Search Results (6,245)

This study investigates how laser power–scan speed combinations influence densification, surface quality, and mechanical performance of Ti-6Al-4V parts fabricated by Powder Bed Fusion–Laser Beam/Metal (PBF-LB/M) on a DMG MORI LASERTEC 30 SLM (2nd generation) system. A parametric matrix was explored by varying laser power (150–400 W) and scan speed (0.9–1.4 m·s⁻¹) at constant layer thickness and hatch spacing, deliberately omitting contour exposure to isolate core scan effects. A stable processing window was identified (250–300 W; 0.9–1.0 m·s⁻¹) corresponding to ~50–60 J·mm⁻³ volumetric energy density (VED) achieved at 99.5% with residual porosity of 0.1–0.3%. In this regime, as-built roughness measured Ra = 4–6 µm on top surfaces and Ra = 15–17 µm on side surfaces. Mechanical testing in the as-built showed ultimate tensile strength (UTS) = 1150–1180 MPa and offset yield strength (YS_0.2) = 955–994 MPa, with elongation up to 6.7%. Hardness increased from 220 HV to 360 HV as densification improved. Notably, similar VED values derived from distinct power–speed combinations resulted in divergent outcomes, confirming that VED alone does not uniquely predict quality. Comparative benchmarks from the literature data highlight the performance achieved. The resulting process–property map provides a practical reference for parameter optimization, reproducibility evaluation, and transferability across platforms. Full article

Achieving thickness uniformity is a critical challenge in superplastic forming (SPF) of hemispherical shells, as standard constant-thickness blanks suffer from excessive thinning at the pole. While the literature suggests using variable thickness blanks to mitigate this issue, existing solutions often rely on complex, non-linear profiles that are expensive and difficult to manufacture. This work proposes a cost-effective, truncated conical blank design (linearly variable thickness) to optimize material distribution. The approach combines Finite Element Method (FEM) analysis and experimental validation on AZ31 magnesium alloy. The study demonstrates that the optimized truncated conical profile (α = 0.2) yields superior structural quality, drastically reducing the thinning factor to 9%. This represents a significant improvement compared to the ~14% thinning observed with conical profile (α = 0) blanks and outperforms constant-thickness blanks (30%). These results demonstrate that a simplified, easily machinable blank geometry can effectively address the thinning problem, providing a practical solution for industrial SPF applications. Full article

To mitigate the potential adverse effects of magnetic flux leakage from permanent-magnet sliding bearings on human health and the environment, this study proposes a leakage-suppressed design based on a multi-layer yoke configuration. The magnetic performance of the bearing was systematically investigated using finite element method (FEM) simulations. The results demonstrate a pronounced reduction in magnetic leakage when replacing a conventional single-layer yoke with an optimized multi-layer yoke structure. Targeted design refinements, including optimization of both the number and angular span of magnetic rings, as well as tuning of the yoke thickness, further enhance the effectiveness of the leakage-suppression strategy. The proposed multi-layer yoke configuration preserves both the magnetic force and the load-carrying capacity of the magnetic bearing, while concurrently providing a viable theoretical and engineering basis for the design and structural optimization of leakage-controlled permanent-magnet bearings. Full article

This study aims to enhance the corrosion property of 17-4PH martensitic stainless steel, a material commonly used in industrial applications including nuclear power components, to enhance its performance in borate buffer solutions. The study employed plasma-based low-energy nitrogen ion implantation at temperatures ranging from 350 °C to 550 °C for 4 h to modify the steel surface. Microstructural characterization via XRD and TEM revealed the formation of a nanocrystalline nitrided layer, with thickness increasing from 11 to 27 μm and surface nitrogen concentration rising from 29.7 to 33.1% as temperature increased. Correspondingly, the nanocrystalline grains coarsened from an average size of 2 nm to 15 nm. The main findings showed that all nitrided layers significantly improved general corrosion resistance in pH 8.4 borate solution compared to the unmodified steel. An optimal performance with a corrosion potential of −169.4 mV(SCE) and a passive current density of 0.5 μA/cm² was achieved at 450 °C, accompanying the development of a denser passive film with high polarization resistance and lower defect density. It is concluded that the high interstitial nitrogen concentration within the nanocrystalline γ′_N accelerates passivation kinetics and enhances corrosion resistance, with the applied point defect model clarifying the underlying improvement mechanism. Full article

This study developed a heat transfer model and systematically simulated heat conduction behavior during flame disinfection to optimize surface flame disinfection (SFD) technology targeting Bradysia odoriphaga larvae. By determining pest mortality rates at various temperatures, we identified 40 °C as the critical threshold. When temperature increased from 30 °C to 65 °C, the time required to achieve 50% (LT50, median lethal time, represents the baseline threshold for control efficacy) mortality dropped sharply from 131 s to merely 6 s, while the time to reach 95% mortality (LT95, i.e., 95% lethal time, represents the standard for complete control in the field) decreased from 279 s to 12 s. The model demonstrated that higher surface temperatures enabled heat to penetrate deeper into the soil. For every 20 °C increase in temperature, lethal depth increased by 2.1 cm, and heat conduction depth increased by 1.2 cm. Soil thickness exhibited a dual effect; although deeper soil could increase lethal depth, it also created thermal resistance that slowed heat penetration. In practical applications, heating a 20 cm thick soil layer to 163 °C could achieve effective pest control at a depth of 32.5 cm. This framework provides support for achieving precise flame disinfection and promotes sustainable pest management with reduced chemical pesticide use. Full article

This study aims to optimize the physical, mechanical, and thermal properties of 100% Ground Granulated Blast Furnace Slag (GGBFS) based geopolymer wood-composite panels. Pine fibers were utilized as the primary reinforcement matrix, while glass and hemp fibers were introduced as secondary reinforcements at varying proportions (3%, 6%, 9% by weight). The research investigated the effects of fiber pretreatments (hot water vs. 1% NaOH) and reinforcement hybridization. Results indicate that GGBFS successfully geopolymerized, forming a hybrid N-A-S-H and C-A-S-H gel network. Quantitative analysis revealed that 9% glass fiber reinforcement yielded the highest mechanical performance, achieving a Modulus of Rupture (MOR) of 10.05 N/mm² and Internal Bond (IB) strength of 1.32 N/mm², alongside superior water resistance (1.0% Thickness Swelling). Conversely, while hemp fiber inclusion reduced mechanical strength (MOR: 5.77 N/mm² at 9%), it significantly enhanced thermal insulation, reducing thermal conductivity to 0.10 W/m·K. It was observed that aggressive NaOH pretreatment caused alkali-induced degradation of pine fibers, negatively impacting the composite’s integrity compared to hot water treatment. This study demonstrates the feasibility of tailoring 100% slag-based geopolymer composites for either structural (glass-reinforced) or insulating (hemp-reinforced) applications using industrial by-products. Full article

Transparent conductive SnO₂ films, promising for application in electronic engineering, were obtained by sol–gel synthesis via mixing SnCl₂∙2H₂O and NH₄F solutions, followed by deposition onto glass substrates by centrifugation and heat treatment at 450 °C. The physicochemical processes of SnO₂ crystallization in water–alcohol solutions of SnCl₂ were analyzed depending on the concentration of the crystallization initiator NH₄F and the alcohols used. The sol–gel processing of the thin films was investigated using a Latin square approach. Three factors affecting the film formation conditions were varied at three levels to determine the best combination of film properties involving the maximum transparency and lowest specific electrical resistance. The effect of solvent type (ethanol, 1-butanol and isopropanol), the amount of introduced fluorine (5, 10, and 15 at. %) and the number of deposited layers (10, 15, and 20) on the composition, morphology, crystallization features, transparency and specific surface resistance of the synthesized thin films was studied. The obtained films of ~200–340 nm thickness exhibited ~78%–95% transparency in the visible spectrum range and specific surface resistance (ρ_s) from ~10⁹ to >10¹² Ω/sq. The optimal combination of thin (~250 μm) SnO₂<Sn> film target performances including transparency 84% and specific surface resistance ~10⁹ Ω/sq. was achieved in the case of their preparation in isopropanol with an average concentration of NH₄F (10 at. % F) and spin-on deposition of 20 layers. Full article

This paper presents a simulation of the heat exchange process in a solar dryer designed for corn cobs placed in flexible bulk containers (Big-Bag type). The distinctive feature of this drying system is the use of soft load-bearing containers, which simplify loading, unloading, and transportation, while also reducing mechanical damage to the corn cobs. The bottom of each container is perforated to allow the free flow of heated drying agent into the chamber. The study aims to improve the efficiency of the solar drying process to reduce the moisture content of corn cobs below 15%, thereby ensuring the required quality during storage and transport. To validate the drying regimes and parameters, heat and mass transfer processes were simulated using numerical modeling and experimental design methods based on a laboratory-scale physical model of the drying chamber. Numerical simulations were performed using the Reynolds-averaged equations coupled with the heat conduction equation for three porosity coefficients: 0.35, 0.45, and 0.55. The models provided contours of temperature and humidity distribution within the confined boundaries of the drying chamber and individual corn cobs, positioned both vertically and horizontally within the airflow zone, for varying drying durations. The core novelty of this research is the development of an optimized framework for solar drying corn in flexible containers, which integrates numerical simulation with experimental validation to establish key efficient parameters. Specifically, the study provides the following: (1) a validated regression model linking moisture content to airflow rate, drying time, and layer thickness at 45 °C; and (2) a detailed analysis of thermo-hydraulic contours within both the chamber and individual cobs for different porosities, offering practical insights for system design and operation. Full article

To address the issues of excessive sheet metal thinning and geometric deviation in single point incremental forming (SPIF), this paper proposed a bi-objective process parameter optimization framework for Al1060 sheet based on a multilayer perceptron (MLP) surrogate model and an improved multi-objective grey wolf optimization (IMOGWO) algorithm. Finite element simulations based on ABAQUS were conducted to generate a dataset considering variations in tool radius, initial sheet thickness, tool path strategy, step depth and forming angle. The trained MLP was used as the objective function in the optimization process to enable the rapid prediction of forming quality. The IMOGWO algorithm, enhanced by the Spm chaotic mapping initialization, an improved convergence coefficient updating mechanism and associative learning mechanism, was then employed to efficiently search for Pareto optimal solutions. For a truncated conical component case, optimal parameter sets were selected from the Pareto front via the entropy-weighted TOPSIS method for order preference by similarity to an ideal solution. Experimental verification showed close agreement with the simulated results, with relative errors of only 0.58% for the thinning rate and 3.10% for the geometric deviation. This validation demonstrates the feasibility and potential of the proposed method and its practical potential for improving the quality of SPIF forming. Full article

Curved sensors hold significant positions in various fields of modern science and technology, such as medical care, soft robotics, and electronic devices. Meanwhile, flexible electronic devices with film/polydimethylsiloxane substrate structures have been widely applied in the configuration design and performance enhancement of sensors. It is essential to consider the dynamic buckling behavior of film/substrate structures under bending conditions for the optimization of sensor functions. In this study, the dynamic behaviors of thin film/substrate structures with finite thickness in the curved state are investigated. Firstly, the dynamic equations considering damping and external excitation are established based on the principle of minimum energy and the Lagrange function. Secondly, the dynamic responses under different parameters are analyzed. Finally, the effects of the frequency of external excitation, pre-strain, the amplitude of external excitation strain, and the Young’s modulus and thickness of the substrate on the critical value of chaos occurrence are discussed respectively. This study is aimed at providing novel insights for the design of curved sensors based on thin film/substrate structures. Full article

Flood simulation in small- and medium-sized catchments is hindered by data scarcity and strong hydroclimatic heterogeneity. Distributed models with pedotransfer functions offer new opportunities, yet their parameter sensitivity and regional applicability remain insufficiently understood. In this study, the wflow_sbm model was applied to two catchments: the humid Tunxi basin and the semi-humid Chenhe basin, China. Model seamless parameters, defined as spatially continuous fields derived directly from global datasets using pedotransfer functions without local calibration, were generated using the HydroMT system. The parameter sensitivity, applicability of pedotransfer function derived parameters, and model performance were systematically evaluated and benchmarked against the well-established Xin’anjiang (XAJ) model, which is a conceptual lumped hydrological model widely used for flood simulation in humid and semi-humid regions of China. Sensitivity analysis identified KsatHorFrac and InfiltCapSoil as dominant in Tunxi, and KsatHorFrac and SoilThickness in Chenhe. SoilThickness derived by HydroMT underestimated flood volumes in the Chenhe basin but was substantially improved after applying a uniform scaling factor of 0.1, resulting in an effective SoilThickness of approximately 0.2 m. The wflow_sbm model achieved performance comparable to the XAJ model. Optimal calibration achieved N_SE = 0.85 in Tunxi with good performance at internal sub-catchments (Yuetan and Chengcun, N_SE > 0.70), and generally above 0.7 in Chenhe. These findings highlight the region-dependent validity of parameterization and provide guidance for distributed flood modeling in data-scarce basins. Full article

This study systematically investigates the microstructure evolution, mechanical properties, and residual stress distribution in diffusion-bonded joints between Al₂O₃ ceramic and TC4 alloy. Motivated by the need for reliable high-temperature joints in advanced applications, this work addresses the challenges posed by the materials’ physicochemical differences. Joints were fabricated at temperatures ranging from 800 °C to 950 °C under a pressure of 3 MPa for 2 h. Microstructural characterization revealed the formation of a multi-layered interfacial structure, dominated by a Ti₃Al reaction layer, whose thickness increased with bonding temperature. The highest shear strength of 54 MPa was achieved at 850 °C, representing a key quantitative outcome of this parameter optimization. Beyond this temperature, excessive growth of the brittle Ti₃Al layer and associated residual stresses led to strength degradation and interfacial cracking. A three-dimensional finite element model was developed to simulate residual stress distributions, highlighting significant tensile stresses within the Ti₃Al layer and compressive stresses in the Al₂O₃ near the interface. The model further identified critical tensile stress concentrations along the vertical edges of the ceramic, which contribute to failure during shear testing. Full article

Maritime nations around the world proactively engage in preparedness, response, and recovery activities related to marine oil spills. In addition to an individual nation’s capabilities, there are a number of response organizations that are actively engaged in the surveillance, monitoring, and remote sensing of spilled oil. A global survey was conducted of these organizations to better understand surveillance/remote sensing capabilities operationally employed today from four aerial platforms: satellites, fixed-wing aircraft, helicopters, and remotely piloted aircraft systems (RPASs). Satellite remote sensing continues to be used for both routine surveillance of coastal environments and in support of response to oil spills. Additionally, there is a strong continued use of fixed-wing aircraft, and in some cases helicopters, particularly to support operational response to oil spills. Many of these fixed-wing aircraft are outfitted with sensor suites optimized for oil spill detection and documentation. Of particular interest is the recent introduction and widespread use of RPASs for the response of marine oil spills and oiled shorelines. Respondents identified operational gaps in remote sensing capabilities to support oil spill response, including the accurate measurement of oil spill thickness and volume, differentiation between petroleum oil and biogenic materials, and the detection of water-in-oil emulsions. Survey respondents also shared remote sensing capabilities used for oiled shorelines, as well as identifying research and operational gaps in the surveillance of oil spills. Full article

Unlike classical multi-layered micro-perforated panels (MPPs), which rely on sub-millimeter orifices for sound dissipation, we propose a multi-layered porous Helmholtz resonators absorber. It consists of alternately layered perforated porous material panels and perforated rigid panels with millimeter- to centimeter-scale orifices, primarily relying on porous materials for sound energy dissipation. Theoretically, perforated porous material panels are modeled as homogeneous fluid layers using double porosity theory, and the total surface impedance is derived through bottom-to-top impedance translation. A double-layered prototype was tested to validate the theoretical and numerical models, achieving near-perfect absorption peaks at 262 Hz and 774 Hz, with a subwavelength total thickness of 11 cm and a broadband absorption above an absorption coefficient of 0.7 from 202 Hz to 1076 Hz. Simulations of sound pressure, particle velocity, power dissipation, and sound intensity flow confirm that Helmholtz resonances in each layer enhance sound entry into resistive porous materials, causing absorption peaks. Parameter studies show this absorber maintains high absorption peaks across wide ranges of orifice diameters and panel thicknesses. Finally, an optimized triple-layer porous Helmholtz resonators absorber achieves an ultra-broadband absorption above a coefficient of 0.95 from 280 Hz to 1349 Hz with only 16.5 mm thickness. Compared with conventional MPPs, this design features significantly larger orifices that are easier to fabricate and less susceptible to blockage in harsh environments, offering an alternative solution for low-frequency and broadband sound absorption. Full article

The micro-geometry of the cutting edge plays a crucial role in material flow ahead of the cutting edge and chip formation, primarily influencing chip formation mechanisms and the minimum cutting thickness. In the context of turning 304 stainless steel, however, existing research still lacks a unified quantitative framework linking “cutting edge micro-geometry—material separation behavior (separation point/minimum uncut chip thickness)—microstructural evolution of the machined surface.” This gap hampers mechanistic optimization design aimed at enhancing machining quality. This study examines the turning of 304 stainless steel by integrating analytical modeling, finite element simulation, and experimental validation to develop a predictive model for minimum cutting thickness. It analyzes the effects of tool nose radius and asymmetric edge morphology, and a microstructure evolution prediction subroutine is developed based on dislocation density theory. The results indicate that the minimum cutting thickness exhibits a positive correlation with the tool nose radius, and their ratio remains stable within the range of 0.25 to 0.30. Under asymmetric edge conditions, the minimum cutting thickness initially increases and then decreases as the K-factor varies. The developed subroutine, based on the dislocation density model, enables accurate prediction of dislocation density, grain size, and microhardness in the machined surface layer. Among the factors considered, the tool nose radius demonstrates the most pronounced influence on microstructure evolution. This research provides theoretical support and a technical reference for optimizing cutting-edge design and enhancing the machining quality of 304 stainless steel. Full article