• Friction variations influence the vehicle dynamic behaviour and critical speed. • Loadings change the relationship between friction interfaces and critical speed. • High wheel-rail friction increases the risk of derailment in tare wagons. • Monte Carlo simulation for wagon fleets and railway performance studies. Modern multibody dynamics analyses of railway vehicles must account for the stochastic nature of friction coefficients, particularly in freight wagons with numerous friction interfaces. This is especially relevant for three-piece bogie vehicles, where friction behaviour significantly influences dynamic performance. However, most existing approaches rely on deterministic inputs, limiting their ability to reflect the variability in frictional characteristics that affect critical speed and other dynamic responses. This paper proposes a Monte Carlo simulation approach to model uncertainties in rail vehicle dynamics, enabling the exploration of diverse operational scenarios through randomised input parameters. When combined with high-performance computing, this approach allows for more comprehensive vehicle dynamics analysis compared to traditional deterministic approaches. A critical speed case study on a heavy haul vehicle demonstrates the proposed method's effectiveness. Friction coefficient variability critically influences the dynamic performance of rail vehicles, providing valuable insights for vehicle design, operational strategies, and maintenance practices. Wheel-rail interface and bogie centre plate bottom friction coefficients exert significant influence on vehicle stability, with the effects varying notably between laden and tare conditions.

Influence of adhesive type on microstructure and wear performance of SiC coated CK45 steel using GTA cladding: A cost-effective substitute for X120Mn12 alloy

The thermo-hydrodynamic (THD) lubrication performance of journal bearings is critical to the operational stability and service life of rotating machinery. To achieve a breakthrough in enhancing the THD lubrication performance of journal bearings through surface texturing, we design a novel wing-shaped texture inspired by the falcon's superior flow-guiding and pressure-converging characteristics. A three-dimensional multiphase CFD THD model is established to investigate the influence of wing-texture parameters. The wing-shaped texture is compared with commonly used textures, including rectangle, circle, and triangle designs. To address the complex geometry of the wing-shaped texture, the excessive number of design parameters, and the conflicting objectives, a quadratic response surface model is constructed using central composite design to map parameters to objectives. Multi-objective optimization is then performed by combining NSGA-II with an entropy-weighted TOPSIS method, ultimately identifying the parameter combination that yields optimal THD performance for wing-textured journal bearings. The main findings are as follows: (1) The THD performance of the wing-shaped texture is superior to that of the other three traditional textures. The coefficient of friction can be improved by up to 32.4%, and the average oil-film temperature rise is reduced by 1.08 K. (2) Placing the wing-shaped texture in the middle of the oil film's converging wedge, together with a higher circumferential placement density, delivers better THD performance. (3) After multi-objective optimization, the wing-shaped textures are concentrated at the center of the oil-film high-pressure region, thereby thickening the local film, reducing shear stress and friction, and enhancing lubricant flow and heat dissipation to suppress temperature rise. Consequently, the friction force is reduced by up to 59.3%, the load-carrying capacity increases by 20.5%, and the peak oil-film temperature decreases by 2.19 K. • Wing-shaped textures couple flow guidance and pressure convergence, cutting COF by 32.4% and oil-film rise by 1.08 K. • A 3D CFD-THD model links local flow features to pressure-temperature coordination and texture optimization. • CCD-NSGA-II-TOPSIS optimization cuts friction by 59.3%, raises LCC by 20.5%, and lowers T max by 2.19 K.

Cartilage-on-cartilage contact exhibits isotropic wear independent of fiber orientation: Experiments and biphasic finite element prediction.

Effect of pavement surface parameters on development of skid resistance properties

Polyvinyl alcohol hydrogel (PVA-H) is increasingly used as vascular modeling material due to its low friction and high transparency. Since mechanical, fluid dynamic and implant performance tests are commonly performed in aqueous environments, a thorough understanding of time-dependent changes in geometrical, mechanical and optical properties of PVA-H in water is imperative. In this study, a comprehensive analysis of the short- and long-term behavior of PVA-H in water for vascular modelling applications has been performed. PVA-H properties were investigated for six weeks, with the swelling behavior characterized by mass and area change. Young's modulus was assessed, as well as compliance for medium-sized (Ø 6.8mm) and large artery models (Ø 30mm). Friction coefficients were determined via planar sliding test and UV-Vis spectroscopy served to assess optical transparency of PVA-H. Geometric analysis revealed initial slight swelling of the PVA-H, followed by shrinkage up to -33.3±0.5 % after six weeks. Compliance increased considerably within the first hours of water exposure, followed by an increase in Young's modulus and a decrease in compliance over days to weeks. Furthermore, friction coefficients increased considerably from 0.110±0.001 after half an hour up to 1.142±0.038 after five weeks. Optical transparency initially fluctuated and subsequently stabilized above 90 % up to six weeks. In conclusion, this study provides a comprehensive understanding of short- and long-term changes in geometrical, mechanical, and optical properties of PVA-H in water, demonstrating that precise timing is required when used as models for vascular research and implant testing.

Hybrid ANN–RSM modeling and sensitivity analysis of skin friction in Sisko fluid flow over a porous exponentially stretching sheet

A microscale four-ball tribometer for characterization of lubrication by small volume samples.

The effect of silver nanoparticles (Ag-NPs) concentration in the electrolyte during micro-arc oxidation (MAO) of plastically deformed titanium of commercial purity (cp-Ti) on microstructure, adhesion and tribological performance of produced coatings was investigated within the present work. Although the effect of the Ag-NPs on the antibacterial properties and biocompatibility of MAO coatings has been barely investigated, the tribological behaviors such as sliding and fretting wear have been studied in detail. The application of phosphate-based electrolyte allowed to effectively incorporate the Ag-NPs into the MAO coating, particularly on their upper surface, without agglomeration, and in the areas close to the pores. Such a distribution of the Ag-NPs influences the scratch and wear resistance, delaying the cracking of the coating (by increasing L C1 critical load) and acting as a solid lubricant decreasing the coefficient of friction, respectively. A reduction in sliding wear rate was observed for the MAO coatings with added Ag-NPs, with a lowest value recorded for the material with 1 g/l of Ag-NPs suspended in the electrolyte (1.34·10 -6 mm 3 /N·m) as compared with the reference material without NPs (2.57·10 -6 mm 3 /N·m). A slight increase in wear rate was stated for 2 g/l (1.86·10 -6 mm 3 /N·m). The tribological response of the MAO coating with conductive Ag-NPs is governed by two competing phenomena: increasing amount of solid state lubricant (Ag-NPs) but increasingly more porous coating at the same time (due to more intense micro-arcing in the electrolyte of higher conductivity) deteriorating the wear resistance. • MAO coatings with Ag-NPs were deposited on cp-Ti substrates • Ag embed into MAO coating in original form on its upper surface and near porosity • Addition of Ag-NPs, acting as solid lubricants, reduced the friction coefficient • Wear rate reaches a minimum for the MAO coating with 1 g/l of Ag-NPs • Soft Ag-NPs on the upper surface helped to delay crack formation and propagation

Hydroxyapatite (HAp) is used as a bioactive coating because of its similarity to bone mineral, but conventional deposition methods struggle to control thickness, crystallinity, and adhesion. In this work, nanostructured HAp coatings are deposited from an aqueous suspension using an atmospheric-pressure plasma jet (APPJ), in which an ultrasonic nebulizer injects the mist into the plasma, activating the stainless-steel substrate and promoting particle self-assembly. Continuous coatings with bone-like Ca–P–O composition and elongated HAp nanocrystals (~120 × 20–25 nm) are obtained, and the thickness increases linearly from ~3 to ~9 μm with deposition time. XRD, Raman, and XPS confirm preservation of the hydroxyapatite phase without detectable secondary calcium phosphates, while contact angles (~27°) indicate a hydrophilic surface. Tribological tests show that thin (~3 μm) coatings act as adherent anti-wear layers under 1 N load, whereas thicker (~6–9 μm) coatings undergo controlled delamination and form a third-body HAp film that lowers the coefficient of friction at 2 N. APPJ enabled low-temperature fabrication of HAp coatings with thickness-dependent tribological behavior, relevant for protective and biomedical surfaces requiring controlled wear and bone-like chemistry. • APPJ deposits hydroxyapatite coatings from aqueous nanoparticle suspensions. • Coating thickness is tuned linearly from ~3 to ~9 μm by plasma deposition time. • APPJ HAp coatings preserve bone-like Ca–P–O and nanocrystalline morphology. • Thin (~3 μm) coatings act as adherent anti-wear layers under 1 N load on steel. • Thicker (~6–9 μm) coatings delaminate controllably and have lower friction.

Comprehensive study of ductile damage behavior and formability in hole expansion process

Structural design of dysphagia-oriented double emulsions via internal-external phase coordination to modulate texture, rheology, and oral lubrication.

Leveraging tabular prior-data fitted networks for accurate pavement friction coefficient prediction from 3D texture features

Time-dependent deformation is a critical factor controlling reservoir integrity and long-term storage security in organic rich shales. Yet the effect of sorbing gases on overall time-dependent and creep behaviour of organic rich shales is not fully understood. This study therefore investigates the influence of sorptive (CO 2 ) and non-sorptive (He) gases on time-dependent deformation of organic rich shale using a combined experimental and modelling approach. Triaxial poro-mechanical creep experiments on Beetaloo shale show that CO 2 exposure significantly enhances creep strain, with deformation increasing systematically as pore pressure and effective stress rise. This enhancement correlates strongly with CO 2 adsorption capacity and cumulative specimen damage, indicating that adsorption-driven swelling initiates adsorption weakening, while progressive damage provides the dominant contribution to creep strain. In contrast, helium exposure results in negligible adsorption and minimal creep, closely resembling dry conditions. Reactor-based adsorption-swelling experiments confirms the relatively minor role of free swelling strain on the overall time-dependent deformation. On the other hand, the shear tests on clay-filled fracture analogs demonstrate that CO 2 reduces the friction coefficient of the clay-filled fracture enabling further creep and damage development. To capture these coupled chemo-mechanical processes, a sorption-damage-creep model grounded in continuum mechanics and non-equilibrium thermodynamics is developed, explicitly linking adsorption kinetics, energy dissipation, and damage evolution to creep strain. Model validation across a range of stresses and pore pressures shows excellent agreement with experimental data, confirming its predictive robustness. These findings reveal fundamental differences between sorptive and non-sorptive gas effects on shale time-dependent deformation and underscore the need to account for adsorption and damage mechanisms in predictive frameworks, with direct implications for unconventional hydrocarbon production, CO 2 sequestration, and the long-term stability of geological storage sites. • Sorptive gas (CO 2 ) significantly enhances shale creep through gas adsorption and damage. • Non-sorptive gas (He) produces negligible creep effects. • A new sorption-damage-creep model integrates gas adsorption, damage, and time-dependent deformation. • Model validation shows strong agreement with experimental results across various stress and pore pressure ranges. • Study provides a mechanistic and predictive framework for unconventional gas and CO 2 storage projects.

Transient magnetohydrodynamic flow over a rotating vertical porous surface incorporating thermal radiation, hall and ion-slip effects: Using finite element method

Comparisons of the rheological, tribological and sensory properties of sodium alginate with commercial thickeners at different IDDSI levels for dysphagia management.

Exploring molecular-level rolling friction based on cyclodextrins for lubrication.

Parameterization of bottom friction coefficient depending on sediment types and its application in tide simulation in the Eastern China Marginal Seas

Mechanisms of astringency modulation: How sugars and organic acids modulate epigallocatechin gallate astringency in new-style fruit tea.

The present study examines the magnetohydrodynamics (MHD) flow of a ternary hybrid nanofluid, comprised of titanium oxide, zinc oxide, and gold nanoparticles dispersed in a water-based fluid, over a curvilinear catalytic surface within a porous medium. The model integrates volumetric and surface nonthermal plasma heating with species generation. The Joseph slip conditions are implemented to characterize the tangential partial slip behavior. The governing partial differential equations are reduced to a system of nonlinear, coupled ordinary differential equations for analysis. Subsequently, the Galerkin weighted residual method is employed to solve the resulting system of equations. The friction coefficients compared to the existing literature demonstrate an agreement. The skin friction coefficient, Nusselt number, and Sherwood number converge to 0.202419, -1.48261, and -1.00, respectively, for different trial numbers. Volumetric and surface nonthermal plasma heating have been observed to enhance the Nusselt number, whereas the species generation parameter correspondingly increases the Sherwood number. The magnetic parameter diminishes fluid velocity and enhances energy and species concentrations, while the isotherm contours exhibit a pronounced elliptic configuration, thereby illustrating the fluid's thermal maximum. These findings indicate that the magnetic parameter can be employed to guide the fluid, thereby facilitating the localization and subsequent removal of charged impurities within the system. Furthermore, the nonthermal plasma parameters not only elevate the fluid's temperature but also exhibit a propensity to enhance heat and mass transfer between the fluid and the curved catalytic surface.