Search Results (180)

This paper presents the results of a numerical study on the influence of the tooth root fillet manufacturing method on the bending strength of spur gears with straight teeth. A mathematical model describing the gear tooth geometry was developed, in which the transition curve at the tooth root was directly related to the applied machining process—either rack-type gear shaping or pinion-type gear shaping. Based on this model, a numerical procedure for calculating the bending stresses at the tooth root was formulated and verified using the finite element method (FEM). The results demonstrated high consistency between the proposed approach and FEM analysis, confirming the accuracy of the developed mathematical model and numerical methodology. The study also examined the effect of the tool fillet radius on the stress distribution in the root region. It was found that increasing the tool radius leads to a reduction in bending stresses, while the differences between the two machining methods gradually diminish. The proposed methodology offers a reliable numerical framework for assessing the strength of spur gears and can be effectively used in the design of lightweight, high-performance gear transmissions for aerospace and automotive applications. Full article

This study addressed the issue of insufficient lubrication in the thrust washer of the planetary gear reducer during operation. Numerical simulations were performed under fixed operating conditions, combined with sequential optimization strategy, to systematically investigate the influence of V-shaped texture distribution and geometric parameters on lubrication characteristics during unidirectional rotation. The results revealed that, under the examined texture parameters, the oil film pressure increased significantly with increasing radial velocity from inner to outer radius and lubricant viscosity, with area density being the key parameter influencing load-carrying capacity. Moreover, selectively enhancing the texture density in the outer ring region effectively alleviated wear caused by stress concentration in that area. The optimal V-shaped texture parameters were determined as follows: a length ratio of 5, an angle of 30°, an area density of 24.52%, and a depth of 0.02 mm. The symmetry axis of the texture was oriented opposite to the fluid velocity, and the texture distribution exhibited radial densification. This study will inform the design of surface textures and enhance the lubrication performance of mechanical components in thrust washers and similar rotational operating conditions. Full article

Knee flexion refers to the relative motion between the tibia and femur including rolling and sliding (rollback motion). Notwithstanding the individual variations in knee motion, conventional wearable knee-assistive devices use hinge joints—resulting in nonnegligible mismatched movements, particularly during deep flexion. Therefore, we proposed a biomimetic knee joint (BKJ) that adapts to individual knee motion. A polycentric BKJ, integrating two gears with different radii, was designed to match the trajectory of the rotational axes of the knee. In this study, we developed a semi-active polycentric BKJ (SA-BKJ) incorporating an adjustable reaction-force mechanism (ARFM). In the ARFM, the combined spring constant can be adjusted using a shape-memory alloy actuator owing to its compact size, lightweight nature, and low energy consumption. In addition, the geared joint of the SA-BKJ (which integrates two gears with different radii) was designed to match the average trajectory of the rotational axes of the knee (of 22 healthy men). Applying the genetic algorithm, the radius of the femur and tibia gears were determined to be 25.5 and 40.0 mm. Misalignments of the designed SA-BKJ were measured in three healthy male participants. The error measurements averaged 20 degrees in the control device and 10 degrees in the optimized device. These results indicated that the optimized gears of the SA-BKJ totally reduced the misalignment. Full article

Quiet drivetrains have become a central requirement in modern electric vehicles, where the absence of engine masking makes even subtle gear tones clearly audible. As a result, manufacturers are looking for more reliable ways to understand how design choices, manufacturing variability, and operating conditions shape gear noise and vibration. Digital Twin (DT) approaches—linking high-fidelity models with measured data throughout the product lifecycle—offer a potential route to achieve this, but their use in gear NVH is still emerging. This review examines recent work from the past decade on DT concepts applied to gears and drivetrain NVH, drawing together advances in simulation, metrology, sensing, and data exchange standards. The survey shows that several building blocks of an NVH-oriented twin already exist, yet they are rarely combined into an end-to-end workflow. Clear gaps remain. Current models still struggle with high-frequency behavior. Real-time operation is also limited. Manufacturing and test data are often disconnected from simulations. Validation practices lack consistent NVH metrics. Hybrid and surrogate modeling methods are used only to a limited extent. The sustainability benefits of reducing prototypes are rarely quantified. These gaps define the research directions needed to make DTs a practical tool for future gear NVH development. A research Gap Map is presented, categorizing these gaps and their impact. For each gap, we propose actionable future directions—from multiscale “hybrid twins” that merge test data with simulations, to benchmark datasets and standards for DT NVH validation. Closing these gaps will enable more reliable gear DTs that reduce development costs, improve acoustic quality, and support sustainable, data-driven NVH optimization. Full article

Object detection plays a crucial role in remote sensing and UAV image technology, but it faces the challenge of speed and accuracy in multi-scale dense small target mission detection scenarios and is susceptible to noise interference, such as weather conditions, lighting changes, and occluded backgrounds in complex backgrounds. In recent years, Mamba-based methods have become hot in the field of object detection, showing great potential in capturing remote dependencies with linear complexity but lacking deep customization of remote sensing targets. Based on this, we propose GMG-LDefmamba-YOLO, which contains two core modules: the Gaussian mask gear convolution module forms a gear-shaped receptive field through improved convolutional splicing to enhance the extraction of small target features and combines the Gaussian mask mechanism to dynamically modulate the feature weights to suppress complex background interference. The linear deformable Mamba module integrates linear deformable sampling, a spatial state dual model, and residual gating MLP components, integrating the advantages of flexible capture of local features and efficient modeling of global dependence, dynamically adapting to target scale changes and spatial distribution, and reducing computational costs. Experiments on DOTA-v1.0, VEDAI, and USOD datasets show that the mAP50 of the model reaches 70.91%, 77.94%, and 90.28%, respectively, which is better than the baseline and mainstream methods, and maintains the lightweight characteristics, providing efficient technical support for remote sensing monitoring, UAV inspection, and other fields. Full article

In comparison to internal combustion engines, which usually have low frequency, broadband excitations, in electric vehicles, tonal excitations from the electric drivetrain are noticeable and disturbing. As the acoustic and structural dynamic behavior, often referred to as noise, vibration, and harshness (NVH), strongly influences customers’ quality perceptions, optimizing it is a key challenge in development. This study investigates the influence of static rotor–stator eccentricity on the NVH behavior of an electric drivetrain using a transient elastic multibody simulation (eMBS) model incorporating non-linear gear meshing, bearing contact, and electromagnetic forces. The analysis identifies the 36th order excitation of the electric machine as the dominant source, leading to a maximum total acceleration level of 152 dB. Two specific excitation directions were found to reduce this amplitude most effectively. However, varying the amount of static eccentricity in these directions resulted in only minor vibration reductions (<1.5 dB). The findings indicate that the symmetric mode shapes of the cylindrical housing govern the response, indicating that addressing the excitability of housing modes by developing asymmetric housing designs could offer a more effective approach for NVH optimizations of electric drivetrains. Full article

Biomimetic knee exoskeletons often struggle to balance accurate replication of joint biomechanics with efficient torque transmission. This study presents a knee exoskeleton featuring a single-stage planetary gear set with three coupled interface gears to reproduce the coupled rolling–sliding motion of the human knee. By mapping rolling and sliding displacements into distinct gear-driven motions, the design achieves a near-linear relationship approximating the physiological J-shaped instantaneous center of rotation (ICR). Gear parameters were optimized under biomechanical and engineering constraints, producing a compact, manufacturable configuration with ICR deviation ≤ 5 mm (sliding distance). Performance experience demonstrates that the optimized joint reduced sliding misalignment of the contact point by 73.4%, delivered peak output torque in agreement with predictions, and maintained an average efficiency of 95.4% across operating speeds. These findings confirm that the proposed mechanism enhances kinematic fidelity and actuation performance, offering a promising solution for next-generation rehabilitation exoskeletons. Full article

The gear transmission system is a safety-critical component in rail transit, typically designed for a service life exceeding 20 years. Failure analysis of such systems remains a key focus for railway engineers. This study systematically investigates four representative cases of premature gear failure in high-speed trains using a standardized analytical procedure that includes visual inspection, chemical analysis, metallographic examination, scanning electron microscopy, and hardness testing. The results identify four primary root causes: subsurface slag inclusions in raw materials, inadequate heat treatment leading to a non-martensitic layer (∼60 μm) at the tooth root, grinding-induced temper burns (crescent-shaped "black spots") accompanied by a hardness drop of ∼100–150 HV, and insufficient lubrication. The interdependencies between these factors and failure mechanisms, e.g., fatigue cracking, spalling, and thermal scuffing, are analyzed. This work provides an evidence-based framework for improving gear reliability and proposes targeted countermeasures, such as ultrasonic inclusion screening and real-time grinding temperature control, to extend operational lifespans. Full article

Education is pivotal in shaping a future geared toward climate neutrality and cultivating agents of change capable of addressing sustainability challenges. Educators’ understanding of food sustainability influences how effectively it is integrated into educational programs. This study examined the knowledge and understanding of food sustainability among nutrition and agri-food educators in Europe as part of a joint European-funded project (2023-1-IE01-KA220-VET-00156916: Train to Sustain). After ethical approval, a survey was distributed to educators in Ireland, Slovenia, Poland, and Italy. Data were analysed using qualitative and quantitative methods. Of the 123 educators who participated, 81% agreed they fully understood “food sustainability,” and 97% believed it is important to include it in education, yet only 62% reported that it was currently taught in their programs. This reveals a gap between perceived importance and implementation. The data also offered insights into how educators understand food sustainability across environmental, economic, social, cultural, and food security dimensions and how these are incorporated into teaching and awareness raising. Three themes were identified: (1) understanding sustainable food systems, (2) sustainable resource management, and (3) educating for food security and resilience. Participants emphasised environmentally friendly food practices, often linked to zero waste goals. The qualitative findings underscored the importance of societal access to healthy food, focusing on food security. However, references to economic and cultural aspects of sustainability were limited, suggesting a potential gap in educators’ understanding. This study highlights the need for educators to possess comprehensive knowledge of food sustainability to advance education and address climate and sustainability challenges. Full article

This work presents a novel wireless charging system for unmanned aerial vehicles (UAVs), which employs conical-shaped coils that also function as landing gear. By integrating electromagnetic simulation, circuit modeling, and system-level evaluation, we introduce an innovative coil design that enhances wireless power transfer (WPT) efficiency while reducing misalignment sensitivity. The conical geometry naturally facilitates mechanical alignment upon drone landing, thereby improving inductive coupling. High-frequency simulations were carried out to optimize the coil parameters and evaluate the link efficiency at 6.78 MHz, an ISM-designated frequency. Our experimental testing confirmed that the proposed conical coil achieves high power transfer efficiency (up to 94%) under practical conditions, validating the effectiveness of the geometry. The characteristics of the designed coil make it highly suitable for use with Class EF amplifiers operating in the same frequency range; however, detailed amplifier hardware implementation and efficiency characterization were beyond the scope of this study and are reserved for future work. The results demonstrate the potential of the proposed system for deployment in UAV field applications such as surveillance, delivery, and remote sensing. Full article

To extend the time between the overhauls of helicopters, a novel collaborative methodology that takes into account uncertain misalignment errors by considering the shape and performance of the gear is built. Firstly, the digital characteristics of contact patterns, such as the reference point and direction angle, are extracted. Secondly, an optimization model calculates the equivalent misalignment by minimizing deviations in the reference point and direction angle between two contact patterns. This equivalent misalignment accounts for uncertainty misalignment errors introduced by complex gear support deformation. Thirdly, the ease-off is utilized to derive the pinion target surface that can sustain meshing performance under an equivalent misalignment, similar to the original gear in real conditions. This way it integrates with the optimization theory for flank reconstruction to redesign the pinion surface. Simulations reveal that the critical digital characteristics of the contact path on the original gear under the equivalent misalignment mirror those of the original gear in real conditions. Moreover, the surface parameters of the redesigned pinion result in an identical surface under a different equivalent misalignment, maintaining similar contact and dynamic performance. This proposed collaborative design approach, considering the shape and performance while accounting for uncertain misalignment errors through ease-off, greatly improves the gear transmission behavior. Full article

In response to the growing demand for lightweight and high-efficiency industrial equipment, this study addresses the critical issue of lubrication failure in high-speed, heavy-duty gear reducers, which often leads to reduced transmission efficiency and premature mechanical damage. A three-dimensional transient multiphysics-coupled model of oil-jet lubrication is developed based on computational fluid dynamics (CFD). The model integrates the Volume of Fluid (VOF) multiphase flow method with the shear stress transport (SST) k−ω turbulence model. This framework enables the accurate capture of oil-jet interface fragmentation, reattachment, and turbulence-coupled behavior within the gear meshing region. A parametric study is conducted on oil injection velocities ranging from 20 to 50 m/s to elucidate the coupling mechanisms between geometric configuration and flow dynamics, as well as their impacts on oil film evolution, energy dissipation, and thermal management. The results reveal that the proposed method can reveal the dynamic evolution characteristics of the gear injection lubrication. Adopting an appropriately moderate injection velocity (30 m/s) improves oil film coverage and continuity, with the lubricant transitioning from discrete droplets to a dense wedge-shaped film within the meshing zone. Optimal lubrication performance is achieved at this velocity, where oil shear-carrying capacity and kinetic energy utilization efficiency are maximized, while excessive turbulent kinetic energy dissipation is effectively suppressed. Dynamic monitoring data at point P further corroborate that a well-tuned injection velocity stabilizes lubricant-velocity fluctuations and improves lubricant oil distribution, thereby promoting consistent oil film formation and more efficient heat transfer. The proposed closed-loop collaborative framework—comprising model initialization, numerical solution, and post-processing—together with the introduced quantitative evaluation metrics, provides a solid theoretical foundation and engineering reference for structural optimization, energy control, and thermal reliability design of gearbox lubrication systems. This work offers important insights into precision lubrication of high-speed transmissions and contributes to the sustainable, green development of industrial machinery. Full article

Under the trend of lightweight and high-efficiency development in industrial equipment, precise regulation of lubrication in gear reducers is a key breakthrough for enhancing transmission system efficiency and reliability. This study establishes a three-dimensional numerical model for high-speed gear jet lubrication using computational fluid dynamics (CFD) and dynamic mesh technology. By implementing the volume of fluid (VOF) multiphase flow model and the standard k-ω turbulence model, the study simulates the dynamic distribution of lubricant in gear meshing zones and analyzes critical parameters such as the oil volume fraction, eddy viscosity, and turbulent kinetic energy. The results show that reducing the oil injection distance significantly enhances lubricant coverage and continuity: as the injection distance increases from 4.8 mm to 24 mm, the lubricant shifts from discrete droplets to a dense wedge-shaped film, mitigating lubrication failure risks from secondary atomization and energy loss. The optimized injection distance also improves the spatial stability of eddy viscosity and suppresses excessive dissipation of turbulent kinetic energy, enhancing both the shear-load capacity and thermal management. Dynamic data from monitoring point P show that reducing the injection distance stabilizes lubricant velocity and promotes more consistent oil film formation and heat transfer. Through multiphysics simulations and parametric analysis, this study elucidates the interaction between geometric parameters and hydrodynamic behaviors in jet lubrication systems. The findings provide quantitative evaluation methods for structural optimization and energy control in gear lubrication systems, offering theoretical insights for thermal management and reliability enhancement in high-speed transmission. These results contribute to the lightweight design and sustainable development of industrial equipment. Full article

Gear whine noise is governed not only by intentional microgeometry modifications but also by unavoidable pitch (indexing) deviation. This study presents a workflow that couples a tooth-resolved surface scan with a calibrated pitch-deviation table, both imported into a multibody dynamics (MBD) model built in MSC Adams View. Three operating scenarios were evaluated—ideal geometry, measured microgeometry without pitch error, and measured microgeometry with pitch error—at a nominal speed of 1000 r min⁻¹. Time domain analysis shows that integrating the pitch table increases the mean transmission error (TE) by almost an order of magnitude and introduces a distinct 16.66 Hz shaft order tone. When the measured tooth topologies are added, peak-to-peak TE nearly doubles, revealing a non-linear interaction between spacing deviation and local flank shape. Frequency domain results reproduce the expected mesh-frequency side bands, validating the mapping of the pitch table into the solver. The combined method therefore provides a more faithful digital twin for predicting tonal noise and demonstrates why indexing tolerances must be considered alongside profile relief during gear design optimization. Full article

This study presents a computational fluid dynamics (CFDs) investigation of the hydrodynamic behavior of surface-textured lateral bushings in external gear pumps (EGPs), emphasizing the effects of combined sliding and squeezing motions within the lubrication gap. A comprehensive numerical model was developed to analyze how surface texturing implemented through different dimple shapes and texture densities influences pressure distribution and load-carrying capacity under transient lubrication conditions. The analysis demonstrates that the interaction between shear-driven flow and squeeze-film compression significantly amplifies pressure, particularly when optimal dimple configurations are applied. Results indicate that dimple geometry, depth, and arrangement critically influence hydrodynamic performance, while excessive texturing reduces effectiveness due to increased average gap height. Cavitation was intentionally not modeled in the early single dimple evaluations to allow clear comparison between configurations. The findings offer a design guideline for employing surface textures to enhance tribological performance and efficiency in EGP applications under realistic dynamic conditions. Full article