Search Results (97)

A multiscale contact model is developed for micro-textured gear interfaces incorporating Micro-Convex-Concave Asperity (MCCA) characteristics to elucidate the synergistic modulation between Interface Enriched Lubrication (IEL) performance and Anti-Scuffing Load-Bearing Capacity (ASLBC) of Micro-Textured Meshing Interfaces (MTMI) under transient Thermal Elastohydrodynamic Lubrication (TEHL) conditions. Homogenization theory is employed to quantify the effects of areal density and depth-to-diameter ratio on IEL characteristics. A time-resolved micro-elastohydrodynamic lubrication model, formulated through dimensionless discretization and adaptive mesh refinement, investigates the influences of autocorrelation length and MCCA amplitude on interfacial behavior. A correlation framework linking Micro-Element Texture (MET) geometric parameters to meshing ASLBC is established to identify optimal textures for simultaneous enhancement of IEL and ASLBC. Experimental observations demonstrate qualitative consistency with numerical predictions regarding the evolutionary trends of temperature fields and dynamic friction coefficients, providing preliminary physical validation for the proposed model. Univariate Sensitivity Analysis (USA) and Multiple Linear Regression (MLR) are further utilized to optimize microtexture parameters by elucidating the influences of MET sizes, area ratio, and configuration on meshing ASLBC and friction coefficients. Full article

Planetary gear systems offer compact design and high-power density, but they are strongly influenced by transmission error (TE), which originates from geometric deviations and elastic deflections. This study presents a dynamic model that integrates elastic compliance, mesh stiffness, damping, and error excitation to evaluate coupled gear responses. Numerical results show that planet–ring contacts undergo larger forces and deflections than sun–planet meshes. Time–frequency analysis with continuous wavelet transform (CWT) reveals nonstationary vibration patterns, while gear tooth flank inspection confirms torque bias and micro-pitting. The findings connect modeling predictions with observed wear, offering insights for planetary gear diagnostics and design. Full article

In the ElastoHydrodynamic Lubrication (EHL) meshing contact model for rough interfaces with convex–concave textured micro-asperities, the geometric morphology of the meshing interface exhibits pronounced multiscale characteristics: the macroscale manifests as the correlation between Interface-Enriched Lubrication (IEL) performance and meshing Anti-Scuffing Load-Bearing Capacity (ASLBC), while the microscale corresponds to the textured morphology of rough interfaces. In numerical simulations of EHL meshing contact, such cross-scale disparities necessitate solving large-scale systems of analytical solution equations. Assuming periodicity or quasi-periodicity at the microscale, various established methods enable decoupling the macroscopic and microscopic scales, such formalized approaches constitute homogenization theory. However, classical asymptotic assumptions may introduce considerable approximation errors. This study proposes a micro-texture-informed homogenized contact model based on multiscale characterization that incorporates the coupled effects of gear interface meshing forces and thermo-elastic deformations, effectively extending the applicability of classical asymptotic homogenization methods. Full article

With the changing demands of society, gears, as fundamental components of mechanical devices, are evolving towards higher reliability and longer service life. To address the issue of thermal scuffing at the gear meshing interface, we propose the introduction of micro/nano-textures to improve the thermal elastohydrodynamic lubrication characteristics of the meshing surfaces, thereby enhancing the lubrication performance and anti-scuffing load capacity of the gear surfaces. First, finite element models with different microstructural features were established. Then, numerical calculations were conducted using computational fluid dynamics (CFD) software to analyze the impact of various micro-texture configurations on the lubrication performance of the tooth surface. Finally, an orthogonal experiment was performed to optimize the groove length, groove width, and areal density of the micro-textures in order to obtain the best processing parameters. The results show that, compared with the triangular, rectangular and trapezoidal micro-textures, the wedge-shaped micro-texture produces the largest pressure difference at the meshing-in and meshing-out points of the texture grooves, which causes the dynamic pressure effect to be more obvious. Compared with the triangular, rectangular and trapezoidal micro-textures, the wedge-shaped micro-texture has the largest bearing capacity and the smallest friction coefficient, so it has better bearing capacity and anti-friction and wear performance. The process parameters were optimized through orthogonal experiments, and the optimal combination of process parameters was obtained as the areal density of 50%, the depth of micro-pits of 12 µm, and the width of micro-pits of 200 µm. Under these optimal parameters, the pressure difference at the meshing-in and meshing-out points of the wedge micro-texture increased significantly by 255.6% compared to the initial model, and the oil film friction coefficient decreased by 17.857% relative to the initial model. These results demonstrate that the micro-texture with optimal parameters significantly enhances the lubrication and anti-friction/wear performance of the tooth surface. Full article

To reduce the time and computational cost of vibro-acoustic simulations in gear reducer noise evaluation, this study develops a simulation-driven surrogate modeling framework for a three-stage helical gear reducer. A high-fidelity “vibration–acoustic radiation” simulation chain is established, where the housing vibration responses computed in Romax Designer are mapped into ACTRAN to obtain the radiated noise. Using Optimal Latin Hypercube Sampling, 300 designs are generated by varying the first-stage pinion micro-modification parameters (tooth drum, tooth slope, and tooth profile), and the average RMS sound pressure level over six field points is adopted as the noise metric. A BP neural network (BPNN) surrogate is then constructed, in which Bayesian Optimization (BOA) is used to tune hidden layer nodes and learning rate, and an improved Sparrow Search Algorithm (ISSA) is employed to optimize the initial weights and biases, forming the proposed BOA-ISSA-BPNN model. On the test set, the proposed model achieves R² = 0.97499, RMSE = 0.91385, and MAE = 0.6547, with an average prediction time of 32.35s. Meanwhile, comparisons with SVM, BPNN, BOA-BPNN, SSA-BPNN, and ISSA-BPNN demonstrate superior prediction accuracy; moreover, relative to the hour-level computational cost of high-fidelity simulations, the proposed surrogate enables rapid noise evaluation on the order of tens of seconds, enabling fast micro-modification design iteration and practical engineering decision-making. Full article

The fatigue pitting model based on the minimum oil film thickness does not consider the influence of tooth surface roughness and residual stress, which limits the accuracy of predicting the fatigue pitting of the model. Micro pitting often initiates on the surface due to large external loads. Therefore, it is urgent to propose a new-micro pitting bearing capacity model based on gear surface integrity parameters. This paper studied a new fatigue pitting model considering surface integrity subjected to polishing processes. This model thoroughly analyzes the effects of teeth surface roughness dynamically on the oil film pressure and explores the complex mechanism of residual stress in the near-surface stress field of the gear teeth. The new model can more accurately simulate the micro-pitting bearing capacity under actual operating conditions by introducing teeth surface roughness and residual stress, and the prediction reliability of gear steel is greatly improved. This improved model provides a solid theoretical basis and technical support for optimizing gear transmission systems, accurate diagnosis of micro-pitting defects, and in-depth theoretical research in related fields. Full article

Deep-sea gear transmission systems encounter critical lubrication challenges arising from the synergistic coupling of extreme hydrostatic pressure and cryogenic temperatures. These environmental stressors induce exponential viscosity escalation in lubricants, precipitating severe fluidity degradation, elevated startup resistance, and lubrication starvation. Concurrently, seawater intrusion triggers lubricant emulsification, additive deactivation, and electrochemical corrosion at meshing interfaces, collectively escalating the risk of catastrophic lubrication failure and compromising long-term operational reliability. This study systematically elucidates the lubrication degradation mechanisms inherent to deep-sea environments and proposes targeted mitigation strategies. Through comprehensive characterization of deep-sea environmental parameters and their impact on lubricant rheological behavior, we critically evaluate the applicability and inherent limitations of conventional Thermal Elasto-Hydrodynamic Lubrication (TEHL) theory under extreme conditions. Our analysis reveals that established TEHL frameworks necessitate substantial modification to accurately capture pressure-viscosity-temperature coupling phenomena and seawater contamination kinetics. Meshing interface texturing, as an effective anti-friction and wear-mitigation strategy, is investigated to delineate its mechanistic pathways for enhancing lubricant film formation and tribological performance under starved lubrication regimes. Key findings demonstrate that optimized micro-texture architectures can effectively compensate for viscosity-induced fluidity deficits and attenuate the deleterious effects of seawater ingress. Critical knowledge gaps are identified, and future research trajectories are charted: (i) multiphysics coupling models integrating thermo-hydrodynamic, chemo-physical, and mechanical degradation processes; (ii) synergistic texture-coating design paradigms; (iii) high-pressure low-temperature experimental validation protocols; and (iv) engineering implementation frameworks for deep-sea gear transmission systems. This review establishes theoretical foundations and provides technical guidelines for robust lubrication design and long-term operational stability of deep-sea transmission equipment. Full article

Current research lacks systematic understanding of cross-scale correlations between micro-texture geometry and macro-lubrication behavior. This study presents a multi-scale collaborative optimization methodology for gear Micro-Textured Meshing Interface (MTMI). An objective function targeting macroscopic interfacial performance is formulated, and a topology optimization strategy is employed to achieve optimal MET configuration. The homogenization analysis captures the modulating effects of MET on local flow and stress fields, while topology optimization transcends conventional parametric geometric constraints, enabling the generation of non-regular MET topological patterns tailored to complex operating conditions, thereby ensuring optimal macroscopic ASLBC. The proposed scheme is validated through numerical simulations of two representative problems capturing distinct lubrication regimes: (1) IEL, characterizing transient load-bearing dynamics governed by temporally evolving MET configurations; and (2) ASLBC, elucidating steady-state load-bearing capacity modulation via spatially heterogeneous MET distributions. A Taylor expansion-based surrogate model is developed to efficiently explore the MET configuration design space, significantly enhancing computational efficiency and solution accuracy for multi-scale optimization. While the gradient-based algorithm cannot guarantee global optimality, extensive numerical simulations and cross-validation studies demonstrate consistent convergence toward high-performance MET configurations, with sensitivity analyses of design parameters further confirming the engineering applicability of the optimized solutions. Full article

The gears of helicopter transmission system have strict requirements on machining accuracy, and the accurate prediction of tooth surface grinding force is the key to its manufacturing. The existing model simplifies the micro-contact behavior of the abrasive-workpiece, which limits the accuracy of the grinding load solution. In this paper, the stress state of single abrasive grain at different stages is refined from the micro level, and the grinding force mechanism model of contact area superposition is established. A mechanism-constrained data-driven grinding force prediction algorithm (MCDDP) is proposed. The algorithm integrates the microscopic force mechanism as a physical constraint into the neural network. The experimental results show that the R² of the model for predicting the normal and tangential grinding forces under multiple working conditions is higher than 0.98, and the average error is reduced by about 17% compared with the traditional model. This study reveals the non-uniform force mechanism of abrasive-workpiece, realizes the integration of mechanism model and data-driven method, and provides engineering theoretical and technical support for grinding force prediction and process parameter optimization of aviation precision gears. Full article

As the primary power transmission conduits, aircraft hydraulic pipelines are critical for actuating flight control surfaces and landing gear systems. Accurate in situ strain evaluation of these pipelines is essential, as installation-induced pre-loads directly compromise fatigue life and sealing performance, threatening overall system reliability. However, such evaluation is frequently hindered by the perspective distortions and limited depth of field inherent in conventional imaging systems. To overcome these metrological limitations, this study presents a novel virtual telecentric camera array system designed for high-precision, non-contact strain measurement. Unlike traditional pinhole models, the proposed system leverages a catadioptric setup with planar mirrors to create a virtual four-eye telecentric array from a single physical lens, ensuring constant magnification within the depth of field. A comprehensive simulation framework was established to rigorously compare the reprojection errors and scale accuracies between telecentric and pinhole projection models, quantitatively demonstrating the superior stability of the telecentric approach. Furthermore, a dedicated calibration strategy for non-overlapping telecentric fields of view was developed and validated. Experimental results from pipeline installation tests indicate a high concordance with strain gauge data, confirming that the proposed telecentric system effectively mitigates parallax errors and provides a robust solution for static and quasi-static micro-scale deformation monitoring in complex assembly environments. Full article

The increasing presence of abandoned, lost, or discarded fishing gear (ALDFG) on the seafloor is a major source of microplastics (MPs) pollution in coastal ecosystems. This study assessed the concentration, morphology, and chemical composition of MPs in surface sediments collected from Alicante and Benidorm, in the Valencian Community, eastern coast of Spain, Mediterranean Sea. Impacted sites with fishing nets were compared to control sites without nets. Two analytical techniques were used for polymer identification, depending on particle size: micro-Fourier Transform Infrared Spectroscopy (µFTIR) and Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (FTIR-ATR). The results showed significantly higher MPs concentrations in sites affected by ALDFG. The findings highlight a clear link between the presence of fishing nets and MPs accumulation in sediments. This underlines the urgent need for mitigation strategies and recovery of discarded fishing gear. This study addresses a gap in the literature regarding MPs contamination on rocky coastal substrates and calls for further research to assess the long-term ecotoxicological impacts on marine ecosystems. Full article

Bark is a multifunctional organ critical for tree survival, yet its functional plasticity in response to micro-environmental heterogeneity at alpine timberlines remains poorly understood. Here, we investigated the variations in bark physical traits (thickness, density), allometric scaling, and stoichiometric characteristics (C, N, P) of Abies georgei var. smithii (Viguie & Gaussen) W. C. Cheng & L. K. Fu on contrasting sunny and shady slopes in the Sygera Mountains, southeastern Tibetan Plateau. Despite the relative homogeneity of soil physicochemical properties between slope aspects, bark traits exhibited remarkable phenotypic plasticity. Trees on the shady slope possessed significantly thicker bark with higher nitrogen concentrations, adopting a “resource-acquisitive strategy”. Standardized Major Axis (SMA) regression indicated isometric scaling ($b\approx 1.03$) for trees on the shady slope, reflecting a sustained investment in bark thickness to provide thermal insulation against cold stress. Conversely, trees on the sunny slope exhibited negative allometry ($b \approx 0.87$), characterized by denser tissues and elevated C/N ratios. This shift represents a conservative strategy geared toward hydraulic safety and resistance to high radiation and evaporative loss. Crucially, our results show that bark traits are largely decoupled from soil nutrient gradients, being shaped instead by microclimate. The distinct trade-off—prioritizing insulation on shady slopes versus conservation on sunny slopes—underscores the importance of phenotypic plasticity for the persistence of timberline species in a changing climate. Full article

Many special structures such as pipeline, revolving gears, and tanks suffer from biofouling used in marine environment, which could induce serious results in the ship system such as blockage and stuck, consequently lead to failure of the mechanical system and power system. Generally, coatings with antifouling agents are used for protecting metal structures from biofouling, but coatings are not conveniently applicable in the high velocity flowing seawater and narrow space. Electrochlorination and electrolysis of copper and aluminum anode are usually used in these circumstances, but the electric power will lead to stray current corrosion to the component. For the sake of convenience and safety, Cu-Ti pseudo alloy antifouling anode was proposed in this work for antifouling in pipeline and other narrow spaces without external electric power. Four Cu-Ti pseudo alloy antifouling anodes with different Ti contents (mass fraction) of 0 wt.%, 5 wt.%, 10 wt.%, and 15 wt.% were investigated with computational method, and a 15 wt.% Ti content Cu-Ti pseudo alloy antifouling anode was prepared by cold spray, and the microstructure and composition of the anode were observed by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). Electrochemical tests were conducted to obtain the corrosion potential, potentiodynamic polarization curve, and micro zone electrochemical information in natural seawater, and the Cu ions releasing behavior were analyzed using inductively coupled plasma (ICP). The results indicated that in natural seawater, copper particles, and titanium particles on the surface of anode samples can form micro galvanic couples. With the increase in Ti mass fraction, the number of micro primary cells composed of copper particles and titanium particles increases, and the corrosion rate of Cu particles increased. When the Ti mass fraction is 15%, the corrosion rate is the fastest, and the copper ion release rate increases by nearly ten times, reaching 147 μg/(cm²·d). This method can effectively accelerate the releasing rate of Cu ions in Cu-Ti pseudo alloy anode and promote the antifouling effect. Full article

The line contact behavior of multiscale meshing interfaces necessitates synergistic investigation spanning nano-to centimeter-scale ranges. When nominally smooth gear teeth surfaces come into contact, the mechanical–thermal coupling effect at the meshing interface actually occurs over a collection of microscale asperities (roughness peaks) exhibiting hierarchical distribution characteristics. The emergent deformation phenomena across multiple asperity scales govern the self-organized evolution of interface conformity, thereby regulating both the load transfer efficiency and thermal transport properties within the contact zone. The fractal nature of the roughness topography on actual meshing interfaces calls for the development of a cross-scale theoretical framework that integrates micro-texture optimization with multi-physics coupling contact behavior. Conventional roughness characterization methods based on statistical parameters suffer from inherent limitations: their parameter values are highly dependent on measurement scale, lacking uniqueness under varying sampling intervals and instrument resolutions, and failing to capture the scale-invariant nature of meshing interface topography. A scale-independent parameter system grounded in fractal geometry theory enables essential feature extraction and quantitative characterization of three-dimensional interface morphology. This study establishes a progressive deformation theory for gear line contact interfaces with fractal geometric characteristics, encompassing elastic, elastoplastic transition, and perfectly plastic stages. By systematically investigating the force–thermal coupling mechanisms in textured meshing interfaces under multiscale conditions, the research provides a theoretical foundation and numerical implementation pathways for high-precision multiscale thermo-mechanical analysis of meshing interfaces. Full article

Oral cavity lesions in sea turtles, particularly Caretta caretta, are relatively rare, and are typically linked to infectious agents as well as anthropogenic factors, including ingestion of marine debris or fishing gear. This report describes a juvenile Caretta caretta found in the northern Adriatic Sea with severe oral lesions affecting the choanae, alimentary tract, and larynx. A comprehensive clinical and histopathological evaluation was conducted, which revealed traumatic injuries caused by the ingestion of a polychaete, Laetmonice cf. hystrix. Mucosal biopsies in the areas of spine penetration revealed the presence of strong sub-epithelial inflammation, characterised by micro-abscesses. In addition, around some fragments of spines, the formation of microgranulomatous lesions with a tendency to encapsulation was observed. Treatment protocol involved the removal of embedded spines and administration of a broad-spectrum antibiotic to prevent secondary infections. Recently, the detection in polychaetes of the aetiological agents of two newly emerging diseases of shrimps, suggests that these worms can be a host or/and passive carrier of these pathogens. This case study underscores the necessity to consider both biological and anthropogenic factors in diagnosing and managing oral lesions in marine turtles. Furthermore, it draws attention to the ecological risks posed by interactions between sea turtles and benthic organisms. Full article