discrete consolidated abrasive grains. Through the establishment of a process parameter–mathematical model to establish the multi-grain coupled motion trajectory, the uniformity of the trajectory is optimized to increase the material removal rate and reduce the surface damage caused by abrasive interference. The results show that the process parameter optimization using this model can effectively reduce the surface roughness of quartz glass grinding. The surface and sub-surface damage caused by grinding stress are significantly reduced, and the edge fracture area of quartz glass is decreased. The large contact area at the end face of the cup-grinding wheel enables a larger grinding depth while ensuring that cracks do not extend to the sub-surface, improving the overall surface integrity of the mirror. Full article

In hydraulic structures such as water control projects, spillway tunnels, and overflow dams that are subjected to high-velocity flow erosion, Concrete is required to exhibit high resistance to abrasion and cracking. While low water-to-binder ratio concrete can meet strength requirements, its inherent high shrinkage propensity often leads to cracking, seriously compromising long-term safety and durability under severe operating conditions. To address this engineering challenge, this study focuses on optimizing concrete performance through the synergistic combination of slag (GGBS) and silica fume (SF). This study systematically investigated the effects of incorporating GGBS (20–24%) and SF (6–10%) in a low water-to-binder ratio system with a fixed 70% cement content on key concrete properties. The evaluation was conducted through comprehensive tests including compressive strength, drying shrinkage, autogenous shrinkage, and hydration heat analysis. The results demonstrate that the blended system successfully achieves a synergistic improvement in both “high strength” and “low cracking risk.” Specifically, the incorporation of silica fume significantly enhances the compressive strength at all ages, providing a solid mechanical foundation for resisting high-velocity flow erosion. More importantly, compared to the pure cement system, the blended system not only delays the onset but also reduces the rate of early-age shrinkage, and lowers its ultimate autogenous shrinkage value. This characteristic is crucial for controlling the combined effects of thermal and shrinkage stresses from the source and preventing early-age cracking. Simultaneously, hydration heat analysis reveals that the blended system retards the heat release process, which helps mitigate the risk of thermal cracking. This study elucidates the regulatory mechanism of the GGBS-SF combination and provides a critical mix design basis and theoretical support for producing high-strength, high-abrasion-resistant, and low-shrinkage concrete in high-velocity flow environments, offering direct practical implications for engineering applications. Full article

Concrete structure integrity is significantly compromised by the primary problem of cracking. Typically, surface cracking (predominantly shrinkage-induced and thermal microcracking) is rectified using costly and time-consuming repair methods involving mortar and other techniques. Research efforts have recently shifted towards developing smart materials to reduce concrete’s propensity for cracking, enhance its structural stability, and prevent damage to its framework. Concrete designs with self-healing capabilities can safeguard against degradation and enhance long-term durability. Despite extensive research, a consensus on the optimal preparation and mechanical properties of self-healing concrete has yet to be reached. Within self-healing concrete that utilizes microcapsules, repair agents are dispersed throughout the matrix to form a bond and seal cracks as damage develops. From the viewpoint of a sustainable society, this approach appears to promote the use of construction materials. This study examined the impact of Dawson/urea–formaldehyde microcapsule-based self-healing concrete using strength tests, where the effectiveness of different microcapsule quantities (0.5–2% microcapsule by weight of cement) was assessed. Following the data and data analysis, it becomes evident that among all samples, the 1% microcapsule sample yields outstanding results for both 7-day and 28-day compressive strength. Full article

Laser additive manufacturing offers significant advantages for fabricating and repairing complex components. However, the complex solidification and remelting processes in nickel-based superalloys for additive manufacturing can introduce defects such as voids and cracks. Therefore, process parameters are crucial, as they significantly impact solidification and remelting, thereby affecting defect formation. In this study, laser-directed energy deposition was employed to evaluate the effects of our key process parameters on the formation of voids and cracks in a novel superalloy. The findings reveal that laser power and linear energy density significantly influence the void content and crack density. However, the influence of other process parameters on defect formation is relatively minimal. The optimal parameter space is characterized by a laser power range of 600~700 W, a linear energy density range of 60~90 J/mm and a powder feeding rate of 0.7~0.8 rpm. Moreover, the precipitation of fine MC-type carbides near the dendrites and grain-boundary misorientations within the range of 31~42° are associated with a higher propensity for crack formation. These insights provide a valuable reference for controlling the process parameters and understanding the cracking mechanisms in laser additive manufacturing of superalloys. Full article

This research examines the mechanical properties of fiber-reinforced modified high-water content materials intended for mining backfill applications. Conventional high-water content materials encounter several challenges, including brittleness, inadequate crack resistance, and insufficient later-stage strength. Basalt fiber (BF) and polypropylene fiber (PP) were integrated into the material system to establish a reinforcing network through interfacial bonding and bridging mechanisms to mitigate these issues. A total of nine specimen groups were developed to assess the influence of fiber type (BF/PP), fiber content (ranging from 0.5% to 2.0%), and water cement ratio (from 1.25 to 1.75) on compressive, tensile, and shear strengths. The findings indicated that basalt fiber exhibited superior performance compared to polypropylene fiber, with a 1% BF admixture yielding the highest compressive strength of 5.08 MPa and notable tensile enhancement attributed to effective pore-filling and three-dimensional reinforcement. Conversely, higher ratios (e.g., 1.75) resulted in diminished strength due to increased porosity, while a ratio of 1.25 effectively balanced matrix integrity and fiber reinforcement. Improvements in shear strength were less significant, as excessive fiber content disrupted interfacial friction, leading to a propensity for brittle failure. In conclusion, basalt fiber-modified high water content materials (with a 1% admixture and a ratio of 1.25) demonstrate enhanced ductility and mechanical performance, rendering them suitable for mining backfill applications. Future investigations should focus on optimizing the fiber matrix interface, exploring hybrid fiber systems, and conducting field-scale validations to promote sustainable mining practices. Full article

Condensate oil, due to its inherent physical and chemical properties, can accelerate the spontaneous combustion of corrosion products in storage tanks during transportation or storage, posing significant risks to the safety and sustainability of energy infrastructure. While prior research has primarily examined crude oil or reactive sulfur effects on tank corrosion, the mechanistic role of condensate oil in promoting corrosion product ignition remains unclear. To address this knowledge gap, this study investigates the impact of condensate oil on simulated tank corrosion product compounds (STCPCs) through a combination of microstructural analysis (XRD and SEM) and thermal behavior characterization (TG-DSC). The results reveal that condensate oil treatment markedly increases STCPC surface roughness, inducing crack formation and pore proliferation. These structural changes may enhance the adsorption of O₂ and condensate oil, thereby amplifying STCPC reactivity. Notably, condensate oil reduces the thermal stability of STCPC, increasing its spontaneous combustion propensity. DSC analysis further demonstrates that condensate oil introduces additional exothermic peaks during oxidative heating, releasing heat that accelerates STCPC ignition. Moreover, condensate oil lowers the apparent activation energy of STCPC by 1.44 kJ/mol and alters the dominant reaction mechanism. These insights advance the understanding of corrosion-induced spontaneous combustion and highlight critical sustainability challenges in petrochemical storage and transportation. By elucidating the hazards associated with condensate oil, this study provides actionable theoretical guidance for improving the safety and environmental sustainability of energy logistics. Future work should explore mitigation strategies, such as corrosion-resistant materials or optimized storage conditions, to align industrial practices with sustainable development goals. Full article

The residue conversion processes, coking, visbreaking, and fluid catalytic cracking (FCC), have demonstrated that feedstock quality is the single factor that most affects process performance. While, for the FCC, it is known that the heavy oil conversion at a maximum gasoline yield point can vary between 50 and 85 wt. %, for the vacuum residue hydrocracking, no reports have appeared yet to reveal the dependence of conversion on the quality of vacuum residue being hydrocracked. In order to search for such a dependence, eight vacuum residues derived from medium, heavy, and extra heavy crude oils have been hydrocracked in a laboratory unit at different reaction temperatures. The current study has witnessed that the vacuum residue hydrocracking obeys the same rule as that of the other residue conversion processes, confirming that the feedstock quality has a great influence on the process performance. A conversion variation between 45 and 85 wt. % can be observed when the sediment content in the hydrocracked atmospheric residue is within the acceptable limit, guaranteeing the planned cycle length. An intercriteria analysis was performed, and it revealed that the vacuum residue conversion has negative consonances with the contents of nitrogen and metals. Correlations were developed which predict the conversion at constant operating conditions within the uncertainty of conversion measurement of 1.7 wt. % and correlation coefficient of 0.964. The conversion at constant hydrocracked atmospheric residue (HCAR) sediment content was predicted with a correlation coefficient of 0.985. The correlations developed in this work disclosed that the higher the contents of metals, nitrogen, and asphaltenes, and the lower the content of sulfur, the lower the conversion in the hydrocracking process is. It was also shown that vacuum residues, which have the same reactivity (the same conversion at identical operating conditions), can indicate significant difference in the conversion at the same HCAR sediment content due to their diverse propensity to form sediments in the process of hydrocracking. Full article

In order to investigate the mechanical behavior of a novel pre-tensioned polygonal prestressed T-beam subject to combined bending, shear, and torsion, this study meticulously designed and fabricated a full-scale specimen with a calculated span of 28.28 m, a beam height of 1.8 m, and a top flange width of 1.75 m. A systematic static loading test was conducted. A multi-source data acquisition methodology was employed throughout the experiment. A variety of embedded and external sensors were strategically arranged, in conjunction with non-contact digital image correlation (VIC-3D) technology, to thoroughly monitor and analyze key mechanical performance indicators, including deformation capacity, strain distribution characteristics, cracking resistance, and crack propagation behavior. This study provides valuable insights into the damage evolution process of novel polygonal pre-tensioned T-beams under complex loading conditions. The experimental results indicate that the loading process of the specimen when subjected to combined bending, shear, and torsion, can be divided into two distinct stages: the elastic stage and the crack development stage. Cracks initially manifested at the junction of the upper flange and web at the extremities of the beam and at the bottom flange of the loaded segment. Subsequently, numerous diagonal and flexural–shear cracks developed within the web, while diagonal cracks also commenced to form on the top surface, exhibiting a propensity to propagate toward the support section. Following the appearance of diagonal cracks in the web concrete, both stirrup strain and concrete strain demonstrated abrupt changes. The peak strain observed within the upper stirrups was markedly greater than that measured in the middle and lower regions. On the front elevation of the web, the principal strain peak was concentrated near the connection line between the loading bottom and the upper support. In contrast, on the back elevation of the web, the principal tensile strain was more pronounced near the connection line between the loading top and the lower support. Full article

This study aims to explore the effect of microstructural parameters on the notch fatigue damage behavior of the TC21 alloy. Different levels of lamellar microstructures were achieved through distinct aging temperatures of 550 °C, 600 °C, and 650 °C. The findings reveal that increasing aging temperature primarily contributes to the augmentation of α colony (α_c) thickness, grain boundaries α phase (GBα) thickness, and α fine (α_fine) size alongside a reduction in α lath (α_lath) thickness and α_fine content. The notch alters stress distribution and relaxation effects at the root, enhancing notched tensile strength while weakening plasticity. Moreover, the increased thickness of GBα emerges as a critical factor leading to the increase area of intergranular cleavage fracture. It is noteworthy that more thickness α_lath and smaller α_fine facilitate deformation coordination and enhance dislocation accumulation at the interface, leading to a higher propensity for micro-voids and micro-cracks to propagate along the interface. Conversely, at elevated aging temperatures, thinner α_lath and larger α_fine are more susceptible to fracture, resulting in the liberation of dislocations at the interface. The reduction in α_lath thickness is crucial for triggering the initiation of multi-system dislocations at the interface, which promotes the development of persistent slip bands (PSBs) and dislocation nets within α_lath. This phenomenon induces inhomogeneous plastic deformation and localized hardening, fostering the formation of micro-voids and micro-cracks. Full article

The very high cycle fatigue (VHCF) strength of welded joints made of high-strength structural materials is generally poor, which poses a serious threat to the long life and reliability of the structural components. This work employs an ultrasonic vibration fatigue testing system to investigate the biaxial fatigue failure mechanism of the welded joints. The results revealed that under uniaxial loading conditions, the propensity for fatigue failure in plate specimens was predominantly observed at the specimen surface. Regardless of whether under uniaxial or biaxial loading, the initiation of fatigue cracks in cruciform joints was consistently traced back to unfused flaws, which were primarily located at the interface between the solder and the base material. Concurrently, it was noted that the fatigue strength of cruciform joints under biaxial loading was merely 44.4% of that under uniaxial loading. The geometric peculiarities of the unfused defects led to severe stress concentrations, which significantly reduced the fatigue life of the material under biaxial loading conditions. Full article