Search Results (385)

Mechanical seal faces frequently operate under harsh and dynamic conditions, where maintaining stable and efficient lubrication remains a critical challenge. Surface texturing has emerged as an effective approach to improve the lubrication and tribological performance of sealing end faces. This study investigates the lubrication behavior and sealing characteristics of squamous textured mechanical sealing faces through a combination of sealing experiments and mixed lubrication modeling. The results indicate that during start-up, increasing rotational speed enhances the load-carrying capacity and reduces contact force, resulting in thicker lubricant films and lower friction coefficients. Consequently, the sealing interface gradually transitions from mixed to hydrodynamic lubrication. Moreover, with increasing medium pressure, both the critical rotational speed and duration required for this lubrication regime transition increase. Under various steady periods, smooth seal faces predominantly operate in the mixed lubrication regime, whereas textured faces maintain hydrodynamic lubrication, reducing the average friction coefficient and temperature rise by 69.5% and 51.8%, respectively. These findings provide crucial insights into the performance improvement and practical applications of squamous textures for high-efficiency, long-lifespan mechanical seals. Full article

This study investigates how cooking oil-based cutting fluids (CKO-CFs) perform as sustainable alternatives to conventional mineral oil-based fluids when turning AISI 1020 mild steel. Waste cooking oil was cleaned, treated, and mixed with selected additives to improve stability, lubricity, and corrosion resistance. Machining experiments were designed using the Taguchi L9 orthogonal array to optimise cutting speed, feed rate, and depth of cut. The CKO-based cutting fluid showed lower surface roughness at 0.270 μm compared to conventional cutting fluids at 0.274 μm. This indicates better lubricity and a smoother surface finish. Tool-tip temperatures were reduced by up to 11.99% compared to conventional fluids. This improves heat dissipation and lowers thermal damage. Tool wear was reduced by up to 5.75% with the CKO-based fluid, suggesting better lubrication and a longer tool life than conventional cutting fluids. The findings show that CKO-based cutting fluids provide an eco-friendly and efficient option for sustainable machining operations. Full article

Despite the growing adoption of Ti6Al4V-ELI made by Laser Powder Bed Fusion (LPBF) in tribologically demanding applications, the influence of hybrid nanoparticle additives on its lubrication behavior under starved contact conditions remains insufficiently explored. The tribological performance of Ti6Al4V was investigated under starved boundary-to-mixed lubrication conditions using engine oil modified with Ag-doped TiO₂ nanoparticles. Double-scan LPBF-fabricated discs were tested in a ball-on-disc configuration against AISI 52100 bearing steel using a TRB³ tribometer. Nanolubricants were prepared by dispersing TiO₂ and Ag–TiO₂ nanopowders with different Ag⁺/Ti⁴⁺ ratios (0.5%, 1.5%, and 2.5%) in SAE 10W-40 engine oil at a constant nanoparticle concentration of 0.05 wt%. Comprehensive physicochemical characterization of the nanopowders and nanolubricants was performed through structural, chemical, optical, morphological, rheological, and stability analyses. Tribological experiments were conducted following a full-factorial design combining three normal loads (5–15 N), three sliding speeds (0.10–0.20 m·s⁻¹), and four lubricant formulations. The steady-state coefficient of friction ranged between 0.281 and 0.359, while the specific wear rate varied from 2.81 × 10⁻⁴ to 4.83 × 10⁻⁴ mm³·N⁻¹·m⁻¹. The contact temperature rise remained relatively moderate, within the interval of 1.9–9.4 °C. Among the investigated formulations, the lubricant containing 1.5% Ag–TiO₂ exhibited the lowest friction coefficient, whereas the formulation with the highest Ag content showed improved stability of tribological performance across the investigated operating domain. These results indicate that Ag-modified TiO₂ nanoparticles are consistent with the formation of protective tribofilms and contribute to the stabilization of friction, wear, and thermal behavior under starved lubrication conditions. ANOVA confirmed that sliding speed and the load–lubricant interaction are the dominant factors governing friction and wear, while normal load controls the thermal response. These findings support the use of Ag–TiO₂ nanolubricants as a viable strategy for stabilizing interfacial behavior in LPBF-fabricated titanium components operating under starved lubrication conditions. Full article

Lamellar ichthyosis is a rare congenital disorder of keratinization frequently associated with ocular complications, most commonly cicatricial ectropion and exposure keratopathy. We present a case of severe mixed exposure-related and neurotrophic keratopathy with marked corneal thinning in a 61-year-old man with genetically confirmed lamellar ichthyosis. At presentation, the best-corrected visual acuity (BCVA) in the right eye was limited to hand motion (logMAR 2.3). Slit-lamp examination revealed a large central to inferocentral corneal ulcer measuring approximately 3 × 4 mm with severe stromal thinning in the setting of marked lower eyelid ectropion, incomplete eyelid closure, and chronic ocular surface exposure, while anterior segment optical coherence tomography (AS-OCT) demonstrated a minimal corneal thickness of approximately 165 µm. Microbiological swabs obtained from the conjunctival sac were negative, and no purulent discharge, hypopyon, or anterior chamber inflammatory reaction was present, making active infectious keratitis unlikely. Corneal sensitivity measured with Cochet–Bonnet esthesiometry at presentation, centrally and in all four peripheral quadrants of both eyes, was markedly reduced, more severely in the affected right eye, supporting the presence of a severe neurotrophic component contributing to impaired corneal healing. Intensive conservative therapy including preservative-free lubricants, dexpanthenol gel, autologous serum eye drops, topical insulin, prophylactic antibiotics, and systemic doxycycline was initiated. Serial AS-OCT imaging demonstrated progressive structural recovery, with corneal thickness increasing to 438 µm after one month of treatment and complete corneal epithelialization. The BCVA improved to 0.2 Snellen (0.7 logMAR). This case highlights the diagnostic value of multimodal anterior segment imaging in monitoring severe mixed keratopathy with advanced corneal thinning and demonstrates that intensive conservative therapy may stabilize the ocular surface and prevent corneal perforation in patients with lamellar ichthyosis. Full article

Reclaimed asphalt pavement (RAP) is a large but underutilized resource for sustainable concrete production; however, its use in structural applications is limited by concerns regarding reduced workability and durability. This study investigates the interactions between RAP and silica fume (SF) as well as superplasticizer (SP), and identifies optimal RAP concrete mixtures through the individual incorporation of SF and SP to enhance workability, durability-related indicators, water absorption, and density. RAP replaced 0–100% of coarse aggregate, SF was added at 0–21%, and SP at 0–2.1%, with a fixed water–cement ratio of 0.48. Six mix categories were prepared: control, RAP, SF, SP, RAP–SF, and RAP–SP. SF and SP were examined separately to isolate their interactions with RAP before they were combined with other cementitious materials. RAP increased slump via a lubricating effect but increased water absorption, with the density stabilizing at 50% RAP and peaking at 75% RAP due to improved particle packing. Although SF’s influence was limited by the fixed w/c ratio, in moderate-to-high (50–100%) RAP mixes it achieved very low water absorption (≤1.1%) and increased density (up to 7.6%), confirming its pore-refinement effect. SP achieved the greatest workability gains (up to 58% slump increase) at high RAP levels but contributed less to durability, highlighting SF’s stronger pore-refinement role. Most RAP–SF and RAP–SP mixes satisfied severe-environment durability limits, confirming their potential for sustainable, high-performance RAP concrete without compromising structural reliability. Full article

Issues related to the environmental safety of transport vehicles, the operation of which leads to environmental pollution, continue to be highly relevant. In this work, we consider the use of biofuel mixed with diesel fuel for internal combustion engines operating at low temperatures. This approach does not reduce the efficiency of transport, while also solving the issue of organic waste recycling. In this work, we address the possibility of reducing environmental pollution using carbon-neutral blended fuels based on esters of waste cooking oil (WCO), biobutanol, and diesel fuel for transport, tractor, and other equipment powered by a diesel internal combustion engine. In terms of the rate of biofuel implementation, Russia is still lagging behind the EU, China, and Japan, largely due to, inter alia, its climatic conditions with cold and long winters. The article also provides data on the possibility of using mixed biofuels under sub-zero temperatures. The process of forming a volumetric fuel supply through the common rail injector of the D4CB engine under changes in fuel pressure and drive pulse duration was also investigated, with the corresponding regression dependencies being presented. The losses of heat supplied into the cylinder when using a blend of diesel fuel and biodiesel (with 20 wt% butanol) in comparison with diesel fuel were analytically calculated. This made it possible to identify a function for adjusting fuel supply to compensate for power losses. The lubricity of fuel blends was assessed using the HFRR method. Full article

The effects of dust, copper particles, and iron particles on the high-temperature oxidative degradation behavior of aviation lubricating oil were systematically examined, and the high-temperature catalytic oxidation effects of single-particle and mixed-particle systems on the lubricating oil were further analyzed, respectively. Gas chromatography/mass spectrometry analysis results indicated that significant differences exist in the catalytic oxidation activity of particles toward lubricating oils, with the activity ranking in the descending order of copper particles > iron particles > dust. Notably, following oxidation by both metal and dust particles, the acid value, particle size, and viscosity of the oil sample exhibit a significant synergistic catalytic effect, even exceeding those of the oil sample oxidized by the same amount of metal particles. Specifically, relative to the pristine oil, the oil oxidized with 5 mg of copper particles and 5 mg of dust exhibits respective increases of 213.3%, 316.11%, and 661.43% in the aforementioned properties. This variation is attributed to the physical adsorption and chemical reactions between dust and antioxidants during oxidation, which deplete antioxidants and thereby exacerbate oil oxidation. Furthermore, this study further elucidates the potential synergistic oxidation mechanism induced by metal particles and dust particles. Full article

Ti₃C₂T_x/Al6061 composites were fabricated via vacuum induction melting, with systematic analysis conducted on their microstructure, mechanical properties, and wear behavior. Findings indicate that Ti₃C₂T_x addition significantly refined the composite grain size. Uniformly dispersed Ti₃C₂T_x particles promoted heterogeneous nucleation, reducing the average grain size by 44.7% compared to the matrix at the optimal 2 wt.% addition. Strong interfacial bonding ensured efficient load transfer, resulting in a 48.4% increase in tensile strength for the 2 wt.% Ti₃C₂T_x/Al6061 composites compared to the matrix alloy, while elongation decreased by 11.7%. Tribological analysis revealed that the wear rate of 2 wt.% Ti₃C₂T_x/Al6061 composites increases with applied load but remained substantially lower than Al6061 under all tested conditions. This excellent wear resistance is attributed to the synergistic effect of the protective mechanically mixed-layers formation and the inherent self-lubrication property of Ti₃C₂T_x during sliding contact. With increasing load, the friction coefficient and tendency for microcracking on the worn surface of the composite increased, and the dominant wear mechanisms transitioned from abrasive and adhesive wear to delamination wear. Full article

Oily substances (oils, greases, lubricants, etc.) are among the most persistent pollutants for water. They mix with water to form emulsions that contaminate large volumes. Therefore, this project evaluated the use of porous systems (polyurethane foam) modified with polydimethylsiloxane-modified silica (SiO₂/DMS) hybrid ceramics as filtration membranes at the laboratory scale for vegetable oil. The polyurethane foam was modified using sol solutions with various SiO₂/PDMS ratios obtained via the sol–gel method. Tetraethyl-orthosilicate (TEOS) was used as the silica precursor. Three different polydimethylsiloxane chains were employed as the organic fragment: polydimethylsiloxane hydroxyl terminated (DMS-CH₃), aminopropyl-terminated polydimethylsiloxane (DMS-N), and copolymer polydiphenylsiloxane-polydimethylsiloxane hydroxyl terminated (PDS). The siloxane chain was added at a concentration of 20–40% w/w. The modification of the porous system was determined using different characterization techniques, including infrared spectroscopy, which was used to observe the main functional groups. Optical microscopy and SEM were used to identify the hybrid ceramic deposited into the pore structure of the polyurethane sponge. Contact angle measurements revealed the hydrophobic character of the modified material. The removal capacity was evaluated by using vegetable oil as a representative oily contaminant, with values ranging from 43.42 to 96.78 g of oil per gram of adsorbent. In the case of gasoline, removal capacities between 27 and 54 g were observed. This study demonstrated the influence of hydrophobicity on vegetable oil removal, confirming that higher hydrophobicity leads to greater adsorption capacity. Nevertheless, the use of a viscous contaminant introduced challenges in the extraction process from the PS/SiO₂-DMS system. Despite this limitation, the material maintained adequate removal performance for up to five reuse cycles. On the other hand, the removal capacity depends on the amount of polysiloxane chain in the ceramic, as well as the functional group, exhibiting the following behavior: DMS-N < DMS-CH₃ < PDS. This study demonstrates that hydrophobicity is a key property for enhancing the removal capacity of oily substances. Moreover, the control of intermolecular interactions further strengthens this effect, as evidenced in the PS/SiO₂–PDS system. Full article

Reducing friction in the piston ring–cylinder liner contact is a key area for improving the efficiency of internal combustion engines. While tribological studies commonly focus on the top dead centre region using linear tribometers, the mid-stroke regime—with its higher sliding velocities—remains experimentally inaccessible to most conventional test methods. This study presents a rotating ring-on-liner tribometer that enables investigations at constant relative speed by transitioning the motion from oscillating to rotating. A cylindrical substitution geometry for the piston ring specimen is derived through a coupled elastohydrodynamic and asperity contact simulation approach to reproduce realistic load-sharing behaviour. Experimental results from starved lubrication tests demonstrate stable contact conditions with a low coefficient of variation in wear, confirming good reproducibility. Stepwise performed Stribeck tests at 40 °C and 100 °C reveal characteristic friction–velocity behaviour, including the transition from mixed to hydrodynamic lubrication. Although the test rig’s maximum sliding speed and steady-state thermal conditions differ from fired engine environments, the methodology closes an important gap between low-speed linear tribometers and complex floating-liner systems. The presented approach provides a flexible and robust platform for controlled parametric studies of ring-on-liner contacts under application-relevant lubrication regimes. Full article

Braking drag is a typical fault of brake systems, and clarifying the correlation mechanism between vehicular working conditions and braking drag is critical for brake design improvement. Based on fluid mechanics and contact mechanics, this paper establishes a dynamic model for braking drag mechanism analysis, combined with the return mechanism and force-bearing state of brake pistons. Firstly, a commercial vehicle brake system dynamic model is built via Amesim, and piston sliding resistance is identified as the key factor leading to insufficient piston retraction through user operational data analysis. Subsequently, a fluid-structure interaction-based dynamic coupling model of drag mechanism is established, typical braking conditions are extracted via K-means clustering, and piston friction, displacement and drag torque are solved with the system model outputs as inputs. Finally, drag-prone working conditions are determined, and the disc brake drag mechanism is revealed. The results show that piston sliding resistance is the primary factor in braking drag; medium-low speed prolonged braking has high drag susceptibility; and the seal contact area is in mixed lubrication, with contact pressure and friction dominated by asperity shear stress. This work enables accurate identification of drag-prone conditions, providing guidance for brake system optimization. Full article

This study was conducted to investigate and identify correlations among sensory and comprehensive consumer test results with rheological, textural, and tribological properties of milk chocolate in response to varying levels of particle size and emulsifier. To simulate realistic oral conditions, artificial saliva was incorporated into instrumental analyses. Rheological analysis revealed that increasing particle size and emulsifier concentration significantly reduced plastic viscosity, while emulsifier concentration alone increased yield stress due to structural reorganization within the fat phase. Tribological measurements demonstrated that larger particles increased friction in boundary and mixed lubrication regimes, whereas emulsifiers reduced friction in these regimes by enhancing fluid film formation. Under elastohydrodynamic conditions and with artificial saliva, friction was more influenced by the interaction between particle size and emulsifier level. Textural analysis showed that both parameters significantly influenced hardness, with saliva further softening the samples, especially those with higher emulsifier levels. Sensory evaluations indicated that emulsifiers enhanced flavor release and mouthfeel attributes, while smaller particles contributed to smoother texture and more balanced flavor perception. Consumer acceptance tests confirmed that samples with smaller particles and higher emulsifier levels received the highest scores in overall liking, taste, and texture. Instrumental parameters strongly correlated with key sensory attributes, with yield stress showing the highest positive associations with creaminess, smoothness, fat/milk flavor, and liking, while higher viscosity and friction were negatively linked to flavor release and mouthfeel. Instrumental hardness negatively correlated with cacao intensity and astringency, while saliva-induced softening was positively associated with sweetness and liking, highlighting the role of dynamic oral softening. Full article

Dysphagia is common among older adults and frequently necessitates the use of thickening agents to facilitate safe swallowing of medicines, which may in turn alter their bioavailability. This study investigated the impact of two commercially available lubricants—Gloup^® Forte and extremely thick water—on the in vitro dissolution behaviour of immediate-release gliclazide tablets. Dissolution studies were conducted using crushed and whole tablets in different media consisting of reverse osmosis water, phosphate buffer (pH 6.8), and 0.1 N HCl at 37 °C. Dissolution profiles were compared using similarity factor (f₂) analysis and modelled using established kinetic equations. Gliclazide dissolution was significantly delayed in the presence of Gloup^® Forte across all media for both crushed and whole tablets, with f₂ values below 50, indicating dissimilar profiles. Dissolution kinetics confirmed that mixing the formulated gliclazide with Gloup^® Forte delayed the release and reduced the dissolution rate constant for drug from both crushed and whole gliclazide tablets in media studied. Full article

A significant amount of frictional heat is generated during the braking process of mine-used monorail cranes under heavy-load and low-speed creeping (or reciprocating speed regulation) conditions, causing thermal softening and performance degradation of the brake pads. Thus, investigating the tribological evolution mechanism is necessary to ensure reliable braking in deep underground environments. In this paper, full-scale tribological testing technology is applied to the brake system, and the friction and wear characteristics of copper-based powder metallurgy (P/M) brake pads under complex hygrothermal environments are studied. A physical experimental model coupling normal load, sliding speed, and humidity is established using a custom-designed open-structure reciprocating tester, revealing the “load weakening effect” under dry conditions and the “dual regulation mechanism” of mixed lubrication and cooling flushing under high humidity. Then, a surrogate prediction model of friction coefficient and wear rate, with respect to the operating parameters, is constructed based on Central Composite Design (CCD) and Response Surface Methodology (RSM). The reliability of the model under non-linear working conditions is estimated based on Analysis of Variance (ANOVA) and blind tests. The results indicate that the model possesses high prediction accuracy (relative error < 5%), and the feasibility of utilizing the high-humidity environment to enhance wear resistance and stability is verified. Full article

With the development of manufacturing towards stricter precision requirements and increasingly complex geometric shapes, dimensional accuracy has become a key factor affecting precision engineering components used in many industries. Effective cooling and lubrication methods have always been a meaningful way to improve the surface quality of cutting materials. Minimum-quantity lubrication technology mixes compressed air with cutting fluid, produces a spray at ambient temperature, and guides these droplets to the cutting area under the action of high-pressure air to promote penetration into the contact area between the tool, workpiece, and chip. Minimum-quantity lubrication can be used to increase cutting speed, cool workpieces, improve workpiece quality, and significantly reduce the pollution caused by cutting fluid to the environment. However, minimum-quantity lubrication technology still cannot meet the requirements of sustainable machining in cutting processes. A test device platform for milling 6030 aluminum alloy with minimal quantity lubrication was established, and different cooling methods were used to analyze the effect on surface roughness. The spindle speed n, feed rate f, and cutting depth a_p are selected as optimization variables, with surface roughness as the optimization objective. Single-factor experiments were conducted to determine the optimal range for these variables. Subsequently, a model was constructed using the response surface methodology and solved using Design-Expert software. The interaction effects of spindle speed, feed rate, and depth of cut on surface roughness were analyzed. Additionally, genetic algorithms were employed to optimize cutting process parameters for the best combination. The results demonstrated that by combining Response Surface Methodology (RSM)and genetic algorithms, when the spindle speed n was 2520 r/min, the feed rate f was 48 mm/min, and the depth of cut a_p was 0.08 mm, the actual surface roughness after milling reached 0.148 µm, representing a 74.57% reduction compared to the initial surface roughness. This research method provides a theoretical foundation and technical support for optimizing minimal quantity lubrication (MQL) cutting processes. Full article