Search Results (231)

This study systematically investigates the influence of annealing time on the microstructure and mechanical properties of a (CoCrNi)_93.5Al₃Ti₃C_0.5 medium-entropy alloy. Following hot-rolling, the alloy was subjected to annealing treatments at 900 °C for 10 min (HA900-10) and 60 min (HA900-60). Microstructural characterization revealed that both alloys contained three types of precipitates: intergranular M₂₃C₆ and MC-type carbides, as well as γ′ phase. The HA900-10 specimen exhibited a low degree of recrystallization, whereas prolonged annealing promoted partial recrystallization, leading to the formation of a slightly heterogeneous structure (HA900-60). Additionally, the extended annealing facilitated the intragranular precipitation of nanoscale γ′ phase. Room-temperature tensile tests demonstrated that the HA900-10 and HA900-60 specimens achieved yield strengths of 1276 MPa and 1202 MPa, with total elongations reaching 26% and 28%, respectively. Quantitative strengthening analysis indicated that the strength of HA900-10 primarily originated from dislocation and grain boundary strengthening. For HA900-60, an additional significant contribution arose from the dislocation shearing mechanism induced by the intragranular γ′ precipitates. Analysis of the deformation mechanisms revealed that planar slip, assisted by the formation of stacking faults, dominated the room-temperature deformation, thereby ensuring sustained work-hardening capacity. This research provides a theoretical foundation for tailoring the microstructure and properties of multi-phase medium-entropy alloys through annealing process control. Full article

This work analyzes the non-Newtonian electromagnetohydrodynamic (EMHD) flow in an irregular circular porous microchannel while incorporating the consequences of surface charge-dependent slip boundary conditions. The Jeffrey fluid is employed to examine the non-Newtonian behavior, such as elasticity. The boundary walls of the channel are considered in the form of periodic sinusoidal wave function. The mathematical formulation is developed using the momentum equation, modified Darcy’s law, the continuity equation, and Ohm’s law. The perturbation method is used to derive the solutions up to second-order approximation. The analytical expression for the velocity field and volumetric flow rate are explicitly presented. At the zeroth-order, a nonhomogeneous partial differential equation is solved, and the solutions are presented in terms of Bessel functions. The first-order problem defined by a homogeneous partial differential equation is solved using the method of separation of variables. At the second-order, a homogeneous partial differential equation is obtained, and the solution form is prescribed by the boundary conditions, consisting of a radially varying mean component and a second-harmonic angular contribution. Two- and three-dimensional plots are used to analyze and discuss the impacts of key parameters, namely the Reynolds, Darcy, and Hartmann numbers, channel corrugation amplitude and wave number, surface charge density, and the relaxation and retardation times on the velocity field and flow rate. It is found that elastic memory causes a proportional growth between the flow rate and the relaxation time, emphasizing the consequences of surface charge application in conjunction with corrugations. Conversely, maintaining a short retardation time mitigates changes in wave amplitude and surface charge. While prolonging it lessens the flow rate and diminishes corrugations and surface charge effects. The Darcy number dampens the velocity and the flow rate, while its enhancement reduces the impact of surface charge density and corrugations amplitude. For high Reynolds number, a ring phenomenon emerges which is attenuated by increased Darcy number, preventing the formation of trapped boluses close to the border. Ignoring surface charge amplifies the flow rate while its consideration diminishes the latter with reinforced impacts of surface charge and wall corrugations at higher Reynolds number. Full article

The performance of Zr-2.5Nb alloy pressure tubes in nuclear reactors is critically dependent on the behavior of precipitated hydrides. In this study, a hydrogen-charged Zr-2.5Nb alloy pressure tube was subjected to in situ tensile testing combined with electron backscatter diffraction to elucidate microcrack evolution and microstructural adaptation. Initially, longitudinal hydride–hydride interface cracks nucleated at non-coherent interfaces of two types of hydrides due to the inherent brittleness. Subsequently, stress redistribution by a small proportion of hydride–hydride interface cracks resulted in the emergence of microcracks at the transverse hydride–matrix interfaces, accompanied by partial hydride phase transformation. Finally, under high strain conditions, increased dislocation movement in the matrix triggered a single slip system, leading to the formation of numerous low-angle grain boundaries. As strain further increased, multiple slip systems were activated, and longitudinal matrix–matrix interface cracks began to nucleate at certain grain boundary locations. Full article

Alumina ceramics used in semiconductor plasma environments require high densification, microstructural homogeneity, and stable performance under increasingly aggressive processing conditions. However, systematic studies linking slurry processing parameters to the plasma resistance of alumina ceramics remain limited. In this study, the effects of slurry preparation parameters—specifically milling and aging—and sintering atmosphere on the densification, mechanical strength, and plasma etching resistance of slip-cast alumina ceramics were systematically investigated. Optimal dispersion stability was achieved under 12 h milling and 12–24 h aging conditions, resulting in homogenized green body packing and a high relative sintered density exceeding 99%. Mechanical strength and plasma resistance were strongly influenced by slurry aging and sintering atmosphere. Specimens aged for 48 h and sintered under a low oxygen partial pressure (N₂ at 1.0 L/min) exhibited the highest flexural strength and significantly improved resistance to SF₆/Ar plasma etching, with reduced etch depth and suppressed surface roughening. These results demonstrate that coordinated slurry processing and sintering atmosphere control is an effective strategy for designing high-reliability, plasma-resistant alumina ceramics for high-demand semiconductor manufacturing environments. Full article

The Yutian region at the southwestern termination of the Altyn Tagh Fault has experienced four moderate-to-strong earthquakes since 2008, providing an opportunity to investigate fault interactions within a transtensional tectonic setting. In this study, we derive the coseismic deformation and slip model of the 2020 Mw 6.3 Yutian earthquake using ascending and descending Sentinel-1 InSAR data. The deformation field exhibits a characteristic subsidence–uplift pattern consistent with normal faulting, and the preferred slip model indicates a north–south-striking fault with slip concentrated at depths of 6–9 km. To place this event in a broader tectonic context, we incorporate published slip models for the 2008 and 2014 earthquakes together with a simplified finite-fault model for the 2012 event to construct a unified four-event source framework. Static Coulomb stress calculations reveal complex interactions among the four earthquakes. Localized positive loading from the 2012 event partially counteracts the negative $\Delta CFS$ imposed by the 2008 and 2014 earthquakes, reshaping the stress field rather than simply promoting or inhibiting failure. The cumulative stress evolution shows persistent unclamping and repeated shear-stress reversals, indicating that the 2020 earthquake resulted from long-term extensional loading superimposed on multi-stage coseismic stress redistribution. These results demonstrate that multi-event stress analysis provides a more reliable framework for assessing seismic hazards in regions with complex local stress fields. Full article

Changes in preservation conditions act as an important environmental filter driving shifts in microbial communities. However, the precise identities, functional traits, and ecological mechanisms of the dominant agents driving stage-specific deterioration remain insufficiently characterized. This study investigated microbial communities and dominant fungal degraders in waterlogged versus dried bamboo slips using amplicon sequencing, multivariate statistics, and microbial isolation. Results revealed compositionally distinct communities, with dried slips sharing only a small proportion of operational taxonomic units (OTUs) with waterlogged slips, while indicating the persistence of a subset of taxa across preservation states. A key discovery was the dominance of Fonsecaea minima (92% relative abundance) at the water-solid-air interface of partially submerged slips. Scanning electron microscopy (SEM) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) indicate that this fungus forms melanin-rich, biofilm-like surface structures, suggesting enhanced surface colonization and stress resistance. In contrast, the fungal community isolated from dried slips was characterized by Apiospora saccharicola associated with detectable xylanase activity. Meanwhile, the xerophilic species Xerogeomyces pulvereus dominated (99% relative abundance) the storage box environment. Together, these results demonstrate that preservation niches select for fungi with distinct functional traits, highlighting the importance of stage-specific preservation strategies that consider functional traits rather than taxonomic identity alone. Full article

This study presents an experimental and numerical investigation into the mechanical behavior of corrugated steel–concrete composite bridge decks with composite dowel shear connectors. Four full-scale specimens were fabricated and subjected to flexural tests to obtain and analyze the load–deflection and load–strain curves. A finite element model was developed and validated against the experimental results. The validated model was subsequently applied to analyze the load-carrying process and to perform parametric sensitivity analysis. The effects of the concrete strength grade, steel strength, corrugated steel plate thickness, concrete slab thickness, and corrugated steel plate height on the ultimate bearing capacity were evaluated. The results indicate that corrugated steel–concrete composite bridge decks were subjected to concrete shear failure. The ultimate bearing capacity of the bridge deck reached approximately 3.36 times the design value, demonstrating a high safety reserve. Throughout the entire flexural failure process, the shear connectors performed effectively, with only minimal relative slip observed at the steel–concrete interface. At the instance of failure, only partial areas of the corrugated steel plate yielded. To fully exploit the structural potential, the key design parameters require rational coordination. Full article

As a commonly used dental restorative material, light-cured composite resin exhibits mechanical properties that closely match those of natural tooth structure. In the process of biting, the filling material falls off severely due to fretting between the filling material and the fixed interface of the teeth, which shortens the life of the filling material. This study aimed to investigate the mechanisms and contributing factors of this phenomenon. In particular, this study investigated the friction and wear mechanisms at the tangential fretting interface between light-cured composite resin and the tooth substrate under varying fretting amplitudes, normal loads, and lubrication conditions. In artificial saliva, the friction coefficient increased with the fretting amplitude and decreased with the increase in the normal load. The result showed that when the fretting amplitude was large or the normal load was small, the fretting was always in the complete slip regime. When the fretting amplitude was small or the normal load was large, the fretting changed from the complete slip zone to the partial slip regime. The minimum friction coefficient in milk was 0.117, and the maximum friction coefficient in artificial saliva was 0.567. Coke and milk have little effect on the fixation of filling materials. Abrasive wear was the predominant mechanism, with small amplitudes or high loads leading to adhesive wear. The composite resin exhibited the least wear in cola and milk, while soda water and artificial saliva caused significantly greater damage. Full article

Due to their superior tribological properties compared to conventional materials, the use of functionally graded materials (FGMs) has long become indispensable in mechanical engineering. The wide variety of in-depth gradings means that solving contact problems requires specific, complex numerical analysis. In many cases, however, the spatial change in Young’s modulus can be approximated by a power law, which allows closed-form analytical solutions. In the present work, integral equations for solving tangentially loaded power-law graded elastic half-planes are derived by using the Mossakovskii–Jäger procedure. In this way, the application of highly complicated singular integrals arising from a superposition of fundamental solutions is avoided. A distinction is made between different mixed boundary conditions. The easy tractability of the novel equations is substantiated by solving the plane strain fretting contact of a rigid parabolic cylinder and a power-law graded (PLG) elastic half-space. The effect of the type of in-depth grading on the dissipated energy density and the total energy lost per cycle is investigated in detail. A comparison of the total dissipated energy per cycle shows that, for very thin stiff layers on soft substrates, the total dissipated energy exceeds that of a homogeneous material. The same trend is observed for thick layers of a functionally graded material whose Young’s modulus gradually increases with depth, matching that of the underlying substrate at the bonded interface. In addition, a closed-form analytical solution for the total dissipated energy per cycle for plane strain parabolic contact of elastically homogeneous material is presented for the first time. Full article

Greenhouse gas (GHG) emissions from maritime transport account for nearly 3% of global totals, making the decarbonisation of this sector a critical priority. In response, the International Maritime Organization (IMO) adopted the GHG Strategy, targeting the full decarbonisation of international shipping by 2050, with interim milestones in 2030 and 2040. This study evaluates the greenhouse gas fuel intensity of three representative vessel types, an oil tanker, a container ship, and a bulk carrier, using one-year operational fuel consumption data in line with the Regulations of the IMO Net-Zero Framework. Both conventional fuels, including conventional marine fuels, and alternative options, encompassing liquefied natural gas (LNG), e-hydrogen, e-ammonia, e-methanol, and biodiesel, are assessed for compliance during 2028–2035. The findings reveal that conventional fuels are unable to meet future targets, resulting in significant compliance deficits and balancing costs of remedial units. LNG provides short-term benefits but is limited by methane slip. In contrast, e-hydrogen and e-ammonia enable long-term compliance and generate surplus units. E-methanol shows a partial potential, while biodiesel delivers only modest improvements. The results underscore the need for a transition toward near-zero-well-to-wake-emission fuels. This study contributes by combining life cycle assessments with regulatory compliance analysis, offering insights for policymakers and industry stakeholders. Full article

Textile-reinforced concrete (TRC) sandwich panels with lightweight cores are a promising solution for sustainable and slender building envelopes. However, their structural performance depends strongly on the shear connection between the outer shells. This study investigates the flexural behavior of TRC sandwich panels with glass fiber-reinforced polymer (GFRP) rod connectors under four-point bending. Three full-scale specimens were manufactured with high-performance concrete (HPC) face layers, an expanded polystyrene (EPS) core, and 12 mm GFRP rods as shear connectors. The panels were tested up to failure, with measurements of load–deflection behavior, crack development, and interlayer slip. Additionally, a linear-elastic finite element model was developed to complement the experimental campaign, capturing the global stiffness of the system and providing complementary insight into the internal stress distribution. The experimental results revealed stable load-bearing behavior with ductile post-cracking response. A degree of composite interaction of γ = 0.33 was obtained, indicating partially composite action. Slip measurements confirmed effective shear transfer by the GFRP connectors, while no brittle failure or connector rupture was observed. The numerical analysis confirmed the elastic response observed in the tests and highlighted the key role of the GFRP connectors in coupling the TRC shells, extending the interpretation beyond experimental results. Overall, the study demonstrates the potential of TRC sandwich panels with mechanical connectors as a safe and reliable structural solution. Full article

This paper presents a comprehensive and hybrid control framework for the real-time regulation of drillstring systems that are subject to complex nonlinear dynamics, including torsional stick–slip oscillations, coupled axial vibrations, and intricate bit–rock interactions. The model also accounts for parametric uncertainties and external disturbances typically encountered during rotary drilling operations. A robust sliding mode controller (SMC) is designed for inner-loop regulation to ensure accurate state tracking and strong disturbance rejection. This is complemented by an outer-loop model predictive control (MPC) scheme, which optimizes control trajectories over a finite horizon while balancing performance objectives such as rate of penetration (ROP) and torque smoothness, and respecting actuator and operational constraints. To address the challenges of partial observability and noise-corrupted measurements, an Ensemble Kalman Filter (EnKF) is incorporated to provide real-time estimation of both internal states and external disturbances. Simulation studies conducted under realistic operating scenarios show that the hybrid MPC–SMC framework substantially enhances drilling performance. The controller effectively suppresses stick–slip oscillations, provides smoother and more stable bit-speed behavior, and improves the consistency of ROP compared with both open-loop operation and SMC alone. The integrated architecture maintains robust performance despite uncertainties in model parameters and downhole disturbances, demonstrating strong potential for deployment in intelligent and automated drilling systems operating under dynamic and uncertain conditions. Full article

The long-term flexural performance of steel-concrete composite beams after creep is influenced by multiple factors such as the degree of shear connection, cross-sectional form, and boundary conditions. The engineering community has an ambiguous understanding of the coupling effects of these factors. To address this issue, this paper conducts systematic experimental research: six simply supported beams (three box-shaped, three I-shaped) and four continuous beams (two box-shaped, two I-shaped) were designed with three degrees of shear connection (0.57, 1.08, 1.53). These beams first underwent simulated creep tests (24 °C, 80% relative humidity, 10 kN load, 180 days), followed by monotonic bending tests. The results indicate: (1) A high degree of shear connection (1.53) reduces creep deflection by 15–20% compared to partial connection (0.57) and delays the initiation of interface slip to 30% of the ultimate load; (2) Box sections exhibit 10–15% lower creep deflection than I-sections, though both experience 40–60% stiffness reduction after creep; (3) Continuous beams show a 25% improvement in crack resistance in the negative moment region and a 50% increase in flexural capacity at mid-span compared to simply supported beams; (4) After creep, the elastic modulus of concrete decreases by 40–60% (inversely related to the degree of shear connection), with fully connected specimens retaining 55–61% of their strength, while partially connected specimens retain only 43–49%. This study quantifies the degradation patterns of concrete performance, clarifies the influence mechanisms of key structural factors, and provides theoretical and experimental support for the long-term performance design of composite beams. Shear connection design is crucial for mitigating creep effects. Full article

Plastic deformation processes are widely used in metal forming. At the same time, they produce crystallographic textures that determine a material’s anisotropy—for example, its elastic, plastic, or magnetic anisotropy. Because these properties have significant practical implications and require precise control, understanding the mechanisms of texture formation is essential. Consequently, the evolution of texture during plastic forming remains an important topic for both scientific and engineering communities. The most important models describing crystallographic texture development during plastic deformation were briefly reviewed. Based on a comparison of experimental results with numerical simulations obtained using the authors’ original fluctuating stress state (FSS) model, the main texture components were identified. It was shown that their volume fractions are primarily related to deformation fields in grains of polycrystalline material constrained by extreme boundary conditions, as well as to anisotropy in slip system hardening (A). The influence of both parameters and rolling true strain (1.5 and 2) on the copper rolling texture was evaluated by quantifying the fractions of the texture components, including the strong ones (B, S, Cu) and the weaker ones (G, W, rW). This constitutes the main novelty of the present work. Full article

Fiber-reinforced polymer (FRP)–concrete bonding is widely adopted for structural strengthening, yet its durability is highly vulnerable to freeze–thaw (FT) degradation. This study combines experimental testing with interpretable machine learning (ML) to reveal the degradation mechanism and predict the interfacial behavior of FRP–concrete systems under FT exposure. Single-lap shear tests showed that all specimens failed through interfacial debonding accompanied by partial concrete peeling. The ultimate bond strength decreased by 6.0–18.5%, and the peak shear stress dropped by 53–80%, indicating a pronounced loss of ductility and adhesion. To extend the analysis, experimental data were integrated with literature datasets, and three ensemble ML algorithms—AdaBoost, Random Forest (RF), and Extreme Gradient Boosting (XGBoost)—were employed to predict key bond–slip parameters including ultimate bond strength, local maximum bond stress, slip values, and interfacial fracture energy. Among them, XGBoost achieved the highest predictive accuracy, with R² values exceeding 0.94 for most output parameters and consistently low RMSE values. Shapley Additive exPlanations (SHAP) and Partial Dependence Plots (PDPs) further identified adhesive tensile strength, fiber modulus, FRP thickness, and concrete strength as dominant factors and defined their optimal ranges. The findings offer a scientific foundation for evaluating and predicting the long-term bond durability of FRP–concrete systems and support the development of reliable reinforcement strategies for infrastructure in cold and severe environments. Full article