Search Results (2,171)

The non-uniform temperature distribution in ballastless track slabs under complex meteorological conditions can induce structural defects, threatening the safety of high-speed railways. Existing temperature field models often rely on idealized geometric and meteorological assumptions, thereby constraining a fine-grained and quantitative resolution of the independent thermal effects governed by key boundary conditions. To address this, the current study proposes a temperature field analysis method integrating high-precision geometry and physical processes: the actual track geometry is reconstructed via 3D laser scanning point clouds, and a 3D transient heat conduction finite element model is developed by incorporating measured meteorological data and an astronomical model for dynamic solar radiation calculation. Results demonstrate close agreement between simulations and field measurements (MAPE < 5%, R² > 0.92), validating the model’s accuracy. Further analysis reveals that the box girder substructure, due to the “air cavity heat accumulation effect,” causes greater temperature fluctuations at the slab bottom compared to the subgrade, increasing the maximum positive temperature gradient by approximately 9%. The track alignment significantly influences temperature distribution, with the east–west alignment (0°) exhibiting a peak surface temperature 1.30 °C higher than the north–south alignment (90°) and instantaneous temperature differences reaching up to 2.4 °C. This study delivers the first dedicated, quantitative analysis of the impact of track substructure and alignment on the temperature field of the slab, providing a theoretical basis for the differentiated design of ballastless tracks and the revision of temperature load standards. Full article

This paper presents a numerical study of fluid–structure interaction (FSI) applied to wind turbines, combining computational fluid dynamics (CFD) and finite element analysis (FEA). The study focuses on a 3D wind turbine blade inspired by the GE 1.5XLE model. The blade features a twisted geometry with S818, S825, and S826 aerodynamic profiles, and is made of an orthotropic composite material with variable thickness and an internal spar. The fluid domain is defined by two circular sections upstream and downstream, aligned along the Z-axis. Simulations are performed under a wind speed of 12 m/s and a rotational speed of −2.22 rad/s (Tip Speed Ratio (TSR) = 8), with air modeled as an incompressible fluid at ambient temperature. On the CFD side, a periodic and symmetric modeling approach is applied, reducing the fluid domain to one-third of the full configuration by simulating flow around a single blade and extrapolating results to the remaining ones. This method achieves a 47% reduction in computation time while maintaining high accuracy in aerodynamic results. On the FEA side, spar condensation is performed by creating a superelement using the substructuring method. This strategy reduces structural computation time by 45% while preserving reliable predictions of displacements, stresses, and natural frequencies. These results confirm the effectiveness of the proposed techniques for accurate and computationally efficient aeroelastic simulations. Full article

Soil compaction in grassland and agricultural soils reduces water infiltration, root growth and ecosystem services. Conventional deep tillage and coring can alleviate compaction but are energy intensive and strongly disturb the turf. This study proposes an earthworm-inspired subsurface robot as a low-disturbance loosening tool for compacted grassland soils. Design principles are abstracted from earthworm body segmentation, anchoring–propulsion peristaltic locomotion and corrugated body surface, and mapped onto a robotic body with anterior and posterior telescopic units, a flexible mid-body segment, a corrugated outer shell and a brace-wire steering mechanism. Kinematic simulations evaluate the peristaltic actuation mechanism and predict a forward displacement of approximately 15 mm/cycle. Using the finite element method and a Modified Cam–Clay soil model, different linkage layouts and outer-shell geometries are compared in terms of radial soil displacement and drag force in cohesive loam. The optimised corrugated outer shell combining circumferential and longitudinal waves lowers drag by up to 20.1% compared with a smooth cylinder. A 3D-printed prototype demonstrates peristaltic locomotion and steering in bench-top tests. The results indicate the potential of earthworm-inspired subsurface robots to provide low-disturbance loosening in conservation agriculture and grassland management, and highlight the need for field experiments to validate performance in real soils. Full article

Cerebral palsy (CP) often causes mobility limitations that require assistive devices such as Ankle Foot Orthoses (AFOs) to enhance functional stability. This study aims to develop an optimized 3D-printed AFO design that improves comfort, structural durability, and production efficiency for children with CP. The research applies a Design of Experiment approach using the Taguchi method to optimize 3D printing parameters, supported by tensile testing to identify the best material configuration. Design alternatives were prioritized using the Analytical Hierarchy Process, while Finite Element Analysis was conducted to evaluate mechanical performance under physiological loading. The selected PETG configuration (33% infill density and 0.15 mm layer thickness) demonstrated improved tensile strength and flexibility, contributing to enhanced structural behavior. A prototype was produced and validated using the Quebec User Evaluation of Satisfaction with Assistive Technology (QUEST) questionnaire. Results showed higher overall user satisfaction for the optimized 3D-printed AFO compared to conventional devices, particularly in safety, comfort, and durability. The integration of optimized material parameters, systematic design evaluation, and user-centered assessment provides an effective pathway toward improving AFO performance and supporting the mobility and quality of life of children with cerebral palsy. Full article

Selective laser melting (SLM) is a 3D printing technology for precision manufacturing. Owing to its high forming accuracy, parts fabricated by SLM can often be used directly without secondary machining. Consequently, the stress field in the structure, especially local stress concentration in small regions, is of great importance. Building on our previous work, this study proposes an accurate and efficient thermo-mechanical analysis method that combines a computational fluid dynamics (CFD) model and a finite element method (FEM) model for stress prediction in micrometer-scale SLM. Compared with the conventional element birth–death method, the present model more faithfully reproduces the SLM process and the post-solidification morphology and stress distribution. Numerical simulation of a single-track TC4 scan shows that pronounced surface undulations and lack-of-fusion regions exhibit significant stress concentration: the local residual stress can reach approximately 900 MPa, whereas regions with relatively smooth surface geometry exhibit stresses of about 650 MPa. This indicates a clear positive correlation between surface quality and stress concentration. The results provide a new theoretical basis for understanding defect formation mechanisms, spatial stress distribution, and scan-path optimization in SLM components. Full article

Multistage hydraulic fracturing enhances recovery from low-permeability reservoirs. Understanding stress shadow effects and fracture reorientation is essential for optimizing multistage fracturing. This study develops a fully coupled 3D hydromechanical model based on the finite–discrete element method (FDEM) to simulate echelon hydraulic fractures in dual-well systems under varying well spacings and initial perforation lengths. Results show that fracture interactions are highly sensitive to spacing and initiation asymmetry. Closely spaced fractures generate strong stress shadows, influencing propagation depending on geometry and timing. A theoretical model incorporating induced stress and the weight function further clarifies stress shadow mechanisms, introducing disturbance factors to describe promotion or inhibition effects between fractures. The findings reveal an optimal well spacing that maximizes fracture complexity and reservoir stimulation, while pronounced initiation asymmetry leads to dominant–subordinate propagation and reduced efficiency. This integrated framework improves understanding of fracture evolution and guides fracturing optimization in tight formations. Full article

The modern coinage industry ensures dimensional and weight precision, as well as improved surface quality, for its products. The speed of coin mass production requires increased performance for used machines and tools. Despite these, error incidence cannot be excluded. Some of these errors are recorded inside the punching machine and generate clipped blank disks; on their turn, those malformed disks lead to the clipped coins. In the first part, the paper presents the premises underlying the appearance of clipped blanks. There are some exemplified coins having different types of clips: curved, straight, and ragged. The literature review in the coinage field covers the following subjects: coin and die behavior under the striking load, viewpoints on 3D modeling, and finite element method (FEM) analysis, insights on various striking errors, with most of them more or less valued as collection metal pieces. The paper’s main purpose is outlined as follows: to study, using the available modern techniques, the particularities of different clipped coin types. In the second part of the paper, we introduced the adequate tridimensional (3D) model, for parts such as the die, collar, and the coin. It follows the assembled model corresponding to each studied case, which consists of the obverse and reverse striking dies and the collar, having inside them the coin. For each of the models, based on the initial conditions, the finite element analysis was performed. The paper’s last part presents the analysis’ results, the discussions, and the conclusions. Full article

This manuscript presents a reinforcement learning (RL) agent method to optimize the geometry of a coaxial magnetic gear using a 2D finite element magnetic (FEM) simulation. The proposed optimization algorithm aims to improve the maximum torque within given boundaries of the magnetic gear geometry by adjusting parameterized radii. A linear actor–critic gradient algorithm is implemented, where the actor learns a policy to adjust and discover the values of five geometric parameters of the magnetic gear model, and the critic evaluates the performance of the resulting designs. The RL agent interacts with an environment integrated with a 2D FEM simulation, which provides feedback by calculating the total torque of the new geometry discovered. The optimization algorithm uses a greedy exploration method that uses the total torque as a reward system, which the RL agent aims to maximize. The results obtained for the magnetic gear optimization demonstrate the effectiveness of the proposed RL algorithm, which can be applied to automate multiparameter geometric optimization using artificial intelligence systems. Full article

A novel anti-resonant hollow-core fiber (AR-HCF) is proposed. The fiber uses cross-nested circular cladding tubes including single-nested and non-nested tubes in the near-infrared spectral region of 1.3–1.7 μm. All the anti-resonant tubes are used to minimize the confinement loss (CL) of the LP₀₁ core mode. The non-nested tubes are also employed to achieve single-mode performance through strong mode coupling between the cladding mode and the LP₁₁ core mode. The impact of the structural parameters on the CL of the modes is analyzed by using the finite element method (FEM). Optimization results indicate that the CLs of the LP₀₁ mode and the LP₁₁ mode are 0.18 dB/km and 5.88 × 10³ dB/km at 1.55 μm. Consequently, the higher-order mode extinction ratio (HOMER) achieves 3.27 × 10⁴. Additionally, the mode field area of the fiber exceeds 4720 μm² and the corresponding mode field diameter of the LP₀₁ mode is more than 77 μm across the spectral region of 1.3–1.7 μm. In the practical applications, the fabrication tolerance is analyzed. The collapse of anti-resonant tubes within 0–2 μm and positional offsets between 0° and 4° both have minimal impact on fiber performance, thereby ensuring the stability of the system. Compared with other reported fibers, the proposed fiber demonstrates superior performance. Full article

The accurate modelling of material removal mechanisms in grinding processes requires precise constitutive equations describing dynamic material behaviour under extreme strain rates and large deformations. This study presents a novel methodology for optimising the Johnson–Cook (J–C) constitutive model parameters for micro-grinding applications, addressing the limitations of conventional mechanical testing at strain rates exceeding 10⁵ s⁻¹. The research employed single abrasive grain micro-cutting experiments using a diamond Vickers indenter on aluminium alloy 7075-T6 specimens. High-resolution topographic measurements (130 nm lateral resolution) were used to analyse the scratch geometry and lateral material displacement patterns. Ten modified J–C model variants (A1–A10) were systematically evaluated through finite element simulations, focusing on parameters governing plastic strengthening (B, n) and strain rate sensitivity (C). Quantitative non-conformity criteria assessed agreement between experimental and simulated results for cross-sectional areas and geometric shapes of material pile-ups and grooves. These criteria enable an objective evaluation by comparing the pile-up height (h), width (l), and horizontal distance to the peak (d). The results demonstrate that conventional J–C parameters from Hopkinson bar testing exhibit significant discrepancies in grinding conditions, with unrealistic stress values (17,000 MPa). The optimised model A3 (A = 473 MPa, B = 80 MPa, n = 0.5, C = 0.001) achieved superior convergence, reducing the non-conformity criteria to Σk_A = 0.46 and Σk_K = 1.16, compared to 0.88 and 1.67 for the baseline model. Strain mapping revealed deformation values from ε = 0.8 to ε = 11 in lateral pile-up regions, confirming the necessity of constitutive models describing material behaviour across wide strain ranges. The methodology successfully identified optimal parameter combinations, with convergence errors of 1–14% and 7–60% on the left and right scratch sides, respectively. The approach provides a cost-effective alternative to expensive dynamic testing methods, with applicability extending to other ductile materials in precision manufacturing. Full article

The Inverse Finite Element Method (iFEM) is a valuable tool for reconstructing displacement fields from strain measurements, making it ideal for structural health monitoring. Traditional iFEM approaches are deterministic and typically require dense sensor networks for accurate results. However, practical constraints—such as limited sensor placement and cost—call for robust extrapolation techniques to estimate strain in non-instrumented regions. This paper proposes a stochastic 1D iFEM framework that integrates uncertainty quantification into the strain extrapolation process. By assigning confidence weights to extrapolated values, the method enhances the reliability of displacement reconstruction in sparsely instrumented structures. The approach is validated through numerical and experimental studies, demonstrating improved accuracy and robustness compared to traditional interpolation methods, even under varying loading conditions. The results confirm the method’s suitability for real-world applications in aerospace, civil, and naval engineering, particularly when direct strain measurements are limited. Full article

This article compares the results of numerical and experimental analysis of the mechanical properties of an optimized 3D-printed beam. The samples were subjected to a four-point bending test, and corresponding numerical models were created at the same time. The beams were printed using 3D printing and their weight was reduced by using an internal spatial grid with variable thickness that gradually increases towards the outer walls. This approach allows for effective optimization of material strength while minimizing raw material consumption during production. One of the key findings is the determination of the ultimate strength between fibers, the mode of failure, and the high agreement between the experimental results and the numerical model using the finite element method. The optimized beam achieved nearly 60% weight reduction while maintaining comparable load-bearing capacity. The knowledge gained opens up new possibilities in the field of materials engineering and also makes a significant contribution to the methodology of developing and optimizing these structures using 3D printing technology. Full article

Permanent Magnet Synchronous Generators (PMSGs) have become increasingly important in industrial applications such as wind turbine systems due to their high efficiency and power density. However, their operational reliability can be affected by asymmetries such as static eccentricity (SE) and load current unbalance (UnB), which exhibit similar spectral features and are therefore difficult to differentiate using conventional techniques such as Motor Current Signature Analysis (MCSA). Stray flux analysis provides an alternative diagnostic approach, yet single-point measurements often lack the sensitivity required for accurate fault discrimination. This study introduces a diagnostic methodology based on the Space Vector Stray Flux (SVSF) for identifying static eccentricity (SE) and load current unbalance (UnB) faults in PMSG-based systems. The SVSF is derived from three external stray flux sensors placed 120° electrical degrees apart and analyzed through symmetrical component decomposition, focusing on the +5f_s positive-sequence harmonic. Two-dimensional Finite Element Analysis (FEA) conducted on a 36-slot/12-pole PMSG model shows that the amplitude of the +5f_s harmonic increases markedly under static eccentricity, while it remains nearly unchanged under load current unbalance. To validate the simulation findings, comprehensive experiments have been conducted on a dedicated test rig equipped with high-sensitivity fluxgate sensors. The experimental results confirm the robustness of the proposed SVSF method against practical constraints such as sensor placement asymmetry, 3D axial flux effects, and electromagnetic interference (EMI). The identified harmonic thus serves as a distinct and reliable indicator for differentiating static eccentricity from load current unbalance faults. The proposed SVSF-based approach significantly enhances the accuracy and robustness of fault detection and provides a practical tool for condition monitoring in PMSG. Full article

To explore the potential of new information transmission windows, this work presents a broadband plasmonic filter based on gold-deposited silicon photonic crystal fiber (PCF) operating in mid-infrared regime numerically, using the finite element method (FEM). The simulation results indicate that the interaction between the high-refractive-index pure silicon material and the gold layer can cause a shift of the resonance central point to the mid-infrared band, which provides the prerequisite for mid-infrared filtering. When the cladding holes’ diameter is 1.3 µm, the inner holes’ diameter is 1.04 µm, the diameter of the holes located on both sides of the core region is 2.08 µm, the gold-coated holes’ diameter is 2.08 µm, the lattice constant is 2 µm, and the gold thickness is 50 nm, this PCF can operate in the mid-infrared band near the central wavelength of 3 µm. The 1 mm long PCF polarizer exhibits a maximum extinction ratio (ER) of −43.5 dB at 3 µm and a broad operating bandwidth of greater than 820 nm with ER better than −20 dB. Additionally, it also possesses high fabrication feasibility. This in-fiber polarization filter, characterized by its comprehensive performance and ease of fabrication, aids in exploring the development potential of high-speed and large-capacity modern communication networks within new optical bands and contributes to new photonic computing and sensing. Full article

This study numerically investigates the deformation and consolidation behavior of high-water-content river sediment improved by a combined vacuum preloading and internal air-bag pressurization (VPA) system. A 2D axisymmetric finite-element model in Abaqus 2021 with the Modified Cam-Clay constitutive law is established to simulate the treatment process. Key design parameters—air-bag pressure, pressurization timing, embedment depth, and staged loading—are systematically analyzed. Results show that: (1) Under a −80 kPa vacuum, an additional 20 kPa air-bag pressure reduces the maximum inward horizontal displacement by over 20%, while effective stress increases linearly with pressure; (2) Early pressurization (20 days) better controls lateral deformation and accelerates strength gain; (3) Staged pressurization (20 kPa upper, 40 kPa lower) outperforms uniform loading in both displacement control and cost-effectiveness; (4) Compared to 30 kPa surcharge preloading, VPA further reduces horizontal displacement by 10–18% under equivalent total load. The hybrid “vacuum–air-bag–surcharge” scheme yields the highest effective stress and smallest lateral deformation. The VPA method enhances sediment engineering properties, providing a viable approach for resource utilization of dredged materials. Full article