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General medicine general surgery, Médecine et chirurgie générales, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure electronique, proprietes electriques, magnetiques et optiques, Condensed matter: electronic structure, electrical, magnetic, and optical properties, Structure électronique et propriétés électriques des surfaces, interfaces, couches minces et structures de basse dimensionnalité, Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures, Etats électroniques de surface et d'interface, Surface and interface electron states, Excitations collectives (incluant excitons, polarons, plasmons et autres excitations de densité de charge), Collective excitations (including excitons, polarons, plasmons and other charge-density excitations), Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Science des matériaux, Materials science, Nanomatériaux et nanostructures : fabrication et caractèrisation, Nanoscale materials and structures: fabrication and characterization, Matériaux nanocristallins, Nanocrystalline materials, Champ température, Temperature distribution, Dispersion, Dispersions, Etude expérimentale, Experimental study, Nanomatériau, Nanostructured materials, Nanoparticule, Nanoparticles, Nanosphère, Nanosphere, Nanosfera, Or, Gold, Plasmon, Plasmons, Résultat expérimental, Experimental result, Resultado experimental, Source lumière, Light sources, Traitement surface, Surface treatments, Traitement thermique, Heat treatments, 7320M, and 8107B

In this experimental study, a filtered white light is used to induce heating in water-based dispersions of 20 nm diameter gold nanospheres (GNSs)—enabling a low-cost form of plasmonic photothermal heating. The resulting temperature fields were measured using an infrared (IR) camera. The effect of incident radiative flux (ranging from 0.38 to 0.77W-cm-2) and particle concentration (ranging from 0.25-1.0 × 1013 particles per mL) on the solution's temperature were investigated. The experimental results indicate that surface heat treatments via GNSs can be achieved through complementary tuning of GNS solutions and filtered light.

Mechanical engineering, Génie mécanique, Mechanics acoustics, Mécanique et acoustique, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Science des matériaux, Materials science, Traitements de surface, Surface treatments, Contrainte compression, Compressive stress, Tensión compresión, Déformation plastique, Plastic deformation, Déformation superficielle, Surface deformation, Deformación superficial, Effet pression, Pressure effects, Gouttelette, Droplets, Grenaillage, Shot peening, Haute pression, High pressure, Jet eau, Water jet, Chorro agua, Microdureté, Microhardness, Microstructure, Profilométrie, Profilometry, Perfilometría, Rugosité, Roughness, Traitement surface, Surface treatments, Grenaillage choc laser, and Laser shock peening

An experimental study was conducted to explore the surface preparation as well as the effects of high-pressure waterjet peening at 600 MPa on the surface integrity and finish of metals. The concept of larger droplet size and multiple droplet impacts resulting from an ultra-high-pressure waterjet was used to explore and develop the peening process. A combination of microstructure analysis, microhardness measurements, and profilometry were used in determining the depth of plastic deformation and surface finish that result from the surface treatment process. It was found that waterjet peening at 600 MPa induces plastic deformation to greater depths in the subsurface layer of metals than laser shock peening. The degree of plastic deformation and the state of the material surface were found to be strongly dependent on the peening conditions and desired surface roughness. Based on these first investigation results, water peening at 600 MPa may serve as a new method for introducing compressive residual stresses in engineering components.

Control theory, operational research, Automatique, recherche opérationnelle, Mechanical engineering, Génie mécanique, Mechanics acoustics, Mécanique et acoustique, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Genie mecanique. Construction mecanique, Mechanical engineering. Machine design, Transmissions, Drives, Engrenages, Gears, Accouplement arbre, Shaft coupling, Acoplamiento árbol, Analyse régression, Regression analysis, Análisis regresión, Coefficient frottement, Friction coefficient, Coeficiente roce, Condition opératoire, Operating conditions, Condición operatoria, Denture engrenage, Gear tooth, Dentado engranaje, Distribution charge, Load distribution, Distribución carga, Engrenage, Gear, Engranaje, Etat surface, Surface conditions, Estado superficie, Fluide non newtonien, Non Newtonian fluid, Fluido no-newtoniano, Frottement, Friction, Frotamiento, Lubrifiant, Lubricant, Lubricante, Lubrification élastohydrodynamique, Elastohydrodynamic lubrication, Lubrificación elastohidrodinámica, Modélisation, Modeling, Modelización, Propriété mécanique, Mechanical properties, Propiedad mecánica, Régression multiple, Multiple regression, Regresión múltiple, Traitement surface, Surface treatment, and Tratamiento superficie

A computational model is proposed for the prediction of friction-related mechanical efficiency losses of parallel-axis gear pairs. The model incorporates a gear load distribution model, a friction model, and a mechanical efficiency formulation to predict the instantaneous mechanical efficiency of a gear pair under typical operating, surface, and lubrication conditions. The friction model uses a new friction coefficient formula obtained by using a validated non-Newtonian thermal elastohydrodynamic lubrication (EHL) model in conjunction with a multiple linear regression analysis. The load and friction coefficient, distribution predictions are used to compute instantaneous torque/ power losses and the mechanical efficiency of a gear pair at any given rotational position. Efficiency measurements from gear pairs having various gear designs and surface treatments are compared to model predictions. Mechanical efficiency predictions are shown to be within 0.1% of the measured values, indicating that the proposed efficiency model is accurate. Results of a parametric study are presented at the end to highlight the influence of key basic gear geometric parameters, tooth modifications, operating conditions, surface finish, and lubricant properties on mechanical efficiency losses.

Mechanical engineering, Génie mécanique, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Genie chimique, Chemical engineering, Fluidisation, Fluidization, Metaux. Metallurgie, Metals. Metallurgy, Transformation de matériaux métalliques, Production techniques, Usinage, Cutting, Usinage avec enlèvement de copeaux, Machining. Machinability, Genie mecanique. Construction mecanique, Mechanical engineering. Machine design, Généralités, General, Métrologie industrielle. Contrôle, Industrial metrology. Testing, Abrasif, Abrasives, Abrasivo, Schleifmittel, Alliage base nickel, Nickel base alloys, Circularité, Roundness, Circularidad, Condition opératoire, Operating conditions, Condición operatoria, Contrainte résiduelle, Residual stress, Tensión residual, Eigenspannung, Effet dimensionnel, Size effect, Efecto dimensional, Groesseneffekt, Etat surface, Surface conditions, Estado superficie, Oberflaechenzustand, Finissage surface, Surface finishing, Grosseur grain, Grain size, Grosor grano, Korngroesse, Inconel, Lissage, Smoothing, Alisamiento, Lit fluidisé, Fluidized bed, Lecho fluidizado, Profondeur pénétration, Penetration depth, Profundidad penetración, Rectification intérieure, Internal grinding, Rectificación interior, Innenschleifen, Rugosité, Roughness, Rugosidad, Rauhigkeit, Surface contact, Contact surface, Superficie contacto, Surface rugueuse, Rough surface, Superficie rugosa, Rauhe Oberflaeche, Traitement surface, Surface treatment, Tratamiento superficie, Oberflaechenbehandlung, Tube métallique, Metal tube, Tubo metálico, Usinage abrasif, Abrasive machining, Maquinado abrasivo, Usinage jet abrasif, Abrasive jet machining, Maquinado chorro abrasivo, Fluessigkeitsstrahlbearbeiten, Inconel 718, finishing characteristics, fluidized bed assisted abrasive finishing, internal finishing, residual stress, roundness, and surface roughness

The relatively new technique of fluidized bed assisted abrasive jet machining (FB-AJM) is applied to finishing the inner surfaces of tubular Inconel 718 components. The effects of abrasive size, jet pressure, and machining cycle were evaluated, and the behavior of abrasive cutting edges acting against the surface during the process to remove material is accounted for. The finished surface was found to be highly dependent on jet pressure because it affects the abrasive contact against the surface as well as the finishing force acting on the abrasive, on the abrasive grain size, which controls the depth of cut, and on machining cycle, which controls the interaction time between the abrasives and the surface being finished. By altering these conditions, this process achieves surface roughness (Ra) as fine as 0.1 μm and imparts minimal additional residual stress on the surface. This study also reveals the mechanisms that determine the smoothing of the inner surface of Inconel 718 tubes and improve the form accuracy, i.e., the internal roundness of the Inconel 718 tube.

Mechanical engineering, Génie mécanique, Mechanics acoustics, Mécanique et acoustique, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Domaines classiques de la physique (y compris les applications), Fundamental areas of phenomenology (including applications), Acoustique, Acoustics, Acoustique sous-marine, Underwater sound, Mécanique des solides, Solid mechanics, Mécanique des structures et des milieux continus, Structural and continuum mechanics, Elasticité statique (thermoélasticité...), Static elasticity (thermoelasticity...), Inélasticité (thermoplasticité, viscoplasticité...), Inelasticity (thermoplasticity, viscoplasticity...), Mécanique des fluides, Fluid dynamics, Ecoulements non homogènes, Nonhomogeneous flows, Gouttes et bulles, Drops and bubbles, Aluminium alliage, Aluminium alloy, Aluminio aleación, Bulle cavitation, Cavitation bubble, Burbuja cavitación, Cavitation, Cavitación, Contrainte résiduelle, Residual stress, Tensión residual, Contrainte superficielle, Surface stresses, Diffraction RX, X ray diffraction, Difracción RX, Déformation superficielle, Surface deformation, Deformación superficial, Gouttelette, Droplet, Gotita, Grande vitesse, High speed, Gran velocidad, Grenaillage, Shot peening, Granalla, Interaction, Interacción, Inélasticité, Inelasticity, Inelasticidad, Limite élasticité, Yield strength, Límite elasticidad, Martelage, Peening, Martillado, Nuage, Clouds, Nube, Plasticité, Plasticity, Plasticidad, Surface lisse, Smooth surface, Superficie lisa, Traitement surface, Surface treatment, Tratamiento superficie, cavitation jet peening, hardening, residual stress, and surface morphology

A new surface modification process was developed to introduce compressive residual stresses at the surface of components. In this process, instead of oil droplets a high-velocity cavitation jet (cloud of oil bubbles) impinges on the surface of the component to be peened. The impact pressure generated during implosion of cavitation bubbles causes severe plastic deformation at the surface. Consequently, beneficial compressive stresses are developed at the surface. In order to find the potential of this process, aluminum alloy AA6063-T6 specimens were peened at a constant cavitation number with various nozzle-traveling velocities. Residual stress induced by oil jet cavitation peening was measured using X-ray diffraction. Oil cavitation jet peening results in a smooth and hard surface. The developed compressive residual stresses at the peened surface are about 52%, 42%, and 35% of yield strength in samples for peened at nozzle traveling velocities of 0.05 mm/s, 0.10 mm/s, and 0.15 mm/s, respectively.

Mechanical engineering, Génie mécanique, Mechanics acoustics, Mécanique et acoustique, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Domaines classiques de la physique (y compris les applications), Fundamental areas of phenomenology (including applications), Mécanique des solides, Solid mechanics, Mécanique des structures et des milieux continus, Structural and continuum mechanics, Mécanique de la rupture (fissure, fatigue, endommagement...), Fracture mechanics (crack, fatigue, damage...), Sciences appliquees, Applied sciences, Genie mecanique. Construction mecanique, Mechanical engineering. Machine design, Organes de machines, Machine components, Frottement, usure, lubrification, Friction, wear, lubrication, Alliage surface, Surface alloying, Aleación superficie, Bore, Boron, Boro, Boruration, Boriding, Boruración, Contact roulant, Rolling contact, Contacto rodante, Décharge luminescente, Glow discharge, Descarga luminiscente, Essai usure, Wear test, Prueba al desgaste, Etude expérimentale, Experimental study, Estudio experimental, Fer, Iron, Hierro, Frottement glissement, Sliding friction, Frotamiento deslizamiento, Frottement sec, Dry friction, Frotamiento seco, Machine mouvement alternatif, Reciprocating movement machine, Máquina movimiento alterno, Microscopie force atomique, Atomic force microscopy, Microscopía fuerza atómica, Microscopie électronique balayage, Scanning electron microscopy, Microscopía electrónica barrido, Métrologie surface, Surface metrology, Metrología superficie, Optimisation, Optimization, Optimización, Orientation cristalline, Crystal orientation, Orientación cristalina, Pureté, Purity, Pureza, Radiofréquence, Radiofrequency, Radiofrecuencia, Revêtement diffusion, Diffusion coatings, Résistance usure, Wear resistance, Resistencia al desgaste, Spectrométrie émission, Emission spectrometry, Espectrometría emisión, Traitement surface, Surface treatment, Tratamiento superficie, Tribologie, Tribology, Tribología, Usure, Wear, Desgaste, Boronisation, Boronization, Boronización, boronized surface coatings, friction, growth kinetics, pseudo-rolling, sliding, and wear

This research investigates the morphological nature and tribological behavior of boronized pure iron using experiments combined with theoretical analysis. Samples studied were 99.97% purity iron boronized for 4 h at 800°C, 875°C and 950°C, respectively. Diffusion of the borided layer was analyzed by measuring the extent of penetration of the boride to sublayers as a function of boriding time and temperature. The distribution of alloying elements from surface to interior was determined by using rf-glow discharge optical emission spectrometry. It was found that boron concentrated in the layer and the diffusion of B atoms was deeper than the layer itself In tribological tests, friction and wear behavior under dry rolling with sliding (pseudo-rolling) and dry pure sliding conditions was investigated. The wear experiments were conducted using a modified linear reciprocating tribometer A scanning electron microscope and atomic force microscope were used for worn surface characterization. It was found that boronizing at 875°C exhibited the best wear resistance among the samples tested. Higher wear resistance was correlated with growth of boride crystals along stronger (002) orientation. Surface grain size distribution after the boriding process was identified as an important factor for wear resistance. Different fracture and wear modes were investigated. Analysis of the wear debris gave an insight into the operative wear mechanisms. This research is beneficial in optimizing the parameters of the boronizing process to achieve better wear resistance under different contact modes.

Mechanical engineering, Génie mécanique, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Domaines classiques de la physique (y compris les applications), Fundamental areas of phenomenology (including applications), Mécanique des solides, Solid mechanics, Mécanique des structures et des milieux continus, Structural and continuum mechanics, Mécanique de la rupture (fissure, fatigue, endommagement...), Fracture mechanics (crack, fatigue, damage...), Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Science des matériaux, Materials science, Traitements de surface, Surface treatments, Sciences appliquees, Applied sciences, Genie mecanique. Construction mecanique, Mechanical engineering. Machine design, Acier inoxydable austénitique, Austenitic stainless steel, Acero inoxidable austenítico, Acier mi-dur, Medium carbon steel, Acero semi duro, Contrainte compression, Compressive stress, Tensión compresión, Contrainte résiduelle, Residual stress, Tensión residual, Durée vie fatigue, Fatigue life, Longevidad fatiga, Eprouvette essai, Test bar, Probeta ensayo, Etat surface, Surface conditions, Estado superficie, Fatigue contact, Fretting fatigue, Fatiga contacto, Grenaillage, Shot peening, Granalla, Haute pression, High pressure, Alta presión, Jet, Mesure optique, Optical measurement, Medida óptica, Température ambiante, Room temperature, Temperatura ambiente, Traitement surface, Surface treatment, Tratamiento superficie, fatigue performance, oil jet peening, residual stress, and surface topography

Introduction of compressive residual stresses on the fatigue-loaded components is one of the techniques followed to improve the fatigue life of industrial components. Oil jet peening is a surface modification process for the introduction of compressive residual stresses. A high-pressure oil jet is made to impinge on the surface to be peened. Preliminary studies were carried out on the medium carbon steel at the oil pressure of 50 MPa. The compressive residual stress induced on the surface of unpeened and oil jet-peened AISI 1040 steel was 21 MPa and 200 MPa, respectively. Fully reversed cantilever bending fatigue behaviors of medium carbon steel in both under peened and unpeened conditions were evaluated at room temperature. Oil jet-peened specimens exhibited superior fatigue performance compared to the unpeened specimens. Fractographical analyses were carried out for specimens broken at several tested stress levels using optical microscope.

Mechanical engineering, Génie mécanique, Mechanics acoustics, Mécanique et acoustique, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Genie mecanique. Construction mecanique, Mechanical engineering. Machine design, Organes de machines, Machine components, Frottement, usure, lubrification, Friction, wear, lubrication, Joints et garnitures d'étanchéité, Seals and gaskets, Condition stationnaire, Stationary condition, Condición estacionaria, Densité élevée, High density, Densidad elevada, Equation Reynolds, Reynolds equation, Ecuación Reynolds, Etat surface, Surface conditions, Estado superficie, Fluide compressible, Compressible fluid, Fluido compresible, Fluide newtonien, Newtonian fluid, Fluido newtoniano, Fusion laser, Laser fusion, Fusión láser, Fusion surface, Surface melting, Fusión superficie, Haute pression, High pressure, Alta presión, Jeu mécanique, Mechanical clearance, Juego mecánico, Joint gaz, Gas seal, Junta gas, Joint mécanique, Mechanical seal, Junta mecánica, Joint rotatif, Rotary seal, Junta rotativa, Joint étanchéité, Seal, Soldadura estanqueidad, Lubrifiant gazeux, Gaseous lubricant, Lubricante gaseoso, Lubrification hydrostatique, Hydrostatic lubrication, Lubrificación hidrostática, Modélisation, Modeling, Modelización, Optimisation, Optimization, Optimización, Perte charge, Pressure drop, Pérdida carga, Pression hydrostatique, Hydrostatic pressure, Presión hidrostática, Texturation, Texturación, Traitement par laser, Laser assisted processing, Traitement surface, Surface treatment, Tratamiento superficie, Tribologie, Tribology, Tribología, design efficiency parameter, film stiffness, hydrostatic seal, and laser surface texturing

Microdimples generated by laser surface texturing (LST) can be used to enhance performance in hydrostatic gas-lubricated mechanical seals. This is achieved by applying microdimples with high area density over a certain portion of the sealing dam width adjacent to the high-pressure side, leaving the remaining portion untextured. The textured portion provides an equivalent larger gap that results in converging clearance in the direction of pressure drop and hence, hydrostatic pressure buildup, similar to that of a radial step seal. A mathematical model based on the solution of the Reynolds equation for compressible Newtonian fluid in a narrow gap between two nominally parallel stationary surfaces is developed. A detailed dimensionless analysis of the texturing parameters is performed to achieve maximum gas film stiffness with minimum gas leakage.

Energy, Énergie, Mechanical engineering, Génie mécanique, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Domaines classiques de la physique (y compris les applications), Fundamental areas of phenomenology (including applications), Mécanique des solides, Solid mechanics, Mécanique des structures et des milieux continus, Structural and continuum mechanics, Mécanique de la rupture (fissure, fatigue, endommagement...), Fracture mechanics (crack, fatigue, damage...), Sciences appliquees, Applied sciences, Genie mecanique. Construction mecanique, Mechanical engineering. Machine design, Constructions métalliques, Steel design, Réservoirs métalliques et enceintes sous pression; chaudronnerie, Steel tanks and pressure vessels; boiler manufacturing, Acier ferritique, Ferritic steel, Acero ferrítico, Acier inoxydable, Stainless steel, Acero inoxidable, Analyse contrainte, Stress analysis, Análisis tensión, Arrêt fissure, Crack arrest, Parada fisura, Assemblage soudé, Welded joint, Ensamblaje soldado, Charge thermique, Thermal load, Carga térmica, Contrainte compression, Compressive stress, Tensión compresión, Contrainte résiduelle, Residual stress, Tensión residual, Contrainte traction, Tensile stress, Tensión traccíon, Cycle thermique, Thermal cycle, Ciclo térmico, Durcissement déformation, Strain hardening, Endurecimiento deformación, Durée vie fatigue, Fatigue life, Longevidad fatiga, Essai fatigue, Fatigue test, Ensayo fatiga, Essai matériau, Material testing, Control material, Fatigue thermique, Thermal fatigue, Fatiga térmica, Fissure superficielle, Surface crack, Fisura superficial, Propriété thermomécanique, Thermomechanical properties, Propriedad termomecánica, Réseau fissure, Crack array, Red fisura, Traitement surface, Surface treatment, Tratamiento superficie, Traitement thermique, Heat treatment, Tratamiento térmico, crack arrest, crazing, shot peening, stainless steel, thermal fatigue, and weld residual stress

The aim of this paper is to improve the understanding of high cycle thermal fatigue crazing observed in some areas of residual heat removal (RHR) systems made of 304L stainless steel in PWR nuclear plants. High cycle thermal crazing and the absence of crazing under purely mechanical loading are explained through the arrest of cracks initiated at the surface in the thickness of the component for thermal fatigue. This arrest is due to high stress gradients in the case of thermal loading due to the high frequency of the thermal load. It is shown that close to the weld, the crack network configuration is related to the tensile weld residual stress field in accordance with the detrimental effect of tensile mean stress on fatigue life. However, these results are in apparent contradiction with the material uniaxial fatigue tests, where a beneficial effect of tensile mean stress is observed in load-controlled fatigue tests. Moreover, it is shown that near the weld, the absence of a crack network is related to the compressive weld residual stress field in accordance with the beneficial effect of compressive mean stress on fatigue life. This result is however, in apparent contradiction with the observation of crazing far from the weld under a highly compressive stress. These contradictions may be explained by the detrimental effect of prehardening in strain control and the beneficial effect of prehardening in stress control for stainless steels. From these results it is concluded that shot peening which is usually considered to be beneficial for ferritic steel may be detrimental in high cycle thermal fatigue for stainless steels. It may also be concluded that in high cycle thermal fatigue of stainless steel, improvement of fatigue life would be possible with heat treatment by reduction of strain-hardening rather than with shot peening.

Mechanical engineering, Génie mécanique, Mechanics acoustics, Mécanique et acoustique, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Domaines classiques de la physique (y compris les applications), Fundamental areas of phenomenology (including applications), Mécanique des solides, Solid mechanics, Mécanique des structures et des milieux continus, Structural and continuum mechanics, Contact mécanique (frottement...), Mechanical contact (friction...), Sciences appliquees, Applied sciences, Genie mecanique. Construction mecanique, Mechanical engineering. Machine design, Organes de machines, Machine components, Frottement, usure, lubrification, Friction, wear, lubrication, Acier roulement, Ball bearing steel, Acero rodamiento de bolas, Approche déterministe, Deterministic approach, Enfoque determinista, Contact ponctuel, Point contact, Contacto puntual, Contrainte cisaillement, Shear stress, Tensión cizallamiento, Contrainte contact, Contact stress, Tensión contacto, Effet Stribeck, Stribeck effect, Efecto Stribeck, Essai frottement, Friction test, Prueba frotamiento, Essai matériau, Material testing, Control material, Etude expérimentale, Experimental study, Estudio experimental, Film lubrifiant, Lubricating film, Película lubricante, Frottement glissement, Sliding friction, Frotamiento deslizamiento, Localisation, Localization, Localización, Lubrification limite, Boundary lubrication, Lubrificación frontera, Lubrification mixte, Mixed lubrication, Lubrificación mixta, Lubrification élastohydrodynamique, Elastohydrodynamic lubrication, Lubrificación elastohidrodinámica, Modélisation, Modeling, Modelización, Pression contact, Contact pressure, Presión contacto, Rhéologie, Rheology, Reología, Rugosité, Roughness, Rugosidad, Surface contact, Contact surface, Superficie contacto, Surface rugueuse, Rough surface, Superficie rugosa, Traitement surface, Surface treatment, Tratamiento superficie, Tribologie, Tribology, Tribología, Vitesse critique, Critical speed, Velocidad crítica, mixed lubrication, numerical simulations, roughness effects, and sliding friction

This paper presents a numerical approach to simulate sliding friction between engineering surfaces with 3D roughness in point contacts. The numerical approach is developed on the basis of the deterministic solutions of mixed lubrication, which is able to predict the locations where the asperity contacts occur, and the pressure distribution over both lubrication and contact areas. If the friction coefficients over the contacting asperities have been determined, total friction force between the surfaces can be calculated by summing up the two components, i.e., the boundary friction contributed by contacting asperities and the shear stress in hydrodynamic regions. The frictions from asperity contact were determined in terms of a limiting shear stress or shear strength of boundary films while the fluid shear stress in the lubrication areas was calculated using different rheology models for the lubricant, in order to find which one would be more reliable in predicting fluid tractions. The simulations covered the entire lubrication, regime, including full-film Elastohydrodynamic Lubrication (EHL), mixed lubrication, and boundary lubrication. The results, when being plotted as a function of sliding velocity, give a Stribeck-type friction curve. This provides an opportunity to study friction change during the transition of lubrication conditions and to compare friction performance on different rough surfaces, which is of great value in engineering practice. Experiments were conducted on a commercial test device-universal material tester (UMT) to measure friction at a fixed load but different sliding velocities in reciprocal or rotary motions. The results also give rise to the Stribeck friction curves for different rough surfaces, which are to be compared with the results from simulations. The samples were prepared with typical machined surfaces in different roughness heights and textures, and in point contacts with steel ball. Results show that there is a general agreement between the experiments and simulations. It is found that surface features, such as roughness amplitude and patterns, may have a significant effect on the critical speed of transition from hydrodynamic to mixed lubrication. In the regime of mixed lubrication, rougher samples would give rise to a higher friction if the operation conditions are the same.

Mechanical engineering, Génie mécanique, Mechanics acoustics, Mécanique et acoustique, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Domaines classiques de la physique (y compris les applications), Fundamental areas of phenomenology (including applications), Mécanique des solides, Solid mechanics, Mécanique des structures et des milieux continus, Structural and continuum mechanics, Mécanique de la rupture (fissure, fatigue, endommagement...), Fracture mechanics (crack, fatigue, damage...), Sciences appliquees, Applied sciences, Genie mecanique. Construction mecanique, Mechanical engineering. Machine design, Organes de machines, Machine components, Frottement, usure, lubrification, Friction, wear, lubrication, Approche déterministe, Deterministic approach, Enfoque determinista, Contact glissant, Sliding contact, Contacto deslizante, Contact ponctuel, Point contact, Contacto puntual, Déformation superficielle, Surface deformation, Deformación superficial, Epaisseur couche, Layer thickness, Espesor capa, Etat surface, Surface conditions, Estado superficie, Film lubrifiant, Lubricating film, Película lubricante, Localisation, Localization, Localización, Lubrification mixte, Mixed lubrication, Lubrificación mixta, Lubrification élastohydrodynamique, Elastohydrodynamic lubrication, Lubrificación elastohidrodinámica, Maintenance, Mantenimiento, Modèle mixte, Mixed model, Modelo mixto, Modélisation, Modeling, Modelización, Pression contact, Contact pressure, Presión contacto, Rugosité, Roughness, Rugosidad, Rupture, Ruptura, Surface contact, Contact surface, Superficie contacto, Surface rugueuse, Rough surface, Superficie rugosa, Traitement surface, Surface treatment, Tratamiento superficie, Tribologie, Tribology, Tribología, Usure glissement, Sliding wear, Desgaste deslizamiento, Vitesse usure, Wear rate, Velocidad desgaste, mixed EHL simulation, and sliding wear

Sliding wear is a significant surface failure mode in many mechanical components. The magnitude of changes in surface topography due to wear may be comparable to or larger than the original surface roughness and elastic deformation. However, wear has rarely been incorporated into the numerical models used as predictive tools in engineering practice. This paper presents a numerical approach to simulate the wear process based on the deterministic mixed elastohydrodynamic lubrication (EHL) model developed and modified by Zhu and Hu (2001, Tribal. Trans., 44, pp. 383-398). It is assumed that wear takes place at locations where the surfaces are in direct contact, and the wear rate at those local contact spots is proportional to the relative sliding speed, the local contact pressure, and inversely proportional to the hardness of the surface. At each simulation cycle, the distributions of lubricant film thickness and contact pressure are calculated by using the mixed EHL model. The material removal at each contact location is evaluated and the surface topography modified correspondingly. The renewed surface topography is then used for the next cycle. The model is formulated such that any mathematically expressed wear law can be implemented, and therefore, the simulation can be applied to a wide variety of engineering applications.