Search Results (283)

Origami structures exhibit significant potential for rapid deployment in post-disaster response and temporary architecture due to their ability to quickly fold and deploy. Further development of these structures into modular components that can be assembled into large-scale architectural systems holds great importance for the fields of architecture and civil engineering. In this study, a thin-walled foldable column was developed based on the “pillow box” origami pattern. This column maintains its three-dimensional configuration during folding, owing to its inherent self-locking characteristic. Two crease-weakening strategies (“dashed-line” and “slit-hole”) were proposed and experimentally validated. A systematic numerical study was conducted to investigate the axial compressive performance of pillow box columns with weakened curved creases. The results indicate that both weakening strategies effectively enable folding while preserving global integrity under compression. The pillow box column with “dashed-line” creases (OCC-D) demonstrated superior load-bearing capacity, with a load-to-weight ratio of up to 658.9, nearly twice that of the corresponding conventional square tube. Parametric analysis of the crease geometry further revealed that increasing the number of crease units enhances the load-bearing performance, and the optimal performance is achieved when the spacing between slit openings equals the slit length ($l_h=l_c$). These findings highlight the advantages of pillow box origami columns as thin-walled load-bearing components, offering new insights for the rapid construction and lightweight design of architectural structures. Full article

The secondary air system plays important roles in gas turbines, such as cooling hot-end components, sealing the rim, and balancing axial forces. In this paper, the flow structure and the heat transfer characteristics of the rotating disk cavity with two inlets and single outlet is studied by CFD (Computational Fluid Dynamics) approach. The effect and mechanism under higher rotational speed and larger mass flow rate are also discussed. The results show that a large-scale vortex is induced by the central inlet jet in the low-radius region of the cavity, while the flow structure in the high-radius region is significantly influenced by rotational speed and flow rate. Increasing the rotational speed generally enhances heat transfer because it amplifies the differential rotational linear velocity between the disk surface and nearby wall flow, consequently thinning the boundary layer. Increasing the mass flow rate enhances heat transfer through two primary mechanisms: firstly, it elevates the turbulence intensity of the near-wall fluid; secondly, the higher radial velocity results in a thinner boundary layer. Full article

Ensuring the long-term integrity of structural materials in extreme environments is a critical challenge in the design of equipment for nuclear fuel cycle operations. In particular, the durability of materials exposed to high temperatures and chemically aggressive environments during the processing of irradiated reactor components remains a key concern. This study investigates the high-temperature corrosion behavior of 12Cr18Ni10Ti austenitic stainless steel in the reaction chamber of a beryllium chlorination plant developed for recycling irradiated beryllium reflectors from the JMTR (Japan Materials Testing Reactor). The chlorination process was conducted at temperatures ranging from 500 °C to 1000 °C in a chlorine-rich atmosphere. Post-operation analysis of steel samples extracted from the chamber revealed that uniform wall thinning was the predominant degradation mechanism. However, in high-temperature regions near the heating element, localized forms of damage, specifically pitting and intergranular corrosion, were detected, indicating that thermal stresses exacerbated localized attack. These findings contribute to the assessment of the service life of structural components under extreme conditions and offer practical guidance for material selection and design optimization in high-temperature chlorination systems used in nuclear applications. Full article

Monitoring dopamine (DA) has attracted increasing attention due to alterations in DA levels associated with brain disorders. In addition, the urinary DA concentration plays a significant role in the sympathoadrenal system. A decrease in DA can impair reward-seeking behavior and cognitive flexibility. Therefore, accurate and precise DA detection is necessary. In this study, a poly(3-aminobenzylamine)/functionalized multi-walled carbon nanotube (PABA/f-CNT) composite thin film was fabricated by electrochemical synthesis, or electropolymerization, of 3-aminobenzylamine (3-ABA) monomer and f-CNTs through cyclic voltammetry (CV) on a fluorine-doped tin oxide (FTO)-coated glass substrate, which also served as a working electrode for label-free DA detection in artificial urine. The formation of the film was confirmed by the obtained cyclic voltammogram, electrochemical impedance spectroscopy (EIS) plots, and scanning electron microscope (SEM) and transmission electron microscope (TEM) images. The chemical components of the films were analyzed using attenuated total reflection–Fourier transform infrared (ATR–FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). For label-free DA detection, various concentrations (50–1000 nM) of DA were determined in buffer solution through differential pulse voltammetry (DPV). The fabricated PABA/f-CNT film presented two linear ranges of 50–400 nM (R² = 0.9915) and 500–1000 nM (R² = 0.9443), with sensitivities of 1.97 and 0.95 µA·cm⁻²·µM⁻¹, respectively. The limit of detection (LOD) and the limit of quantity (LOQ) were 119.54 nM and 398.48 nM, respectively. In addition, the PABA/f-CNT film provided excellent selectivity against common interferents (ascorbic acid, uric acid, and glucose) with high stability, reproducibility, and repeatability. For potential future medical applications, DA detection was further performed in artificial urine, yielding a high percentage of recovery. Full article

Laser-directed energy deposition (DED) offers significant potential for the additive manufacturing of thin-walled Inconel 718 aerospace components. However, the structural defects readily formed during deposition, along with the extensive precipitation of long-chain Laves phases between coarse dendrites, can severely compromise the mechanical properties of as-fabricated Inconel 718 parts. To address this, an ultrasonic-assisted DED (UDED) method was employed to reduce the deposited structural defects and refine crystalline structures, and the influences of ultrasonic energy fields on the microstructure and mechanical properties of thin-walled Inconel 718 samples were systematically investigated. The results demonstrated that ultrasonic vibration significantly enhances the microstructural quality by reducing porosity and pore size, weakening texture intensity, fragmenting long-chain Laves phases, mitigating severe elemental segregation, and refining matrix grains. Consequently, the UDED thin-walled Inconel 718 sample exhibited an approximately 15% increase in microhardness compared to the conventional DED counterpart, alongside satisfactory strength and ductility. This study highlights the superiority of UDED for microstructure tailoring and its potential for mechanical property regulations in thin-walled Inconel 718 aerospace components. Full article

This study aimed to optimize the grain structure of complex thin-walled nickel-based superalloy castings by investigating the influence of key casting parameters using both cellular automaton–finite element (CAFE) simulations and experimental validation. The main problem addressed was the inhomogeneous grain morphology arising from complex mold geometries and uneven thermal conditions during investment casting. The solidification process was simulated using the ProCAST software, incorporating the CAFE method to model temperature fields and grain growth dynamics. The results revealed that the molten metal flow pattern during mold filling significantly affected the local temperature field and subsequent grain formation. Specifically, simultaneous bidirectional filling minimized thermal gradients and suppressed coarse columnar grain formation, promoting finer, more uniform equiaxed grains. Lowering the pouring temperature (to 1430 °C) in combination with reduced shell temperature (600–800 °C) enhanced nucleation and improved grain uniformity in thin-walled regions. Higher cooling rates also refined the grain structure by increasing undercooling and limiting grain growth. Experimental castings confirmed these simulation outcomes, demonstrating that the proposed optimization strategies can significantly improve grain homogeneity in critical structural areas. These findings provide a practical approach for controlling microstructure in large, intricate superalloy components through targeted process parameter tuning. Full article

AI-integrated robotics in Industry 5.0 demands advanced manufacturing systems capable of autonomously interpreting complex geometries and dynamically adjusting machining strategies in real time—particularly when dealing with aerospace components featuring large-curvature surfaces. Large-curvature aerospace components present significant challenges for precision drilling due to surface-normal deviations caused by curvature, roughness, and thin-wall deformation. This study presents a robotic drilling system that integrates adaptive PCA-based surface normal estimation with in-process pre-drilling correction and post-drilling verification. This system integrates a 660 nm wavelength linear laser projector and a 1.3-megapixel industrial camera arranged at a fixed 30° angle, which project and capture structured-light fringes. Based on triangulation, high-resolution point clouds are reconstructed for precise surface analysis. By adaptively selecting localized point-cloud regions during machining, the proposed algorithm converts raw measurements into precise normal vectors, thereby achieving an accurate solution of the normal direction of the surface of large curvature parts. Experimental validation on a 400 mm-diameter cylinder shows that using point clouds within a 100 mm radius yields deviations within an acceptable range of theoretical normals, demonstrating both high precision and reliability. Moreover, experiments on cylindrical aerospace-grade specimens demonstrate normal direction accuracy ≤ 0.2° and hole position error ≤ 0.25 mm, maintained across varying curvature radii and roughness levels. The research will make up for the shortcomings of existing manual drilling methods, improve the accuracy of hole-making positions, and meet the high fatigue service needs of aerospace and other industries. This system is significant in promoting the development of industrial automation and improving the productivity of enterprises by improving drilling precision and repeatability, enabling reliable assembly of high-curvature aerospace structures within stringent tolerance requirements. Full article

Spherical shells exhibit superior strength-to-geometry efficiency, making them ideal for industrial applications such as fluid storage tanks, architectural domes, naval vehicles, nuclear containment systems, and aeronautical and aerospace components. Given their critical role, careful attention to the design parameters and engineering constraints is essential. The present paper investigates the buckling responses of bio-inspired helicoidal laminated composite spherical shells under normal and torsional loading, including the effects of a Winkler elastic medium. The pre-buckling equilibrium equations are derived using linear three-dimensional (3D) elasticity theory and the principle of virtual work, solved via the classical finite element method (FEM). The buckling load is computed using a nonlinear Green strain formulation and a generalized geometric stiffness approach. The shell material employed in this study is a T300/5208 graphite/epoxy carbon fiber-reinforced polymer (CFRP) composite. Multiple helicoidal stacking sequences—linear, Fibonacci, recursive, exponential, and semicircular—are analyzed and benchmarked against traditional unidirectional, cross-ply, and quasi-isotropic layups. Parametric studies assess the effects of the normal/torsional loads, lamination schemes, ply counts, polar angles, shell thickness, elastic support, and boundary constraints on the buckling performance. The results indicate that quasi-isotropic (QI) laminate configurations exhibit superior buckling resistance compared to all the other layup arrangements, whereas unidirectional (UD) and cross-ply (CP) laminates show the least structural efficiency under normal- and torsional-loading conditions, respectively. Furthermore, this study underscores the efficacy of bio-inspired helicoidal stacking sequences in improving the mechanical performance of thin-walled composite spherical shells, exhibiting significant advantages over conventional laminate configurations. These benefits make helicoidal architectures particularly well-suited for weight-critical, high-performance applications in aerospace, marine, and biomedical engineering, where structural efficiency, damage tolerance, and reliability are paramount. Full article

The increased use of prefabricated assembly technology promotes the transformation of urban subway construction in the lightweight direction, in which the closed cavity thin-walled component is increasingly widely used in underground structures due to its excellent material efficiency benefits. In order to investigate the effect of closed cavity thin-walled components, numerical models of a seven-ring solid structure and cavity structure were constructed based on the four-block prefabricated metro station of Qingdao Metro Line 9, Chengzi Station. This study considers the longitudinal effect between rings and compares the nonlinear force and deformation characteristics of both structures under the load of self-weight and use stage. The study indicates that incorporating closed cavities within structures reduces internal forces in most sections while increasing principal strain, displacement, and stress. As the applied load increases, the rate of internal force reduction diminishes, and the increment of displacement deformation also decreases. Shear lag effects occur in closed cavity sections, leading to a non-uniform normal stress distribution, with maximum shear stress appearing at rib intersections. The cavity location, mortise–tenon joints, and columns represent critical locations for deformation and force transmission within cavity structures. Optimization design must prioritize ensuring their deformation resistance and load-bearing capacity to enhance the overall structural integrity, safety, and reliability. Full article

This study investigates the microstructure evolution and mechanical properties of DSS2209 duplex stainless steel fabricated via cold metal transfer wire arc additive manufacturing (CMT-WAAM). The as-deposited thin-wall components exhibit significant microstructural heterogeneity along the build height due to thermal history variations. Optical microscopy, SEM-EDS, and EBSD analyses reveal distinct phase distributions: the bottom region features elongated blocky austenite with Widmanstätten austenite (WA) due to rapid substrate-induced cooling; the middle region shows equiaxed blocky austenite with reduced grain boundary austenite (GBA) and WA, attributed to interlayer thermal cycling promoting recrystallization and grain refinement (average austenite grain size: 4.16 μm); and the top region displays coarse blocky austenite from slower cooling. Secondary austenite (γ₂) forms in interlayer remelted zones with Cr depletion, impacting pitting resistance. Mechanical testing demonstrates anisotropy; horizontal specimens exhibit higher strength (UTS: 610 MPa, YS: 408 MPa) due to layer-uniform microstructures, while vertical specimens show greater ductility (elongation) facilitated by columnar grains aligned with the build direction. Hardness ranges uniformly between 225–239 HV. The study correlates process-induced thermal gradients (e.g., cooling rates, interlayer cycling) with microstructural features (recrystallization fraction, grain size, phase morphology) and performance, providing insights for optimizing WAAM of large-scale duplex stainless steel components like marine propellers. Full article

The aim of this study was to determine the influence of heat treatment parameters on the microstructure and mechanical properties of the AlMn1Cu (EN AW-3003) aluminium alloy with a one-sided cladding layer of AlSi7.5 alloy (EN AW-4343). The investigation was conducted within an annealing temperature range of 200 °C to 500 °C, analysing changes in hardness, mechanical strength, formability, and planar anisotropy. The results clearly indicate that within the temperature range of 300–340 °C, an intensive process of static recrystallisation occurs, leading to the restoration of a fine-grained and homogeneous microstructure. This is accompanied by a sharp reduction in hardness and yield strength, along with a significant increase in ductility and deep drawing capability. A notable reduction in the anisotropy of plastic properties was also observed, confirming effective homogenisation of the material’s microstructure. The findings unambiguously demonstrate that heat treatment within the range of 300–500 °C enables the formation of an isotropic microstructure with low hardness and high formability, rendering the material particularly suitable for shaping thin-walled components, including heat exchangers. Full article

Most existing assembly accuracy analysis methods focus on rigid assemblies or assume assemblies to be rigid bodies, neglecting the influence of assembly deformation in weak rigid components (WRCs) such as thin-walled structures, cantilever structures, etc. As a result, the assembly accuracy analysis becomes inaccurate, and the accuracy of key components cannot be effectively controlled. This may lead to serious issues such as forced assembly, repair, and rework. To address these problems, this study proposes a rigid–flexible coupling-based assembly accuracy analysis method for WRCs. The stiffness matrix and assembly deformation of WRCs are calculated, and by coupling assembly deformation with other assembly deviations, a rigid–flexible coupling assembly accuracy data model is established. This model incorporates multiple deviation sources, including assembly process variations, design tolerances, and assembly deformations. Assembly deviation transfer modeling and accumulation calculation methods for WRCs are investigated, enabling assembly accuracy simulation and statistical analysis. A case study on WRC assembly accuracy analysis is conducted, and the results demonstrate that the proposed method improves the accuracy of assembly analysis for WRCs, verifying its reliability. Full article

High-strength steel has high strength and low thermal conductivity, and its thin-walled parts are very susceptible to residual stress and deformation caused by cutting heat during the drilling process, which affects the machining accuracy and quality. High-strength steel thin-walled components are widely used in aerospace and other high-end sectors; however, systematic investigations into their temperature fields during drilling remain scarce, particularly regarding the evolution characteristics of the temperature field in thin-wall drilling and the quantitative relationship between drilling parameters and these temperature variations. This paper takes the thin-walled parts of AF1410 high-strength steel as the research object, designs a special fixture, and applies infrared thermography to measure the bottom surface temperature in the thin-walled drilling process in real time; this is carried out in order to study the characteristics of the temperature field during the thin-walled drilling process of high-strength steel, as well as the influence of the drilling dosage on the temperature field of the bottom surface. The experimental findings are as follows: in the process of thin-wall drilling of high-strength steel, the temperature field of the bottom surface of the workpiece shows an obvious temperature gradient distribution; before the formation of the drill cap, the highest temperature of the bottom surface of the workpiece is distributed in the central circular area corresponding to the extrusion of the transverse edge during the drilling process, and the highest temperature of the bottom surface can be approximated as the temperature of the extrusion friction zone between the top edge of the drill and the workpiece when the top edge of the drill bit drills to a position close to the bottom surface of the workpiece and increases with the increase in the drilling speed and the feed volume; during the process of drilling, the highest temperature of the bottom surface of the workpiece is approximated as the temperature of the top edge of the drill bit and the workpiece. The maximum temperature of the bottom surface of the workpiece in the drilling process increases nearly linearly with the drilling of the drill, and the slope of the maximum temperature increases nearly linearly with the increase in the drilling speed and feed, in which the influence of the feed on the slope of the maximum temperature increases is larger than that of the drilling speed. Full article

Channels with three standard symmetrical sections and one asymmetric section are mounted as cantilever beams with the web oriented vertically. A classical solution to the analysis of stress in each thin-walled cantilever channel is provided using the principle of wall shear flow superposition. The latter is coupled with a further superposition between axial stress arising from bending and from the constraint placed on free warping imposed at the fixed end. Closed solutions for design are tabulated for the net shear stress and the net axial stress at points around any section within the length. Stress distributions thus derived serve as a benchmark structure for alternative numerical solutions and for experimental investigations. The conversion of the transverse free end-loading applied to a thin-walled cantilever channel into the shear and axial stress that it must bear is outlined. It is shown that the point at which this loading is applied within the cross-section is crucial to this stress conversion. When a single force is applied to an arbitrary point at the free-end section, three loading effects arise generally: bending, flexural shear and torsion. The analysis of each effect requires that this force’s components are resolved to align with the section’s principal axes. These forces are then considered in reference to its centroid and to its shear centre. This shows that axial stress arises directly from bending and from the constraint imposed on free warping at the fixed end. Shear stress arises from flexural shear and also from torsion with a load offset from the shear centre. When the three actions are combined, the net stresses of each action are considered within the ability of the structure to resist collapse from plasticity and buckling. The novelty herein refers to the presentation of the shear flow calculations within a thin wall as they arise from an end load offset from the shear centre. It is shown how the principle of superposition can be applied to individual shear flow and axial stress distributions arising from flexural bending, shear and torsion. Therein, the new concept of a ‘trans-moment’ appears from the transfer in moments from their axes through centroid G to parallel axes through shear centre E. The trans-moment complements the static equilibrium condition, in which a shift in transverse force components from G to E is accompanied by torsion and bending about the flexural axis through E. Full article

The use of aluminum honeycomb structures is fast expanding in advanced sectors such as the aeronautics, aerospace, marine, and automotive industries. However, processing these structures represents a major challenge for producing parts that meet the strict standards. To address this issue, an innovative manufacturing method using longitudinal ultrasonic vibration-assisted cutting, combined with a CDZ10 hybrid cutting tool, was developed to optimize the efficiency of traditional machining processes. To this end, a 3D numerical model was developed using the finite element method and Abaqus/Explicit 2017 software to simulate the complex interactions among the cutting tool and the thin walls of the structures. This model was validated by experimental tests, allowing the study of the influence of milling conditions such as feed rate, cutting angle, and vibration amplitude. The numerical results revealed that the hybrid technology significantly reduces the cutting force components, with a decrease ranging from 10% to 42%. In addition, it improves cutting quality by reducing plastic deformation and cell wall tearing, which prevents the formation of chips clumps on the tool edges, thus avoiding early wear of the tool. These outcomes offer new insights into optimizing industrial processes, particularly in fields with stringent precision and performance demands, like the aerospace sector. Full article