Oil film mixed lubrication of heavy-load friction pairs: Theoretical modeling, solution methods, and applications

Pomelo peel waste was valorized through an ultrasound-assisted integrated strategy to simultaneously recover pectin and essential oil for the fabrication of active biodegradable packaging films. Ultrasonic cavitation significantly promoted cell wall disruption and mass transfer, enabling the efficient co-extraction of pectin and essential oil in a single process. The essential oil was further converted into a stable nanoemulsion via ultrasonic emulsification and incorporated into a pectin/polyvinyl alcohol/carboxymethyl cellulose composite film. The physicochemical, structural, mechanical, and aroma-related properties of the films were systematically characterized by FTIR, XRD, tensile analysis, and electronic nose. The optimized film exhibited balanced mechanical performance with a tensile strength of 6.27MPa, an elongation at break of 5.52%, and a light transmittance of 43.52%, indicating good flexibility and optical properties. Sensors responsive to nitrogen- and sulfur-containing compounds showed higher signals, likely due to oxidative transformation products rather than native sulfur volatiles. The preservation performance was evaluated using fresh strawberries as a model system. Compared with the control group, the ultrasound-enabled essential oil film effectively reduced weight loss, delayed microbial spoilage, and extended the storage life by nearly five days at room temperature. This study demonstrates that ultrasound not only intensifies the sustainable extraction of functional biopolymers but also regulates the structural assembly and release behavior of active packaging films. The proposed strategy provides a green and scalable route for converting Citrus processing waste into high-value antimicrobial packaging materials.

Water contamination threatens the lubrication stability of thrust bearings in hydro-generator units. This study investigates the coupling effects of inlet oil temperature, rotational speed, and water content (0–200 g/L) on lubrication performance. The results show that water content below 1 g/L has negligible effect. A critical threshold of 70 g/L is identified, where pad temperature rise rate increases sharply; at 45 °C inlet temperature, outlet zone temperature reaches 73 °C, and film thickness decreases to 12 μm. A water content of 100 g/L corresponds to the maximum friction torque of 9 N·m. Increasing rotational speed enhances hydrodynamic effects; at 25 m/s and 70 g/L, peak pad temperature reaches 72 °C. When water content exceeds 100 g/L, thermal buffering of free water mitigates temperature rise, but fluctuating oil film load-carrying capacity requires vigilance. The findings provide theoretical support for condition assessment and maintenance of thrust bearings under water-contaminated conditions.

The lubrication state during plastic working is affected by the process conditions. It is known that changes in working speed and reduction of area cause changes in oil film thickness, and in situ observation is effective for quantitative evaluation. Therefore, the oil film thickness during flat drawing was measured by in situ observation using the fluorescence method. As the reduction of area increased, the oil film thickness in the parallel zone decreased, but the coefficient of friction decreased. This is thought to be due to the difference in lubrication conditions between the tapered zone (fluid lubrication) and the parallel zone (mixed lubrication) of the tool. Generally, as fluid lubrication has a lower coefficient of friction, the increase in the reduction rate leads to an expansion of the fluid lubrication region, which is considered to cause the decrease in the coefficient of friction.

This study investigated the combined effects of oil concentration, emulsifier type, and saliva on the lubrication behavior of casein-based oil-in-water emulsions to support the design of milk-based foods with optimized mouthfeel. Emulsions stabilized with Tween 20, whey protein isolate (WPI), or sucrose ester were prepared at oil concentrations ranging from 0.01% to 3%, and their viscosity, microstructure, tribological properties, and ζ-potential were systematically characterized, with human saliva incorporated to simulate oral conditions. Oil concentration did not significantly alter viscosity, although droplet aggregation increased with higher oil levels. Lubrication performance was governed primarily by emulsifier type: Tween 20 generated an oil film at approximately 0.2% oil, WPI exhibited progressively enhanced lubricity with increasing oil concentration, and sucrose ester produced consistently poor lubrication due to its rigid interfacial layers. Saliva addition improved lubrication across all systems and reduced oil precipitation by promoting the formation of smaller, more stable structures. These findings demonstrate that emulsifier selection is central to modulating oil-protein-saliva interactions, with WPI at moderate oil levels yielding favorable lubrication with controlled oil release, thereby providing a mechanistic basis for developing healthier, palatable milk-based foods.

Sliding shoe bearings are crucial components supporting the rotating cylinder in grinding mills. The structural parameters of oil cavities on their inner surface significantly affect both the load capacity and lubricating oil flow rate. To address the issues of excessive oil film load and oversupply of lubricating oil in a specific type of sliding shoe bearing, a simulation model of the oil film for the hollow shaft was developed. This study investigates the effects of key oil cavity parameters—sealing land width, throttling land width between main and auxiliary cavities, and their area ratio—on bearing performance. After validating the model via hydrostatic tests on a single sliding shoe, response surface methodology (RSM) and an improved multi-objective particle swarm optimization (MOPSO) algorithm were applied to optimize the oil cavity structure. Results demonstrate that both individual and coupled parameters considerably influence oil film load characteristics. Post-optimization, the bearing’s load capacity was reduced by 3.4% while still meeting mill requirements, and the oil supply flow rate was decreased by 17.3%, leading to improved efficiency and operational safety.

Postharvest fungal decay is a primary cause of losses in blueberries, motivating the development of sustainable alternatives to conventional fungicides. This study aimed to develop and evaluate antifungal active films based on polylactic acid (PLA) enriched with citronella essential oil to control phytopathogenic fungi associated with blueberry spoilage. PLA films containing 7.5, 10, and 12.5% (w/w) citronella essential oil were produced by solvent casting and characterized for water vapor transmission rate and nanomechanical properties. The antifungal effect was tested in vitro against Epicoccum nigrum, Alternaria alternata, and Cladosporium herbarum. Active films exhibited concentration-dependent antifungal activity, with C. herbarum being the most sensitive fungus. The incorporation of citronella essential oil did not significantly alter the water vapor barrier properties of PLA, while mechanical analysis revealed a reduction in elastic modulus only at the highest concentration. The antifungal mechanism was elucidated using scanning electron microscopy, fatty acid profiling, absorbance at 260 nm, and conductivity measurements. The results indicate that the released citronella essential oil induced membrane disruption and morphological damage in fungal hyphae, with species-specific responses. Overall, PLA-citronella essential oil films represent a promising biodegradable packaging solution to control postharvest blueberry losses.

Marine oil film identification based on GLOH, K-Means and adaptive threshold.

Microbiologically influenced corrosion of oil-water pipeline steel from local field failure case to specific Shewanella & Desulfovibrio corrosion highlights the significance of hydrocarbon-degrading bacteria.

A novel resistance-based method for measuring oil film thickness on face gear tooth surfaces

Abstract With the trend toward larger-scale wind turbines, planetary gear bearings in wind turbines are undergoing a transition from rolling bearings to laser-cladded journal bearings. Using a combined numerical and experimental approach, this study investigates the influence of material porosity induced by laser cladding on the lubrication and tribological performance of gearbox journal bearings. A computational model incorporating porous material properties was developed, taking into account pore morphology, elastic deformation, and contact pressure. The accuracy of the model was validated through experiments conducted at both the material level and the full-scale wind power bearing level. The results demonstrate that applied loads from 1000 to 2000 kN predominantly drive volumetric wear within the central bearing zone, whereas wear depth at the periphery exhibits reduced sensitivity to these load variations. Porosity analyses reveal three critical regimes: Low porosity exhibit negligible wear influence compared to surface roughness randomness. Moderate porosity disrupts hydrodynamic lubrication, generating stress concentrations that accelerate wear. High porosity significantly increases wear within central bearing zones through oil film fragmentation and intensified stress focusing.

Purpose This study proposes a dual-threshold tolerance optimization method for bearing dimensions based on the oil film formation capability, aiming to address the lubrication failure issue of sliding bearings caused by improper clearance design. Design/methodology/approach In this study, by adopting the finite element method based on the Reynolds equation and taking into account the influence of contact pressure during the operation of journal bearings, the lubrication characteristics of engine main shaft journal bearings under the working conditions of different loads and rotational speeds are systematically analyzed, and the tolerance zone range is optimized based on this analysis. Findings Excessively small clearance leads to a sharp increase in fluid shear resistance and an abnormal rise in torque; huge clearance weakens the hydrodynamic effect, promotes the transition of the lubrication state to mixed lubrication, causes a significant increase in contact pressure and intensifies the wear risk. Based on this, a dual-threshold tolerance optimization method is proposed: the convergence point of torque variation with clearance is taken as the lower tolerance limit, and the final zero point of contact pressure is taken as the upper tolerance limit. Originality/value The tolerance design method and determined tolerance range proposed in this study provide a theoretical basis and practical guidelines for optimizing the design of journal bearings and improving their lubrication reliability and service life. This method can be popularized and applied to the bearing tolerance design of other heavy-load, high-speed key equipment.

Luminescent thermometry has emerged as a powerful tool for remote temperature sensing, yet the development of sustainable materials that combine robust photophysical performance with environmental compatibility remains a challenge. Herein, we report a bio-derived luminescent thermometric film obtained by incorporating the europium-based complex [Eu (tta)3(PIB)] into a castor-oil-based alkoxysilane polymer (SiCO). The resulting luminescent films are transparent, stable, and preserve the structural integrity and optical characteristics of the trivalent europium (Eu3+) complex, as confirmed by spectroscopic analyses. Efficient ligand-to-metal energy transfer gives rise to well-defined Eu3+ emission, while residual ligand-centered luminescence enables a ratiometric thermometric approach. Temperature-dependent photoluminescence measurements reveal distinct thermal quenching behaviors of the ligand and Eu3+ emissions, allowing reliable temperature readout through an intensity ratio thermometric parameter. The optimized SiCO-0.25Eu film exhibits a maximum relative thermal sensitivity of 1.31% K−1 at 189 K and a minimum temperature uncertainty of 0.43 K at 173 K, maintaining stable performance over a broad low-temperature range (42–282 K) and under repeated thermal cycling. These results demonstrate that castor-oil-derived polymer matrices can serve as efficient and sustainable platforms for luminescent thermometry, offering a promising route toward environmentally friendly luminescent temperature sensors for low-temperature applications.

Every year, significant amounts of non-biodegradable, toxic lubricants enter the environment. While legislative measures are being taken to reduce the environmental impact of this pollution, demand for environmentally acceptable lubricants (EAL) is increasing. These EALs differ in terms of their base oil and additives, thereby having a significant influence on the degradation behavior and degradation-related changes of tribological performance like oil film formation or boundary layer formation. However, the sensitivity of EALs to different degradation paths is not yet known. Therefore, the aim of this study is to determine the sensitivity of different lubricants to degradation based on their change in tribological performance. For this purpose, an ester- and polyglycol-based EAL as well as a mineral oil (polyalphaolefin) were degraded synthetically by oxidative and hydrolytic degradation. The degraded lubricants are visually, rheologically and chemically analyzed. In addition, the tribological performance in terms of oil film formation and tribological boundary layer formation was studied in a ball-on-disc tribometer. Afterwards the results are compared to their corresponding fresh lubricants. For the tested ester-based EAL no significant sensitivity to degradation could be shown, as no significant change in tribological performance occurred. Both polyalphaolefin and polyglycol proved to be sensitive to degradation leading to a significant reduction in the tribological boundary layer thickness. These results show, that mineral oil-based lubricants and EALs, as well as EALs themselves, differ in terms of their sensitivity to degradation. These effects must be considered in qualification process of lubricants.

Purpose The elastic ring squeeze film damper (ERSFD) is a key element of the high-speed rotor system in aero-engine. By far, the dynamic characteristics of ERSFD has not been investigated throughout. The purpose of this study is to investigate the dynamic behaviors of the ERSFD oil films considering the fluid inertia effect with using the perturbation method. Design/methodology/approach The perturbation equations for the ERSFD, including the journal’s acceleration perturbations, are derived by using the Taylor series expansion, and a comparative study of the oil film dynamic behaviors between the perturbation method and the parameter identification method is conducted. Findings The dynamic coefficients of ERSFD exhibit periodic change during an entire circle of whirling; the dynamic coefficient of the inner oil film is an order of magnitude larger than that of the outer oil film; the cross-coupled coefficients of the ERSFD’s oil film cannot be disregarded; the fluid inertia effect can increase the direct stiffness and damping coefficients. Originality/value The perturbation method can be used to calculate the complete dynamic characteristics of the ERSFD with the attitude angle, including the direct and cross-coupled dynamic coefficients. This work contributes to existing knowledge of ERSFD by providing a detailed analysis of dynamic coefficients.

The sliding shoe bearing serves as a critical rotary support component in large grinding mills. The deformation of the hollow shaft under operating conditions is a pivotal factor governing the uniformity and stability of the lubricating oil film thickness in sliding shoe bearings. To address this, a finite element model of the sliding shoe bearing system, comprising the lubricating oil film and hollow shaft, was established based on fluid–structure interaction (FSI). The model’s predictions for oil cavity pressure and hollow shaft radial displacement were validated using a custom-built test rig designed for single-shoe sliding shoe bearing oil pressure measurements. Utilizing this finite element model, the relationship between hollow shaft deformation and oil film pressure distribution was systematically investigated. The study analyzed the effects of key parameters—specifically the area ratio of the primary and secondary oil chambers, radial load, secondary oil chamber supply pressure, and primary oil chamber supply orifice diameter—on the axial and circumferential deformation of the hollow shaft. The results indicate that the oil film pressure distribution directly influences the deformation of the hollow shaft. The area ratio of the oil chambers emerges as the dominant factor affecting this deformation. Furthermore, radial load exerts a significant impact, whereas the influence of the secondary oil chamber supply pressure is relatively minor. Conversely, the inner diameter of the primary oil chamber supply orifice exhibits a negligible effect on the hollow shaft deformation.

This study evaluated the effects of chitosan composite edible coatings with frankincense essential oil on microbial growth and strawberry quality. Four coatings were prepared using 1% and 3% chitosan aqueous solutions, with or without 1% (v/v) frankincense essential oil derived from Boswellia sacra. Fresh strawberries were coated with chitosan and chitosan–frankincense solutions and stored under controlled conditions for eight days. The physical properties of strawberries, such as color, texture, moisture content, pH, and total soluble solids, were evaluated throughout the storage period. Results indicated that neither chitosan nor chitosan–frankincense oil coatings significantly altered the physical properties of the strawberries, such as the color, pH, moisture content, total soluble solids, and hardness at each time point. However, a significant effect of time (2-way ANOVA, p < 0.05) was observed on pH, TSS, color and hardness characteristics of strawberries. All tested coatings effectively inhibited bacterial growth. The strawberries covered with 3% chitosan–frankincense oil coating had the lowest bacterial count (74 CFU/mL). The addition of frankincense to 1% of chitosan significantly reduced the number of bacteria by 1.6-fold. Additionally, chitosan–frankincense oil films significantly reduced the growth of E.coli compared to both the chitosan film and the control. These findings suggest that chitosan combined with frankincense oil can serve as an effective natural alternative for edible coating in food preservation, offering both antimicrobial benefits and quality retention during storage.

Offshore oil exploration and the volume of imported crude oil shipping have increased steadily, elevating the risk of oil spills. An advanced offshore oil film identification method is proposed to realize the accurate and robust recognition and segmentation of oil films from marine radar images in offshore oil spill detection. This method integrates feature engineering with an improved Beetle Antennae Search (BAS) optimization algorithm, aiming to address the key issues of low discrimination between oil films and complex marine backgrounds and insufficient spill boundary localization accuracy in radar image analysis. First, the raw radar image was transformed into the Cartesian coordinate system, and a filtering procedure was applied to attenuate interference. Subsequently, the gray distribution and local contrast of the denoised image was further improved. Afterwards, the complexity of the grayscale distribution within each feature map was quantified using Shannon entropy. The Top-K feature maps with the highest entropy values were subsequently used to construct an information-rich subset. The subset was then processed through a pixel-wise averaging strategy to generate a coupled feature image. Then, Otsu threshold was used to refine ocean wave regions. Finally, the oil films were segmented with an improved BAS optimization algorithm. The fitness function of the improved BAS algorithm was augmented through the integration of edge fitting accuracy, and a target-proximity penalization scheme. Through an adaptive step-length modulation paradigm and Perceptual Mechanism, it can achieve a marked improvement in search accuracy and achieving precise segmentation of oil slicks. The detection accuracy of the proposed method is significantly enhanced relative to the traditional BAS algorithm and existing marine radar oil spill detection methods. The IOU, Dice, recall and F1-score reached 81.2%, 89.6%, 85.2%, and 90.1% respectively. This method not only advances the methodological rigor of spill detection but also provides critical data support for the development of more effective control and remediation practices.

Accurately predicting gear meshing excitation is crucial for high-performance transmission fatigue design and noise optimization. To address the frequently overlooked topography-lubrication coupling, this paper presents a loaded tooth contact analysis (LTCA) model integrating ground surface features and oil film stiffness. Utilizing the finite element substructure method, the model combines a non-uniform sinusoidal function for surface waviness with the Dowson-Higginson film thickness formula. Results show that higher grinding wheel speeds enhance surface quality, bringing time-varying meshing stiffness (TVMS) and static transmission error (STE) levels closer to ideal smooth surfaces. Conversely, increased axial feed rates or fluctuation amplitudes deepen surface textures, causing stiffness attenuation and a significant STE amplitude surge. Additionally, higher lubricant viscosity, pressure-viscosity coefficients, or driving gear speeds thicken the oil film, reducing equivalent stiffness and elevating global transmission error. Crucially, the roughness-oil film coupling causes the most severe stiffness loss. This study offers a precise theoretical foundation for predicting precision gear system contact characteristics.

Abstract This study focuses on the film-forming characteristics of the secondary lubricating medium in a water environment under different working conditions, and the roller-on-disc lubrication film test rig, along with the fluorescent approach, is used to directly observe the film formation of the secondary lubricating medium. Observations reveal that working conditions of higher load and higher speed can decrease the film-forming ability of the secondary lubricating medium but benefit the stability of the oil film thickness. The block-on-ring test rig and the confocal microscopy are used to prove the characteristics of friction and wear reduction of the injected secondary lubricating medium, and the flow condition of the secondary lubricating medium in the contact region of the block-on-ring test rig is then simulated by using the CFD model. This research facilitates the adoption of environmentally friendly lubricants as the secondary lubricating medium in engineering applications lubricated with pure water by providing essential data support.