Engineering

Abstract: The high energy consumption of conventional mixers equipped with active mixing elements necessitates the development of more efficient technologies for mixing bulk materials and feed mixtures. This study proposes a gravity-based mixing method based on the rotation of an inclined cylindrical chamber without the use of active mixing elements. During rotation, the mixture components move toward both end walls of the chamber and simultaneously perform circular motion along the inner cylindrical surface, which intensifies the mixing process and reduces energy consumption. A structural and technological design of the gravity mixer was developed, and an experimental prototype was manufactured. Analytical relationships were obtained to determine the critical rotational speed of the chamber, particle movement velocity, and the power required for the mixing process. Laboratory experiments showed that the average particle movement velocity was 1.21 m/s and the average friction coefficient was 0.40. Under optimal operating conditions, the mixture uniformity reached 95.7% after 4 min of mixing. The mixer productivity was 0.95 t/h, while the specific energy consumption was 0.5 kWh/t, which is 2.5 times lower than that of conventional mixers equipped with active mixing elements. The obtained results confirm the potential of the proposed gravity-based mixing method for preparing feed and organomineral mixtures in small-scale farming systems.

Abstract: This paper introduces bending anisotropy of gun drill rods, caused by asymmetric cross-section, into chatter stability analysis. A dynamic model considering different stiffnesses along the two principal inertia axes is established. The Galerkin method and semi-discretization method are used to solve the governing equations and generate stability lobe diagrams. Parameter sensitivity analysis shows that drill rod length and material damping coefficient are high-sensitivity parameters, while coolant hole size and eccentric position are low-sensitivity ones. The results reveal the mechanism of bending anisotropy on stability and provide theoretical guidance for chatter suppression in deep-hole machining.

Abstract: This paper investigates how software configuration, hardware type, user background and context of use influence the usability of Virtual Reality (VR) systems in engineering product development. A VR usability assessment approach that combines task-based questionnaires, the System Usability Scale (SUS) and the NASA-TLX questionnaire was evaluated systematically across six experiments involving students, junior engineers and senior engineers in academic and industrial settings. The results demonstrate that user background and task context are at least as signifi-cant as the underlying hardware or software in influencing perceived usability and acceptance. Standalone headsets achieve higher usability scores with inexperienced users, whereas PC-based systems are still necessary for high-precision engineering tasks. Professional engineers primarily evaluate VR in terms of workflow integration, precision and return on investment, whereas students focus more on novelty and the interaction experience. Based on these findings, practical design recommendations have been derived for se-lecting a VR system, adapting interaction concepts, and implementing VR in product development processes. The study highlights that VR should not be deployed as a one-size-fits-all solution, but rather as a tool that is both context-specific and us-er-centered. It also demonstrates how systematic, iterative usability evaluation can directly support the successful industrial integration of VR technologies.

Abstract: As a third-generation semiconductor material, indium phosphide (InP) exhibits complex anisotropic etching characteristics, showing significantly varying etching morphologies under different temperature, concentration, and surfactant conditions. This complexity poses challenges in controlling the etching evolution process and predicting its three-dimensional structures. To address the simulation of InP etching structures and surface morphology, this study first establishes an atomic model of the InP etching system and analyzes how different atomic structures influence crystal plane etching rates. Subsequently, based on the microscopic activation energy theory, we propose an atomic removal determination function (InP-RPF) for InP etching substrates, numerically elucidating the relationship between macroscopic crystal plane etching rates and microscopic atomic removal probabilities. Furthermore, we develop an evolutionary Monte Carlo etching system model (InP-EMC), employing evolutionary algorithms to continuously optimize the energy parameters in the InP-RPF function, thereby adjusting the removal probabilities of various atomic types on the substrate and validating the simulated etching rates. Experimental comparisons demonstrate that the InP-EMC model accurately constrains atomic removal probabilities using limited crystal plane etching rate data, achieving simulation accuracy exceeding 90% for full-crystal-plane etching rates, mask etching structures, and surface morphology characteristics.

Abstract: Imidacloprid (IMI), the commonly used neonicotinoid pesticide, has emerged as a persistent aquatic contaminant due to its high solubility and stability, posing risks to non-target organisms and ecosystem health. In this study, a MnZnFe₂O₄/SrWO₄ ferrite–tungstate nanocomposite was synthesized via a hydrothermal process and its ability to photocatalytically degrade IMI under UV light was assessed. SEM, XRD and FT-IR were used to characterize the composite to confirm its structural and morphological features. Photocatalytic performance was systematically investigated by examining the effects of operational factors, including initial pollutant concentration, catalyst dosage, pH, and irradiation time. The MnZnFe₂O₄/SrWO₄ nanocomposite exhibited significantly enhanced activity, achieving up to 87% degradation of IMI within 30 minutes at pH 9, outperforming individual components (SrWO₄: 37%; MnZnFe₂O₄: 75%) under identical conditions. The degradation kinetics followed a pseudo-first-order model consistent with the Langmuir–Hinshelwood mechanism. Effective interfacial charge transfer between the ferrite and tungstate phases, which promotes electron-hole recombination and increases the production of reactive species, is responsible for the enhanced performance. Furthermore, the composite demonstrated good stability and reusability across several cycles, indicating its practical applicability. Overall, the results demonstrate the potential of MnZnFe₂O₄/SrWO₄ nanocomposites as efficient and sustainable photocatalysts for removing imidacloprid and similar organic contaminants from aqueous systems.

Abstract: Heat removal by spray impingement is widely used in different industrial processes. A cooling regime of particular interest occurs when the temperature of the cooled surface exceeds the Leidenfrost temperature of the spray. An accurate numerical model of this cooling regime could help to optimise many industrial applications where spray cooling is used, such as cryogenic machining and spray quenching. In this paper, an Eulerian-Lagrangian Conjugate Heat Transfer (CHT) model designed for spray impingement above the Leidenfrost temperature is proposed. Two different sub-models are implemented to quantify the heat transfer between the droplet and the solid. The heat transfer models are validated through a literature experimental campaign, showing accurate and flexible prediction of heat transfer characteristics across diverse operating conditions, temperature levels, and spray configurations.

Abstract: In this study, a six-degree dynamic model considering torsion and bending is proposed for a single-stage spur gear reducer. The objective is to study the effect of progressive pitting on the dynamic behavior of the system. The evolution of mesh stiffness over time is modeled using an energy-based approach that takes into account the geometric characteristics of pitting defects, including their depth, width, and location on the gear teeth. The equations of motion are obtained using the Lagrangian method and subsequently solved numerically using the Runge-Kutta scheme. Vibration responses are analyzed in the time, frequency, and time-frequency domains for both healthy and damaged gears. The results show that the onset of pitting leads to a significant loss of stiffness, amplitude modulation, and the appearance of spectral sidebands near the mesh frequency. A quantitative parametric sensitivity analysis reveals that the apparent contact velocity plays a predominant role at low speeds and in the early stages of damage. In contrast, at high speeds and advanced degradation levels, pit depth and width become dominant. The proposed methodology provides valuable comprehension into the propagation mechanisms of pitting faults and offers practical guidance for early failure detection and condition-based maintenance of gear drive systems.

Abstract: In order to enhance the amphibious mobility of robots in water-land environments, this paper proposes a frog-inspired hybrid drive amphibious robot, based on the amphibious locomotion characteristics of frogs. Distinct from existing single-mode frog-inspired jumping or swimming robots, the proposed robot innovatively integrates hybrid propulsion to simultaneously achieve both frog-like swimming and jumping capabilities. On land, the robot utilizes an explosion-driven hind limb actuation mechanism, paired with a linkage-based forelimb posture control system, to achieve high-performance frog-like jumping. In water, a rope-driven hind limb mechanism facilitates extension and retraction movements, while controllable soft-actuated flippers enable swinging and opening/closing motions, thereby achieving efficient frog-like swimming. In addition, an amphibious dynamic model was developed, and the robot's amphibious locomotion capabilities were evaluated and analyzed. Finally, an experimental prototype platform was built to test the amphibious locomotion performance of the designed robot, and a comparative analysis was conducted with the theoretical model. The experimental results not only validated the correctness of the amphibious dynamics and motion theory, but also confirmed the effectiveness of the designed amphibious terrain-crossing mechanism.

Abstract: This study presents an approach to quantifying impact-induced damage severity in composites, focusing on synthetic carbon fibre reinforced polymer (CFRP), natural flax fibre reinforced polymer (FFRP) and hybrid fibres reinforced polymer (HFRP) composite of carbon and flax. The investigation aims to quantitatively characterise impact damage under energies ranging from 10 to 70 J through acousto-ultrasonics (AU) testing, proposing an efficient technique for evaluating the integrity of various FRP composites under in-service conditions. AU testing was performed at azimuthal angles of 0°, 30°, 45°, 60° and 90°, utilising acousto-ultrasonic waveform indices (AUWIs), such as wave velocity, peak amplitude, energy content, centroid frequency and skewness factor. Damage severity index is correlated with the damage mode. The findings establish that wave velocity is a reliable parameter for quantifying damage severity across all composite material types considered, with high adjusted R² values of 0.92 for CFRP, 0.89 for FFRP and 0.90 for HFRP. Peak amplitude also shows considerable sensitivity. Finally, this research highlights the limitations of traditional non-destructive evaluation (NDE) techniques and demonstrates the potential of combining multi-damage metrics with advanced imaging methods, such as X-ray micro-computed tomography (X-ray µCT) and scanning electron microscopy (SEM), to provide comprehensive assessment of damage in various composite materials. The proposed methodology offers a promising approach for quantifying the impact damage severity in composite structures, as applicable to wind turbine blades, amongst other structural components.

Abstract: Soft robotics is a rapidly evolving field that has attracted significant attention within the scientific community. This review analyzes the main advantages of pneumatic technology in service robots across the different application domains defined by the International Federation of Robotics (IFR). By organizing the literature according to application domains, this work aims to clarify the specific benefits of pneumatic and soft pneumatic solutions in each context. The proposed approach distinguishes between traditional pneumatic solutions and the subsequent emergence of soft robotics, in order to highlight how and to what extent soft technologies have reshaped the design and application scenarios. Particular attention is devoted to the role of materials and recent manufacturing techniques used by researchers to fabricate soft pneumatic robots. Finally, current research trends are discussed, with the goal of identifying key directions for the further development of soft pneumatic service robots.

Abstract: Silver nanoparticles (AgNPs) have attracted significant attention due to their remarkable antimicrobial, antibacterial, and catalytic properties, enabling widespread applications in consumer products, biomedical fields, and environmental systems. Conventional chemical and physical synthesis routes, however, often involve toxic reagents and generate hazardous byproducts, raising environmental and health concerns. In response, green synthesis approaches employing biological entities such as plant extracts, bacteria, and fungi have emerged as sustainable and eco-friendly alternatives. These methods utilize natural reducing and stabilizing agents, minimizing toxicity while enhancing biocompatibility. This review comprehensively examines green-mediated synthesis strategies for AgNP-based composites, highlighting their physicochemical properties and functional performance. Additionally, the potential toxicity and environmental implications of AgNPs are critically discussed. Particular emphasis is placed on their applications in environmental remediation, including water purification, pollutant degradation, and antimicrobial treatments. Overall, green-synthesized AgNP composites offer a promising pathway toward sustainable nanotechnology for environmental pollution control.

Abstract: Transmission error (TE) is widely recognized as the primary internal excitation source in geared systems and plays a central role in vibration and noise generation. While micro-geometry modifications such as barreling are typically defined through nominal parame-ter values, the spatial distribution of tooth-level deviations is often neglected in simula-tion-based NVH assessments. In this study, the influence of tooth-by-tooth barreling dis-tribution on TE and its frequency-domain response was investigated using a controlled single gear-pair simulation model. A constant nominal barreling value was maintained across all cases, while only the spatial distribution of deviations was varied. Four repre-sentative patterns were considered: harmonic, phase-shifted harmonic, clustered with an outlier, and random.The results show that different distribution patterns lead to clearly distinguishable TE signals and FFT spectra, despite identical nominal modification levels. Harmonic distributions produce regular, periodic responses with clean spectral signa-tures. In contrast, phase-shifted patterns introduce modulation effects and sideband structures around the gear mesh frequency (GMF). Clustered deviations generate localized peaks and fault-like spectral features, while random distributions result in broader, less structured excitation. These findings indicate that the NVH-relevant effect of microgeome-try cannot be described solely by nominal amplitude. The spatial distribution of tooth-level deviations significantly influences both the temporal structure and spectral content of TE. The study highlights the importance of incorporating distribution-aware approaches in simulation-driven gear NVH analysis.

Abstract: Small unmanned aerial vehicle (UAV) acoustic signatures have become increas-ingly relevant not only from the perspective of environmental noise mitigation, but also for detectability, surveillance vulnerability, and low-observable aerial system design. While most prior studies focus on rotor-noise reduction through high-fidelity computa-tional fluid dynamics (CFD) or experimental testing, comparatively fewer studies ad-dress reduced-order computational frameworks capable of rapidly predicting both acoustic signatures and detection distances under varying operating conditions. This study presents a physics-informed reduced-order computational aeroacoustic framework integrating blade passing frequency harmonic modeling, aeroacoustic scaling laws, atmospheric propagation, and beamforming-informed detectability metrics for rapid prediction of small UAV acoustic signatures. The methodology combines harmonic spectral synthesis, rotational speed scaling, source propagation modeling, and sig-nal-to-noise-based detection criteria to estimate sound pressure spectra, directional acoustic signatures, and acoustic detection distance envelopes. Computational results indicate strong agreement with trends reported in published UAV aeroacoustic ex-periments and suggest that propeller operating speed dominates both acoustic signature growth and detectability range. For representative multirotor conditions, modeled detection distances vary from approximately 80 m to over 200 m depending on rotational speed and ambient noise floor, while reduced source signature scenarios can reduce detectability by up to 30%. The proposed framework provides a computationally efficient tool for rapid aeroacoustic assessment, acoustic signature management, and preliminary low-observable UAV design.

Abstract: The rapid proliferation of unmanned aerial vehicles (UAVs) in urban and peri-urban environments has increased concern regarding drone-generated acoustic emissions, particularly in multirotor platforms whose tonal and broadband noise is strongly influenced by propeller blade geometry. This study presents a CFD-based aeroacoustic assessment framework to examine the influence of key geometric modifications on the acoustic signature of a representative multirotor propeller while preserving aerodynamic performance. A baseline quadrotor propeller was analyzed using Reynolds-Averaged Navier–Stokes (RANS) simulations coupled with the Ffowcs Williams–Hawkings (FW-H) acoustic analogy and Brooks–Pope–Marcolini (BPM) broadband noise estimation. The blade geometry was parameterized in terms of leading-edge sweep, tip chord, blade twist, and trailing-edge serration features, and representative low-noise configurations were evaluated under operating conditions ranging from 3000 to 6000 RPM and advance ratios between 0 and 0.3. The results indicate that combined swept-serrated geometries provide the most favorable noise–performance trade-off, with a predicted reduction of up to 4.8 dB(A) relative to the baseline at the design condition, while maintaining thrust and figure of merit within practical engineering margins. The proposed framework provides a transferable computational basis for the systematic design of low-noise propellers for surveillance UAVs, commercial multirotors, and emerging urban air mobility applications.

Abstract: Small unmanned aerial vehicles (UAVs) are increasingly used in maritime monitoring, coastal inspection, environmental assessment and ISR-oriented research applications. Their operational and scientific value depends not only on endurance, payload capacity and navigation performance, but also on the extent to which acoustic and visual signatures can be measured, compared and managed without compromising aerodynamic efficiency, energy consumption or system reliability. This paper develops a systems engineering framework for acoustic and visual signature management in small multirotor UAVs, derived from a graduate thesis project on UAV modification for maritime-support applications. The proposed framework integrates measurable requirements, acoustic metrics, visual observability indicators, design-variable traceability and staged verification logic. Acoustic assessment is organized around sound pressure level, overall sound pressure level, blade-passing frequency and harmonic content, while visual assessment is structured through luminance contrast, apparent angular size, surface reflectance and background-dependent observability. Rather than presenting operational stealth claims, the study provides a conservative and verifiable methodology for transforming conceptual UAV modification work into reproducible scientific evidence. The contribution of this work is a publication-oriented framework that connects aeroacoustics, CFD-supported modelling, visual observability and multi-domain trade-off analysis within a responsible dual-use research boundary. The framework supports the systematic evaluation of UAV signature-management strategies while preserving academic transparency, technical reproducibility and ethical publication standards.

Abstract: This study presents a framework for developing, emulating, and validating offshore wind turbine models when proprietary blade designs are unavailable. The methodology addresses a critical industry challenge by demonstrating that accurate aero-servo-hydro-elastic models can be constructed using only publicly available reference designs and operational measurements. An inverse design approach based on differential evolution optimization reconstructs blade aerodynamic characteristics from field data, enabling the creation of models that replicate operational behavior without requiring access to proprietary geometries. The framework incorporates comprehensive uncertainty quantification through machine learning techniques to predict simulation errors based on environmental and operational conditions. Validation against extensive field measurements from an operational offshore wind turbine demonstrates the effectiveness of the methodology. This approach offers a practical pathway for model calibration and error prediction for offshore wind turbines, particularly when complete design documentation is unavailable.

Abstract: Based on outer raceway control theory and considering the effects of elastic deformation, centrifugal force, and gyroscopic moment between the rolling elements and raceways, a geometric and force analysis of angular contact ball bearings is conducted. A five-degree-of-freedom theoretical model capable of accounting for the combined action of radial force and moment is established. The accuracy of the model is verified through numerical calculations and experimental results from existing literature. Upon validation of the theoretical model, a modified Archard model is employed to develop a wear volume model for the bearing raceways. The influence of both single and combined loads on sliding wear in the bearing raceways is systematically analyzed.

Abstract: The vibroacoustic simulation of geared drivetrains has become increasingly important as electrified powertrains expose tonal gear noise and high-frequency structure-borne excitation more clearly than conventional internal-combustion vehicles. In this context, software choice is no longer a secondary implementation detail but a central engineering decision, because different platforms emphasize different parts of the excitation–transfer–radiation chain. This review therefore examines gearbox and geared-drivetrain NVH simulation from a software-specific perspective rather than a purely phenomenon-based one. The article critically compares dedicated gearbox CAE tools, general multibody dynamics platforms, integrated multiphysics and structural–acoustic finite-element environments, and early-stage 1D system simulation tools. The comparison covers major software ecosystems including KISSsoft/KISSsys, Romax Suite, SMT MASTA/DRIVA, MSC Adams, AVL EXCITE, RecurDyn/DriveTrain, Siemens Simcenter 3D Motion / Transmission Builder / Acoustics, SIMULIA Simpack, Ansys Motion with Mechanical/Acoustics and Motor-CAD, COMSOL Multiphysics, GT-SUITE, and Simcenter Amesim, while also considering relevant recent module extensions and workflow updates. The review shows that the current software landscape is structured around four main methodological layers: dedicated gearbox analysis tools that are strongest in gear-contact modeling and microgeometry iteration; high-fidelity multibody platforms that are strongest in system-level dynamic response and transmission-path representation; integrated structural–acoustic environments that provide the deepest access to housing vibration and radiated-noise prediction; and 1D or multidomain system tools that are most efficient for early concept evaluation and architecture-level trade-off studies. Recent developments since 2023 indicate a clear shift toward tighter support for electrified drivetrain NVH, measured manufacturing deviations, optimization workflows, and faster acoustic prediction, including reduced-order or embedded acoustic methods. At the same time, major gaps remain. Open literature still contains relatively few independent studies that validate the full chain from tooth contact and transmission error through dynamic transfer paths to housing vibration and radiated sound within a single commercial workflow. Likewise, interoperability for measured flank topography, wear-driven NVH evolution, and fully validated electro-magnetic–mechanical–acoustic simulation remains limited and uneven across platforms. For this reason, the review argues that current software ecosystems are best understood not as universally proven end-to-end solutions, but as partially overlapping toolchains with different strengths, evidence levels, and practical compromises.

Abstract: Metal binder jetting (MBJ) is an additive manufacturing (AM) process that offers advantages such as high speed, low cost, and low residual stress, compared to the prevalent fusion-based metal AM methods. However, a major barrier to MBJ is the low density of manufactured parts, which restricts part quality and limits its applications. One key process parameter that affects part density is the packing density of the powder bed. In general, a higher packing density is preferable in MBJ. Although research has been conducted to enhance the packing density ex-situ, most proposed approaches lack robustness when applied to real-world printing, where environmental variations and stochastic powder behavior introduce inconsistencies. An in-situ sensing method for packing density can mitigate these issues in several ways. It enables the implementation of feedback control strategies to regulate packing density during printing, contributes to comprehensive in-situ process monitoring, and provides quantitative data to support post-processing analysis and optimization. However, effective in-situ methods for accurately sensing packing density remain limited. To fill this research gap, two methods, namely ultrasound (acoustic) and recoating-force sensing, are proposed as potential approaches for in-situ sensing of powder packing density. Using a dedicated test platform, their responses to different powder bed packing densities are measured and compared. The results show a strong correlation between packing density and the sensor measurements, with differing levels of estimation confidence, demonstrating promising potential for their implementation as in-situ packing density sensors. Furthermore, the concept of sensor fusion is tested by combining the force-sensing and acoustic-sensing data, leading to improvements in the estimation confidence.

Abstract: This study presents a hybrid additive manufacturing approach to fabricate bioinspired stainless steel 316L-copper (SS316L-Cu) multimaterial structures using laser powder bed fusion (LPBF). The present study incorporates honeycomb lattice structures with varying wall thicknesses (0.25 mm, 0.5 mm, 0.75 mm, and 1.0 mm) to investigate the effect of geometric parameters on mechanical performance. Mechanical testing was conducted according to ISO 6892 standards, and the results revealed a strong dependence of tensile strength and ductility on lattice thickness. Copper (Cu) infiltration into SS316L lattice structures improved ductility by 30% compared to the monolithic SS316L lattice, with minimal compromise in tensile strength. To complement experimental results, molecular dynamics (MD) simulations were performed to study atomic-scale deformation and validate the trend of strength enhancement with increasing wall thickness. The findings demonstrate the potential of combining LPBF and liquid Cu infiltration to develop multifunctional, mechanically robust, and thermally conductive metallic composites. This approach provides valuable insight into structure–property relationships and supports the design of next-generation multifunctional composites for structural and thermal applications.