Search Results (121)

Modern aerospace engineering places increasing emphasis on materials that combine low weight with high mechanical performance. Fiber metal laminates (FMLs), which merge metal layers with fiber-reinforced composites, meet this demand by delivering improved fatigue resistance, impact tolerance, and environmental durability, often surpassing the performance of their constituents in demanding applications. Despite these advantages, inspecting such thin, layered structures remains a significant challenge, particularly when they are difficult or impossible to access. As with any new invention, they always come with challenges. This study examines the effectiveness of the fundamental anti-symmetric Lamb wave mode (A0) in detecting weak interfacial defects within Carall laminates, a type of hybrid fiber metal laminate (FML). Delamination detectability is analyzed in terms of strong wave dispersion observed downstream of the delaminated sublayer, within a region characterized by acoustic distortion. A three-dimensional finite element (FE) model is developed to simulate mode trapping and full-wavefield local displacement. The approach is validated by reproducing experimental results reported in prior studies, including the author’s own work. Results demonstrate that the A0 mode is sensitive to delamination; however, its lateral resolution depends on local position, ply orientation, and dispersion characteristics. Accurately resolving the depth and extent of delamination remains challenging due to the redistribution of peak amplitude in the frequency domain, likely caused by interference effects in the acoustically sensitive delaminated zone. Additionally, angular scattering analysis reveals a complex wave behavior, with most of the energy concentrated along the centerline, despite transmission losses at the metal-composite interfaces in the Carall laminate. The wave interaction with the leading and trailing edges of the delaminations is strongly influenced by the complex wave interference phenomenon and acoustic mismatched regions, leading to an increase in dispersion at the sublayers. Analytical dispersion calculations clarify how wave behavior influences the detectability and resolution of delaminations, though this resolution is constrained, being most effective for weak interfaces located closer to the surface. This study offers critical insights into how the fundamental anti-symmetric Lamb wave mode (A0) interacts with delaminations in highly attenuative, multilayered environments. It also highlights the challenges in resolving the spatial extent of damage in the long-wavelength limit. The findings support the practical application of A0 Lamb waves for structural health assessment of hybrid composites, enabling defect detection at inaccessible depths. Full article

Laser cladding, a cutting-edge surface modification technique for metals, offers a novel approach to enhancing the wear and corrosion resistance of substrates due to its rapid heating and cooling capabilities, precise control over coating thickness and dilution rates, and non-contact processing characteristics. However, disparities in the physical properties between the coating material and the substrate, coupled with the improper utilization of process parameters, can lead to coating defects, thereby compromising the quality of the coating. This paper examines the effects of material systems and process parameters on laser cladding composite coatings and shows that cracking is mainly caused by thermal and residual stresses. This article summarizes the methods for crack improvement and prevention in five aspects: the selection of processes in the preparation stage, the application of auxiliary fields in the cladding process, heat treatment technology, the use of auxiliary software, and the search for new processes and new structural materials. Finally, the future development trends of laser cladding technology are presented. Full article

The aim of the study was to assess the mechanical and material properties of porous titanium capsules, produced by 3D printing via the DMLS (Direct Metal Laser Sintering) technique based on their potential application as carriers for anticancer drugs. The study used capsules made from the Ti-6Al-4V alloy, and analyzes the impact of geometric parameters, structural features, and printing angles (0°, 45°, and 90°) on their compressive strength. A total of 36 capsules were tested, 18 of type KTD and 18 of type KTM, each in two loading directions. The surface roughness and damage characteristics resulting from mechanical loading have also been evaluated. Statistical analysis of the results was performed using Student’s t-test. The results show that the capsules printed at an angle of 45° are characterized by the highest compressive strength, while their resistance significantly exceeds the values typical of human bone tissue. Additionally, the observed damage does not lead to the formation of sharp edges or loose fragments, which confirms the safety of their use in the body. The high surface roughness promotes tissue integration and limits capsule migration after implantation. The analyses confirm the potential of 3D-printed titanium capsules as effective and safe drug carriers in personalized anticancer therapy. Full article

The strong adsorption capacity of loess poses a significant limitation to the electrokinetic (EK) remediation process. Modified EK technologies, such as graphene oxide-alginate composite hydrogel (GOCH) electrodes, are increasingly employed for the remediation of heavy metal-contaminated loess. However, the complex interactions among multiple physical fields within these modified systems remain poorly understood. This study utilizes COMSOL Multiphysics version 6.0 to simulate diffusion, electromigration, electroosmotic flow, adsorption, and chemical reactions in loess contaminated with copper (Cu) and lead (Pb). A chemical precipitation and ion transport model, governed by the Nernst–Planck equation, was validated through a comparison of simulation results with experimental data. The investigation examines the effects of electrode placement and size on EK efficiency, revealing that diagonally placed irregular electrodes optimize the electric field, minimize ineffective regions, and enhance ion migration. Larger electrodes enhance current density, whereas smaller electrodes mitigate edge shielding effects. This research offers strategic insights into electrode configuration for improved EK remediation of Cu-Pb-contaminated loess, achieving greater efficiency than traditional systems. Full article

Carbon nanotubes (CNTs) functionalized with metal oxides exhibit synergistic properties that enhance their performance across various applications, particularly in electrochemistry. Recent advancements have highlighted the potential of CNT–metal oxide heterostructures, with a specific focus on their electrochemical properties, which are pivotal for applications in sensors, supercapacitors, batteries, and catalytic systems. Among these, nickel oxide (NiO)-modified CNTs have garnered significant attention due to their cost-effectiveness, facile synthesis, and promising gas-sensing capabilities. This study employs quantum-chemical calculations within the framework of density functional theory (DFT) to elucidate the interaction mechanisms between CNTs and NiO. The results demonstrate that the adsorption process leads to the formation of stable CNT-NiO complexes, with detailed analysis of adsorption energies, equilibrium distances, and electronic structure modifications. The single-electron spectra and density of states (DOS) of the optimized complexes reveal significant alterations in the electronic properties, particularly the modulation of the energy gap induced by surface and edge functionalization. Furthermore, the interaction of CNT-NiO composites with acetone (C₃H₆O) and carbon dioxide (CO₂) is modeled, revealing a physisorption-dominated mechanism. The adsorption of these gases induces notable changes in the electronic properties and charge distribution within the system, underscoring the potential of CNT-NiO composites for gas-sensing applications. This investigation provides a foundational understanding of the role of metal oxide modifications in tailoring the sensory activity of CNTs toward trace amounts of diverse substances, including metal atoms, inorganic molecules, and organic compounds. The findings suggest that CNT-NiO systems can serve as highly sensitive and selective sensing elements, with potential applications in medical diagnostics and environmental monitoring, thereby advancing the development of next-generation sensor technologies. Full article

We theoretically investigated two types of nonlinear optical effects of photonic band edges (PBEs) in photonic crystals containing hyperbolic metamaterial (HMM) based on the intensity-dependent phase-variation compensation, where the HMM is composed of alternating the noble metal Ag with large-nonlinear-coefficient and dielectric material. Considering nonlinear conditions, the local field strength variation in nonlinear materials with the increase in the incident angle will lead to the movement of the PBE, resulting in two anomalous optical nonlinear effects. When the PBE is angle-independent under the linear condition, the PCs have angle-sensitive optical bistability and the critical threshold intensity always increases. However, if the PBE is designed to have angle dependence under linear conditions, the optical bistability in the PC can be angle-independent, and the critical threshold intensity is angle-independent over a wide range. This research provides important reference values for manufacturing direction-selectable devices that utilize different kinds of nonlinear optical effects. Full article

Antimony (Sb) is a metalloid widely used in different areas—from the cutting-edge renewable energy technologies to “classical” lead acid batteries. Its availability in primary sources is limited, and these sources are geographically unevenly distributed worldwide. Antimony use will increase in the future. That is why Sb is included in the critical raw material lists of the European Union and the USA. In order to mitigate the future Sb shortage, Sb recovery from industrial residues is worth considering. This paper presents the availability of Sb in nonferrous metals extraction waste and the applicability of the hydrometallurgical route for Sb recovery from such sources. Leaching is emphasized. The use of acidic and alkaline leaching methods, their recent modifications, and the effect of different process parameters (reagents’ type, solid-to-liquid ratio, temperature, and the addition of oxidizing reagents) are highlighted. The use of new leaching systems, such as deep eutectic solvents and non-aqueous solutions, is presented. Initial attempts to apply bioleaching are described. Finally, some proposals for future investigations are given. Full article

The advancement of topology optimization (TO) and additive manufacturing (AM) has significantly enhanced structural design flexibility and the potential for lightweight structures. However, challenges such as intermediate density, mesh dependency, checkerboard patterns, and local extrema in TO can lead to suboptimal performance. Moreover, existing AM technologies confront geometric constraints that limit their application. This study investigates minimum compliance as the objective function and volume as the constraint, employing the solid isotropic material with penalization method, density filtering, and the method of moving asymptotes. It examines how factors like mesh type, mesh size, volume fraction, material properties, initial density, filter radius, and penalty factor influence the TO results for a metallic gooseneck chain. The findings suggest that material properties primarily affect numerical variations along the TO path, with minimal impact on structural configuration. For both hexahedral and tetrahedral mesh types, a recommended mesh size is identified where the results show less than a 1% difference across varying mesh sizes. An initial density of 0.5 is advised, with a filter radius of approximately 2.3 to 2.5 times the average unit edge length for hexahedral meshes and 1.3 to 1.5 times for tetrahedral meshes. The suggested penalty factor ranges of 3–4 for hexahedral meshes and 2.5–3.5 for tetrahedral meshes. The optimal geometric reconstruction model achieves weight reductions of 23.46% and 22.22% compared to the original model while satisfying static loading requirements. This work contributes significantly to the integration of TO and AM in engineering, laying a robust foundation for future design endeavors. Full article

During the electromagnetic launching process, the actual current input into the launcher is obtained by controlling the discharge of the pulsed power supply. Generally, the waveform of the pulse current is determined by the discharge characteristics and discharge time of the pulse power supply. Due to the limitation of control accuracy, the driving current is not an ideal trapezoidal wave, but there is a certain fluctuation (current ripple) in the flat top portion of the trapezoidal wave. The fluctuation of the current will affect the thickness of the liquefied layer at the armature–rail interface as well as the magnitude of the contact pressure, thereby inducing instability at the armature–rail interface and generating micro-arcs, which result in a reduction in the service life of the rails within the launcher. Consequently, it is imperative to conduct an in-depth analysis of the influence of current ripple on the liquefied layer during electromagnetic launching. In this paper, a thermoelastic magnetohydrodynamic model is constructed by coupling temperature, stress, and electromagnetic fields, which are predicated on the Reynolds equation of the metal liquefied layer at the armature–rail contact interface. The effects of current fluctuations on the melting rate of the surface of the armature, the thickness of the liquefied layer, and the hydraulic pressure of the liquefied layer under four different current ripple coefficients (RCs) were analyzed. The results show the following: (1) The thickness and the pressure of the liquefied layer at the armature–rail interface fluctuate with the fluctuation of the current, and, the larger the ripple coefficient, the greater the fluctuations in the thickness and pressure of the liquefied layer. (2) The falling edge of the current fluctuation leads to a decrease in the hydraulic pressure of the liquefied layer, which results in the instability of the liquefied layer between the armature and rails. (3) As the ripple coefficient increases, the time taken for the liquefied layer to reach a stable state increases. In addition, a launching experiment was also conducted in this paper, and the results showed that, at the falling edge of the current fluctuation, the liquefied layer is unstable, and a phenomenon such as the ejection of molten armature and transition may occur. The results of the experiment and simulations mutually confirm that the impact of current fluctuations on the armature–rail interface increases with increases in the ripple coefficient. Full article

In this study, a conceptual turbine blade model with internal cooling channels was designed and fabricated using the selective laser melting (SLM) process. The optimal manufacturing orientation was evaluated through simulations, and the results indicated that vertical orientation yielded the best outcomes, minimizing support material usage and distortion despite increased manufacturing time. Two configurations were produced, namely, an entire-turbine blade model and a cross-sectional model. Non-destructive analyses, including 3D laser scanning for dimensional accuracy, surface roughness measurements, and liquid penetrant testing, were conducted. Visual inspection revealed manufacturing limitations, particularly in the cooling channels at the leading and trailing edges. The trailing edge was too thin to accommodate the 0.5 mm channel diameter, and the channels in the leading edge were undersized and potentially clogged with unmelted powder. The dimensional deviations were within the acceptable limits for the SLM-fabricated metal parts. The surface roughness measurements were aligned with the literature values for metal additive manufacturing. Liquid penetrant testing confirmed the absence of cracks, pores, and lack-of-fusion defects. The SLM is a viable manufacturing process for turbine blades with internal cooling channels; however, significant attention should be paid to the design of additive manufacturing conditions to obtain the best results after manufacturing. Full article

In the nanoindentation testing of metallic materials, mechanical properties often decrease significantly when the indentation position shifts from the central region to the edge due to edge effects, leading to premature edge failure and potential device malfunctions. In this work, molecular dynamic (MD) simulations were conducted to investigate the anisotropic edge effects of nanoindentation on monocrystalline copper with a specific crystal orientation. The results reveal that changes in indentation position strongly influence surface collapse and lateral pile-up behaviors. Notably, edge positions resulted in significant reductions in indentation force and hardness, accompanied by pronounced anisotropy in nanoindentation hardness. Additionally, distinct von Mises stress distributions were observed at different indentation positions, highlighting the crystallographic orientation’s role in modulating edge effects. This study provides new insights into the atomic-scale mechanisms underlying edge effects in metallic materials and their anisotropic characteristics. Full article

The grain boundary diffusion process employing a mixed diffusion source, comprising heavy rare-earth elements and low-melting metals, significantly enhances the coercivity (H_cj) of sintered Nd-Fe-B magnets. In the present study, Tb and Ga were deposited onto the surface of Nd-Fe-B magnets to serve as a diffusion source for improving hard magnetic properties. The effects of varying deposition sequences of Tb and Ga on the magnetic properties and microstructure of the magnets were analyzed. The findings demonstrate that TbF₃ grain boundary diffusion facilitated by Ga effectively increases the efficiency of Tb substitution, leading to enhanced coercivity. When Tb and Ga are deposited simultaneously, coercivity shows a notable improvement of 53.15% compared to the untreated magnet, with no reduction in remanence. Additionally, thermal stability is enhanced, resulting in superior overall magnetic properties. Microstructural analysis reveals that Ga promotes the diffusion of Tb into the magnet. In the magnet where Tb and Ga are co-deposited, the formation of a thinner and more uniform (Nd,Tb)₂Fe₁₄B shell–core structure, along with the greater infiltration depth of Tb, leads to a broader distribution of core–shell structures within the magnet. This effectively increases the anisotropy fields (H_A) of the main phase grains, preventing the nucleation of antiferromagnetic domains at the edges of main-phase grains, thereby enhancing coercivity. Furthermore, the corrosion resistance of the magnet subjected to mixed diffusion is improved. This study provides a foundation for producing highly efficient magnets with a lower content of heavy rare-earth elements. The simplicity and flexibility of the process make it highly suitable for industrial applications. Full article

This article presents a framework of using MEMS sensors to investigate unsteady flow speeds of a flapping wing or the new concept of sensors on flapping wings (SOFWs). Based on the implemented self-heating flow sensor using U18 complementary metal–oxide–semiconductor (CMOS) MEMS foundry provided by the Taiwan Semiconductor Research Institute (TSRI), the compact sensing region of the flow sensor was incorporated for in situ diagnostics of biomimetic flapping issues. The sensitivity of the CMOS MEMS flow sensor, packaged with a parylene coating of 10 μm thick to prolong the lifetime, was observed as −3.24 mV/V/(m/s), which was below the flow speed of 6 m/s. A comprehensive investigation was conducted on integrating CMOS MEMS flow sensors on the leading edge of the mean aerodynamic chord (m.a.c.) of the flexible 70-cm-span flapping wings. The interpreted flow speed signals were checked and demonstrated similar behavior with the (net) thrust force exerted on the flapping wing, as measured in the wind tunnel experiments using the force gauge. The experimental results confirm that the in situ measurements using the concept of SOFWs can be useful for measuring the aerodynamic forces of flapping wings effectively, and it can also serve for future potential applications. Full article

Background: Wear particle reaction is present in every arthroplasty. Sometimes, this reaction may lead to formation of large pseudotumors. As illustrated in this case, the volume of the reaction may be out of proportion to the volume of the wear scar. This case also is the first description of elimination kinetics of systemic titanium exposure caused by wear of a hip arthroplasty. Methods: Case report. Results: A 85-year-old male required revision after total hip arthroplasty due to aseptic loosening of the cup. A massive local adverse reaction to metal and polyethylene debris developed before revision, much larger than the implant damage would intuitively suggest. In this case, in vivo transition in wear mode from edge loading to impingement wear resulted in excessive titanium and polyethylene wear and subsequently a voluminous macrophage reaction and an excessive systemic titanium exposure, with blood concentrations showing a very long elimination half-life of more than two years. Conclusions: The volume of the wear particle reaction is dictated by the volume of the inflammatory cells, not of the wear particles. To the best of our knowledge, this is the first description of elimination kinetics in case of systemic titanium exposure. While the tissue response is caused by a sudden increase of titanium and polyethylene debris, titanium is detectable through whole blood, not serum, analysis and thus be an indicator for risk of failure due to abnormal articulation of the joint replacement. Such measurement may be useful if changes in implant position are detected radiographically. Major elevations of titanium concentrations may require revision, as for any other metal ions. Full article

Owing to the long-standing statement that natural frequency-based crack detection is not sensitive enough to localised damage to identify small cracks, many natural frequency-based crack detection methods are validated by detecting cracks of moderate size. However, a direct comparison between the crack severity causing a measurable natural frequency change and the crack severity reaching the initiation of crack propagation or leading to brittle fracture is constantly ignored. Without this understanding, it is debatable whether the presented crack detection methods are feasible in practical situations. Through natural frequency calculation and linear elastic fracture mechanics, this study is dedicated to filling the above gap in knowledge. To directly utilize the solution of stress intensity factor, common fracture toughness test specimens featuring a single-edge crack are used. These specimens are essentially cracked rectangular plates under uniform uniaxial tension. Considering the stress resultants obtained via the extended finite element method, the natural frequency of the loaded cracked plates is calculated using the Rayleigh–Ritz method incorporating corner functions. In addition, assuming the specimens as structural components under remote uniform tension, the development of critical load versus crack length is derived based on the solution of the stress intensity factor. Thus, critical crack lengths corresponding to a series of safety factors are obtained by equating service load with critical load. After obtaining natural frequencies of the cracked plates with critical crack lengths, the natural frequency drop caused by a critical crack can be computed. Hence, the critical crack length can be compared with the crack length when the frequency drop is measurable. It is found that the brittleness of the employed metals plays a vital role in the feasibility of natural frequency-based crack detection. Full article