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Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Fatigue, Acier non allié, Carbon steel, Acero no aliado, Unlegierter Stahl, Fatigue, Fatiga, Ermuedung, Fissure fatigue, Fatigue crack, Fisura fatiga, Ermuedungsriss, Fractographie, Fractography, Fractografía, Fraktographie, Microstructure, Microestructura, Mikrogefuege, Mode déformation, Deformation mode, Modo deformación, Mécanisme, Mechanism, Mecanismo, Propagation fissure, Crack propagation, Propagación fisura, Rissausbreitung, Propriété mécanique, Mechanical properties, Propiedad mecánica, Seuil fatigue, Fatigue threshold, Umbral fatiga, crack branching, crack growth induced microstructure change, factory- roof, mode II fatigue crack growth, mode III fatigue crack growth, and threshold stress intensity factor range

The fatigue crack growth behaviour of 0.47% carbon steel was studied under mode II and III loadings. Mode II fatigue crack growth tests were carried out using specially designed double cantilever (DC) type specimens in order to measure the mode II threshold stress intensity factor range, ΔKIIth. The relationship ΔKIIth >ΔKIth caused crack branching from mode II to I after a crack reached the mode II threshold. Torsion fatigue tests on circumferentially cracked specimens were carried out to study the mechanisms of both mode III crack growth and of the formation of the factory-roof crack surface morphology. A change in microstructure occurred at a crack tip during crack growth in both node II and mode III shear cracks. It is presumed that the crack growth mechanisms in mode II and in mode III are essentially the same. Detailed fractographic investigation showed that factory-roofs were formed by crack branching into mode I. Crack branching started from small semi-elliptical cracks nucleated by shear at the tip of the original circumferential crack.

Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Fatigue, Addition silicium, Silicon addition, Adición silicio, Siliciumzusatz, Alliage base titane, Titanium base alloys, Alliage quaternaire, Quaternary alloys, Alliage ternaire, Ternary alloy, Aleación ternaria, Aluminium alliage, Aluminium alloy, Aluminio aleación, Aluminiumlegierung, Chrome alliage, Chromium alloy, Cromo aleación, Chromlegierung, Essai Charpy, Charpy test, Ensayo Charpy, Etude expérimentale, Experimental study, Estudio experimental, Experimentelle Untersuchung, Fatigue plastique, Plastic fatigue, Fatiga plástica, Fissure fatigue, Fatigue crack, Fisura fatiga, Ermuedungsriss, Fractographie, Fractography, Fractografía, Fraktographie, Microstructure, Microestructura, Mikrogefuege, Molybdène alliage, Molybdenum alloy, Molibdeno aleación, Molybdaenlegierung, Mécanique rupture, Fracture mechanics, Mecánica ruptura, Bruchmechanik, Propriété mécanique, Mechanical properties, Propiedad mecánica, Synergie, Synergism, Sinergia, Al Cr Mo Ti, Al Mo Ti, Alliage Ti89Al6Mo3Cr2, Alliage Ti91Al6Mo3, Compresseur, Disque, Fatigue, Forme onde, Moteur, Charpy-tests, compressor disks, facetted pattern, fatigue cracks, hold time, striations, synergetics, and titanium alloys

Microstructural variations produced from manufacturing processes and their influence on fatigue crack growth in titanium disks were investigated. Charpy-tests on titanium disk material were performed and materials with fracture energy values in the range of 3. 8-19. 1 J/ cm2 were selected for tests under cyclic loads. Results of (Charpy-tests were compared with fractographic features related to fatigue crack growth in Ti-6A1-3Mo-0.4Si and Tri-6A1-3Mo-2Cr alloys with a two-phase (α+β) lamellar structure under various cyclic waveforms using specimens made from compressor disks. The material sensitivity to cyclic load waveform can be seen for in-service disks using a criteria based on fracture energy values determined in (Charpy-tests. A difference in fatigue crack growth periods of2.5 times was discovered for specimens made from the disk with a filament type microstructure and the mainly globular two-phase structure of the Ti-6Al-3Mo-0.4Si alloy. The shorter crack growth period correlated with the mainly facetted pattern formation with local zones of fatigue striations when fatigue crack growth is along the planes of the filaments. Fatigue striations are the major fracture surface relief when crack growth occurs in the perpendicular direction to the plane of the filaments. A quantitative fractographic method for estimating the crack growth period for in-service failed disks was performed for the case of crack development along planes of such microstructural filaments created during the manufacturing process. Specimen tests involving a hold-time in the cyclic loads are recommended for in-service accepted titanium disks using a criteria based on the fracture energy value. Selection of disks based on these criteria conn indicate a material sensitivity to cyclic load waveforms.

Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Elasticité. Plasticité, Elasticity. Plasticity, Alliage base aluminium, Aluminium base alloys, Alumine, Alumina, Alúmina, Tonerde, Bande déformation, Deformation band, Banda deformación, Deformationsband, Composite matrice métallique, Metal matrix composite, Compuesto matriz metalico, Déformation plastique, Plastic deformation, Deformación plástica, Plastische Verformung, Etude expérimentale, Experimental study, Estudio experimental, Experimentelle Untersuchung, Laminage à froid, Cold rolling, Laminado en frío, Kaltwalzen, Métal renforcé dispersion, Dispersion strengthened metal, Metal reforzado dispersión, Dispersionsgehaertetes Metall, Propriété mécanique, Mechanical properties, Propiedad mecánica, Recuit, Annealing, Recocido, Gluehen, Relation contrainte déformation, Stress strain relation, Relación tensión deformación, Traitement thermique, Heat treatment, Tratamiento térmico, Waermebehandlung, Composite partciule Al)50 Al2O3, Déformation, Inclusion non métallique, Matériau composite, Microstructure, composites, physical mesomechanics, plastic deformation band, and strain localization

Using a television optical TOMSC system, regular features of localization of macroplastic deformation are studied in composite aluminum-based materials with. hard inclusions ofAl203 under tension. Before investigation, the specimens are subjected to cold rolling, tempering for 30 min at 500°C with subsequent cooling in air, and annealing at 550 C during 2 h with subsequent cooling in furnace. It is shown that the tempered and annealed alloys exhibit mobile centers of active macrolocalization long before the formation of a stationary neck preceding material fracture. Physical mesomechanics, relying on the concepts of the leading role of different-scale stress concentrators that relax and develop in a loaded heterogeneous material, is capable of providing a qualitative description of macrolocalization development.

Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Rupture, Fractures, Dureté, Hardness, Dureza, Haerte, Déformation plastique, Plastic deformation, Deformación plástica, Plastische Verformung, Dépôt faisceau électronique, Electron beam deposition, Etude expérimentale, Experimental study, Estudio experimental, Experimentelle Untersuchung, Fracture, Fractura, Interface, Interfase, Grenzflaeche, Matériau composite, Composite material, Material compuesto, Verbundwerkstoff, Microstructure, Microestructura, Mikrogefuege, Mécanique rupture, Fracture mechanics, Mecánica ruptura, Bruchmechanik, Propriété mécanique, Mechanical properties, Propiedad mecánica, Revêtement composite, Composite coating, Revestimiento compuesto, Faisceau électronique, Rupture, composite coating, electron beam, interface, and physical mesomechanics

Electron-beam deposition (EBD) is an advanced technique intended for the formation of protective coatings that exhibit high strength and wean and fatigue resistance. The investigation of the structure of coated materials and the development of mesoscale plastic deformation shows that these properties depend heavily on EBD modes. It is proposed that the latter can be optimized by: (i) choosing the electron-beam parameters that ensure a uniform structure of the coating, appropriate width and proper structure of the transient zone, (ii) the trial-and-error method of selecting such deposited powder composition that ensure high strength properties, and (iii) mechanical test aimed at distinguishing the coatings whose performance has been advantageously increased by EBD.

Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Propriétés mécaniques et acoustiques de l'état condensé, Mechanical and acoustical properties of condensed matter, Propriétés mécaniques des solides, Mechanical properties of solids, Fatigue, fragilisation, rupture et fissures, Fatigue, brittleness, fracture, and cracks, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Amorçage fissure, Crack formation, Etude théorique, Theoretical study, Fracture, Fractures, Mécanique rupture, Fracture mechanics, Propagation fissure, Crack propagation, Propriété mécanique, Mechanical properties, Résistance mécanique, Mechanical strength, Rupture, crack growth initiation, dynamic strength, incubation time, materials testing, solid particle erosion, and spalling fracture

Discrete features of the dynamics of fracture of solids are analyzed. The problem of modeling of some of the specific effects of brittle fracture in the high loading rate conditions is discussed. An approach based on the system of fixed material constants describing macro-strength properties of the material is considered. New principles of material testing are analyzed. The corresponding incubation time criterion allows one to manage without the a priori given rate dependences of dynamic strength and fracture toughness. An application of the incubation time criterion to the problem of erosion is considered.

Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Rupture, Fractures, Analyse contrainte, Stress analysis, Análisis tensión, Spannungsanalyse, Contrainte contact, Contact stress, Tensión contacto, Contrainte interne, Internal stress, Tensión interna, Etude théorique, Theoretical study, Estudio teórico, Theoretische Untersuchung, Fracture, Fractura, Interaction contact, Contact interaction, Interacción contacto, Matrice emboutissage, Deep drawing die, Matriz embutición, Ziehform, Mécanique rupture, Fracture mechanics, Mecánica ruptura, Bruchmechanik, Propriété mécanique, Mechanical properties, Propiedad mecánica, Revêtement, Coatings, Revestimiento, Ueberzug, Rupture, coatings, contact interaction, fracture, and stress analysis

The periodic contact problem for the system of dies and two-layered elastic foundation is considered. The imperfect adhesion between the layer and the substrate is taken into account by the boundary conditions at the interface. The solution of the problem is based on Hankel transform and the methods of localisation and superposition. The results are used to evaluate internal stresses in coated bodies which are in contact with rough surface and to analyse the influence of mechanical and geometrical characteristics of the coatings and the roughness parameters on the maximum stress value and its location, and on the types of coating fractures.

Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Rupture, Fractures, Acier double phase, Dual phase steel, Acero doble fase, Dualphasenstahl, Courbe limite emboutissage, Forming limit curve, Curva límite embutición, Grenzformaenderungskurve, Courbe limite formage, Forming limit diagram, Curva límite conformado, Déformation plastique, Plastic deformation, Deformación plástica, Plastische Verformung, Ecoulement plastique, Plastic flow, Flujo plástico, Plastisches Fliessen, Etude expérimentale, Experimental study, Estudio experimental, Experimentelle Untersuchung, Etude théorique, Theoretical study, Estudio teórico, Theoretische Untersuchung, Modélisation, Modeling, Modelización, Porosité, Porosity, Porosidad, Porositaet, Rupture, Ruptura, Bruch, Propriété mécanique, Prédiction, damage, forming limits, fracture, imperfection, plastic flow localization, porosity, and probabilistic method, void shape

Ductile materials subjected to plastic deformation experience the different stages of void nucleation, growth and coalescence that eventually lead to ductile fracture. Several models have been proposed to assess the influence of this damage on flow localization and fracture. In general, the plastic behaviour is represented by a constitutive model for porous or damaged materials. It is typical to introduce a material imperfection, with porosity higher than average, which evolves up to localization and fracture. However, the void volume fraction in the imperfection is chosen more or less arbitrarily. In the present ivfirk, a model that evaluates this void volume fraction more rigorously is developed. The forming limit diagram (FLD) for a dual phase-steel is calculated using the damage-based imperfection calculation and validated with experimental results. The effect of void shape on the imperfection porosity level and limit strains in sheet forming is also assessed with the present method.

Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Transformation de matériaux métalliques, Production techniques, Métallurgie des poudres. Matériaux composites, Powder metallurgy. Composite materials, Délaminage, Delamination, Delaminación, Schichtabloesung, Energie déformation, Strain energy, Energía deformación, Matériau composite, Composite material, Material compuesto, Verbundwerkstoff, Modélisation, Modeling, Modelización, Méthode élément fini, Finite element method, Método elemento finito, Finite Element Methode, Plaque stratifiée, Laminated plate, Placa estratificada, Propagation fissure, Crack propagation, Propagación fisura, Rissausbreitung, Propriété mécanique, Mechanical properties, Propiedad mecánica, composites, delamination, mixed mode delamination, and strain energy release rate

Delamination is one of the most frequent failure modes in laminated composites. Its importance is crucial, because a delamination can occur in the interior of a panel without any noticeable damage on the surface, drastically reducing its strength and stiffness. A study has to be made on critical dimensions of delaminations and their shape, through the calculation of the strain energy release rate (SERR), G. This study was performed numerically, for a given geometry, with varying loads and shapes of delamination, in pure and mixed-mode propagation. All numerical values were obtained with three-dimensional finite element (FE) analyses from a commercial package. The use of three-dimensional analyses in simple geometries helps establish the basis for the more complex ones, and the correspondence with the usual analytical or numerical bi-dimensional plane-strain analysis. The conclusions were (a) G is not constant along the crack tip, even for mode I propagation and straight crack tip; (b) the mean value of G obtained from a three-dimensional analysis equals the value obtained in bi-dimensional plane-strain analysis; (c) in mixed-mode propagation, the method exhibits a good correlation with experimental results and (d) the shape and mode partitioning of the SFIRR depend not only on the loading, but also on the shape of the crack front.

Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Propriétés mécaniques et acoustiques de l'état condensé, Mechanical and acoustical properties of condensed matter, Propriétés mécaniques des solides, Mechanical properties of solids, Fatigue, fragilisation, rupture et fissures, Fatigue, brittleness, fracture, and cracks, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Amorçage fissure, Crack formation, Déformation plastique, Plastic deformation, Détection IR, Infrared detection, Detección IR, Détection fissure, Crack detection, Etude expérimentale, Experimental study, Feuille métallique, Metal foil, Hoja metálica, Blattmetall, Formage, Forming processes, Mécanique rupture, Fracture mechanics, Propriété mécanique, Mechanical properties, Thermoélasticité, Thermoelasticity, Détection défaut, Germination, Rayonnement IR, Tôle, crack nucleation, infrared radiation, metalforming, plastic strains localisation, and thermoelasticity

In the present work a method is described for the early detection of large plastic strains localisation and subsequent crack nucleation in sheet metalforming. The method is based on the monitoring of the infrared radiation emitted from the material during stretching. It is concluded that the point of the final crack nucleation can be located in the verv early stages of stretching, when overall mean strains are insignificant (less than 20% of the yielding strain of the material).

Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Propriétés mécaniques et acoustiques de l'état condensé, Mechanical and acoustical properties of condensed matter, Propriétés mécaniques des solides, Mechanical properties of solids, Fatigue, fragilisation, rupture et fissures, Fatigue, brittleness, fracture, and cracks, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Déformation plastique, Plastic deformation, Equation cinétique, Kinetic equations, Etude théorique, Theoretical study, Modèle mécanique, Mechanical model, Modelo mecánico, Mécanique rupture, Fracture mechanics, Métal, Metals, Propriété mécanique, Mechanical properties, Cinétique, damage mechanics, and plastic loosening

Plastic deformation of metals leads to the residual variation of the volume of the metal due to the appearance and growth of deformational defects. This process is known as defect accumulation'. The intensity of this process depends on the metal properties and loading parameters. This work is concentrated first of all with experiments, used to set up the physically substantiated model of damage accumulation under complex stress states. A special technique allowed the loading of the specimens under various superimposed hydrostatic pressures (0.1-800 MPa) to simulate the process of damage accumulation under a wide range of stress states. The metal density was chosen as the characteristic of damage. The experiments support hypotheses of a linear dependence between the damage accumulation intensity and the controlling stress state index, and an inverse exponential dependence of the critical damage accumulation.

Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Assemblage et découpage thermique: aspects métallurgiques, Joining, thermal cutting: metallurgical aspects, Soudage, Welding, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Fatigue, Propriété mécanique, Mechanical properties, Propiedad mecánica, Soudage, Welding, Soldadura, Schweissen, Aluminium, Aluminio, Assemblage soudé, Welded joint, Ensamblaje soldado, Schweissverbindung, Charge multiaxiale, Multiaxial load, Carga multiaxial, Durée vie fatigue, Fatigue life, Longevidad fatiga, Ermuedungslebensdauer, Fatigue, Fatiga, Ermuedung, aluminium welds, bending and torsion, critical plane, and multiaxial stress state

Multiaxial stress states occur in many welded constructions like chemical plants, railway carriages and frames of trucks. Those stresses can have constant and changing principal stress directions, depending on the loading mode. Latest research results on welded steel joints show a loss of fatigue life for changing principal stress directions simulated by outer-phase bending and torsion compared to constant directions given by in-phase loading. However, aluminium welds reveal no influence of changing principal directions on fatigue life compared to multiaxial loading with constant principal stress directions. This behaviour is not predictable by any conventional hypothesis. A hypothesis on the basis of local normal and shear stresses in the critical plane has been developed and applied to aluminium weldings.

Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Assemblage et découpage thermique: aspects métallurgiques, Joining, thermal cutting: metallurgical aspects, Soudage, Welding, Soudage, Welding, Soldadura, Schweissen, Assemblage soudé, Welded joint, Ensamblaje soldado, Schweissverbindung, Charge biaxiale, Biaxial load, Carga biaxial, Fatigue, Fatiga, Ermuedung, Propriété mécanique, Mechanical properties, Propiedad mecánica, damage summation, load-life curves, mountain bike, safety standards, variable amplitude fatigue, and welded components

This paper presents the experimental evaluation of the fatigue behaviour of welded components under non-proportional variable amplitude biaxial loads. The study was undertaken on welded mountain bike handlebar stems, which were different in terms of geometry and technology and tested with load histories that were reconstructed and accelerated from recorded field data. Loads measured in the field were decomposed into bending and torsional components; a synchronous Peak-Valley counting, a spectrum inflation technique, a spline interpolation and a final amplification were applied to the measured signals in order to obtain test drive signals with the correct content of biaxial non-proportional loadings. After evaluation of the bending and torsion load-life curves of components under constant amplitude fatigue, the resulting data from biaxial variable amplitude fatigue tests were analysed in order to evaluate the damage contribution as a result of the two load components and an equivalent simplified two-stage constant amplitude fatigue test was proposed to the working group ISO/SC1/TC149/WG4.

Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Fatigue, Propriété mécanique, Mechanical properties, Propiedad mecánica, Charge multiaxiale, Multiaxial load, Carga multiaxial, Critère fatigue, Fatigue criterion, Criterio fatiga, Défaut matériau, Material defect, Defecto material, Werkstoffehler, Fatigue, Fatiga, Ermuedung, Résistance fatigue, Fatigue strength, Resistencia fatiga, Dauerfestigkeit, defects, multiaxial fatigue, scale effects, small cracks, and springs

Estimation of fatigue strength under biaxial and multiaxial loading is usually based on the assumption that fatigue limit is the limit stress for crack nucleation. However, in presence of defects and inhomogeneities the fatigue limit is determined by the threshold condition of small cracks. Nevertheless, multiaxial criteria, especially the Dang Van's criterion, could be successfully applied to defective materials. The scope of this paper is to discuss the differences in the two approaches (multiaxial criteria versus mechanics of the small cracks) for fatigue design of components containing defects subjected to biaxial and multiaxial in-phase loading. In particular it will be discussed, on the basis of the fatigue properties of large springs, the need of a correct description of the fatigue mechanism in order to determine the lower bound of fatigue strength in presence of defects.

Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Propriétés mécaniques et acoustiques de l'état condensé, Mechanical and acoustical properties of condensed matter, Propriétés mécaniques des solides, Mechanical properties of solids, Fatigue, fragilisation, rupture et fissures, Fatigue, brittleness, fracture, and cracks, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Déformabilité, Deformability, Deformabilidad, Essai mécanique, Mechanical tests, Etude théorique, Theoretical study, Forgeabilité, Workability, Formabilité, Formability, Formabilidad, Formbarkeit, Mécanique rupture, Fracture mechanics, Propriété mécanique, Mechanical properties, Rupture, Ruptures, Surface libre, Free surface, Superficie libre, Essai refoulement, Refoulement, formability, free surface fracture, and metal forming

To determine a workability diagram for bulk metal forming processes, it is proposed to use experiments in which fracture occurs at a free surface. A good example of such experiments is an upsetting test with profiled dies. An advantage of this method is that fracture conditions are formulated in terms of strain components whereas stresses are excluded using an exact theoretical solution. In the present study three axisymmetric upsetting tests, with flat dies and with conical dies, are carried out to determine the strain to fracture. The method proposed is then combined with these experimental data to find an approximation to the workability diagram of a tool steel.

Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Fatigue, Propriété mécanique, Mechanical properties, Propiedad mecánica, Critère fatigue, Fatigue criterion, Criterio fatiga, Fatigue oligocyclique, Low cycle fatigue, Fatiga oligocíclica, Ermuedung bei niedrigen Lastspielzahlen, Fatigue, Fatiga, Ermuedung, Limite fatigue, Fatigue limit, Límite fatiga, Ermuedungsgrenze, Méthode étude, Investigation method, Método estudio, Untersuchungsmethode, dissipated energy, high cycle fatigue, low cycle fatigue, and shakedown

The purpose of this paper is to present a unified analysis to both high and low cycle fatigue based on shakedown theories and dissipated energy. The discussion starts with a presentation of the fatigue phenomena at different scales (microscopic, mesoscopic and macroscopic) and of the main shakedown theorems. A review of the Dang Van high cycle fatigue criterion shows that this criterion is essentially based on the hypothesis of elastic shakedown and can therefore be expressed as a bounded cumulated dissipated energy. In the low cycle fatigue regime, recent results by Skelton and Charkaluk et al. show that we can speak of a plastic shakedown at both mesoscopic and macroscopic scale and of a cumulated energy bounded by the failure energy. The ideas are also justified by infrared thermography tests permitting a direct determination of the fatigue limit.

Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Fatigue, Propriété mécanique, Mechanical properties, Propiedad mecánica, Charge aléatoire, Random load, Carga aleatoria, Zufaellige Belastung, Charge multiaxiale, Multiaxial load, Carga multiaxial, Critère fatigue, Fatigue criterion, Criterio fatiga, Dommage cumulatif, Cumulative damage, Daño cumulativo, Schadensakkumulation, Fatigue, Fatiga, Ermuedung, Modélisation, Modeling, Modelización, critical plane approach, multiaxial high-cycle fatigue, random loading, and weight function method

A multiaxial fatigue criterion for random loading is proposed. Firstly, the orientation of the critical plane, where fatigue life estimation is carried out, is determined from the weighted mean position of the principal stress directions. Then, the scalar value of the normal stress vector N(t) perpendicular to the critical plane is taken as the cycle counting variable since the direction of such a vector is fixed with respect to time (conversely to the time-varying direction of the shear stress vector C(t)), and a nonlinear combination of normal and shear stress components acting on the critical plane is used to define an equivalent stress amplitude. Finally, a damage accumulation model is employed to process such an equivalent stress amplitude and to determine fatigue endurance. This criterion is herein applied to some relevant random fatigue tests (proportional bending and torsion).

Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Elasticité. Plasticité, Elasticity. Plasticity, Eprouvette préfissurée, Precracked specimen, Probeta preagrietada, Angerissene Probe, Facteur intensité contrainte, Stress intensity factor, Factor intensidad tensión, Spannungsintensitaetsfaktor, Modélisation, Modeling, Modelización, Méthode élément fini, Finite element method, Método elemento finito, Finite Element Methode, Propagation fissure, Crack propagation, Propagación fisura, Rissausbreitung, Propriété mécanique, Mechanical properties, Propiedad mecánica, corner point singularities, cracks, finite element analysis, and stress intensity factors

Finite element analyses were carried out on cracked 20mm square plates and bars ranging in thickness from 2.5 mm to a length of 60 mm. The crack extended from the middle of one side of the square to its centre, and was modelled as a narrow, parallel-sided notch with a semicircular tip. An antiplane loading was applied to the side containing the crack. An infinitely long bar under the antiplane loading used is in pure Mode III. It was found that the central portions of 40, 56 mm and 60 mm long bars were in pure Mode III, and also that KIII was approximately constant. These central portions were therefore representative of an infinitely long bar. Towards the ends of a bar KIII decreased. At the ends of a bar corner point effects meant that Mode II stress intensity factors and displacements were induced in the corner region. The size of the corner region was independent of bar length. In the 2.5, 5 and 10 mm thick plates out of plane bending means that the antiplane loading became a mixed Mode II and Mode III loading. At a centre line KII is zero by symmetry. Behaviour in the corner region was a function of plate thickness. For both plates and bars, as has been predicted theoretically, the ratio KII/KIII tends to a constant value as a surface is Approached. For a thickness of 20mm, that is a 20-mm cube, behaviour represents a transition between plate and bar behaviour.

Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Propriétés mécaniques et acoustiques de l'état condensé, Mechanical and acoustical properties of condensed matter, Propriétés mécaniques des solides, Mechanical properties of solids, Fatigue, fragilisation, rupture et fissures, Fatigue, brittleness, fracture, and cracks, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Acier chrome, Chromium steels, Acier roulement, Ball bearing steel, Acero rodamiento de bolas, Kugellagerstahl, Acier, Steels, Contrainte compression, Compressive stress, Tensión compresión, Druckspannung, Contrainte résiduelle, Residual stresses, Essai fatigue, Fatigue testing, Etude expérimentale, Experimental study, Fatigue plastique, Plastic fatigue, Fatiga plástica, Fatigue polycyclique, High cycle fatigue, Fatiga polyciclica, Grenaillage, Shot peening, Microscopie électronique balayage, Scanning electron microscopy, Propriété mécanique, Mechanical properties, Traitement surface, Surface treatments, and Acier Cr1

Effect of shot-peening on fatigue behaviour in the gigacycle regime was investigated in order to clarify the duplex S-N curve characteristics. Cantilever-type rotary bending fatigue tests were performed in laboratory air at room temperature by using hourglassshaped specimens of high-carbon-chromium bearing steel, JIS SUJ2. Fatigue crack initiation site changed from the surface of untreated specimen to the subsurface of the specimen because of hardening and compressive residual stress with shot-peening in the region of high-stress amplitude. On the other hand, no difference in fatigue life controlled by the subsurface crack initiation between untreated specimen and shot-peening one was observed in high-cycle region. It was suggested that the S-N curve corresponding to the internal fracture mode is inherent in the material, as compared with the S-N curve of surface fracture mode, which is affected by surface conditions, environmental conditions and so on. Subsurface crack initiation and propagation behaviour were discussed under the detailed measurement of crack initiation area and shape of the fish-eye fracture surface.

Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Propriétés mécaniques et acoustiques de l'état condensé, Mechanical and acoustical properties of condensed matter, Propriétés mécaniques des solides, Mechanical properties of solids, Fatigue, fragilisation, rupture et fissures, Fatigue, brittleness, fracture, and cracks, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Acier, Steels, Durée vie fatigue, Fatigue life, Longevidad fatiga, Ermuedungslebensdauer, Essai flexion alternée, Bending fatigue test, Prueba flexión alternada, Hin und Herbiegeversuch, Etude expérimentale, Experimental study, Fatigue plastique, Plastic fatigue, Fatiga plástica, Fatigue polycyclique, High cycle fatigue, Fatiga polyciclica, Flexion, Bending, Fractographie, Fractography, Microscopie électronique balayage, Scanning electron microscopy, Tube métallique, Metal tube, Tubo metálico, Tube paroi mince, Thin wall tube, Tubo pared delgada, Tube, and Tubes

Fatigue life data of cold worked tubes (diameter 4mm, wall thicknesses 0.25 and 0.30 mm) of an austenitic stainless steel, AISI 904 L, were measured in the regime ranging from 2 x 105 to 1010 cycles to failure. The influence of the loading frequency was investigated as data were obtained in conventional rotating bending at 160 and 200Hz and in ultrasonic axial loading at 20kHz. Above 5 x 106 cycles the fatigue lifetimes found with both methods were comparable. The results show that the slope of the S-N curve significantly decreases beyond 108 cycles. Fracture surfaces were examined using scanning electron microscopy. Fatigue cracks initiate at the surface and no significant influence from frequency or from loading modes on fatigue crack initiation and growth is visible.

Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Propriétés mécaniques et acoustiques de l'état condensé, Mechanical and acoustical properties of condensed matter, Propriétés mécaniques des solides, Mechanical properties of solids, Fatigue, fragilisation, rupture et fissures, Fatigue, brittleness, fracture, and cracks, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Amplitude vibration, Vibration amplitude, Amplitud vibración, Contrainte seuil, Threshold stress, Tension umbral, Durée vie fatigue, Fatigue life, Longevidad fatiga, Ermuedungslebensdauer, Essai fatigue, Fatigue testing, Etude expérimentale, Experimental study, Facteur intensité contrainte, Stress intensity factors, Fatigue plastique, Plastic fatigue, Fatiga plástica, Fatigue polycyclique, High cycle fatigue, Fatiga polyciclica, Fractographie, Fractography, Limite fatigue, Fatigue limit, Límite fatiga, Ermuedungsgrenze, Méthode essai, Test method, Método ensayo, Propriété mécanique, and Mechanical properties

Ultrasonic fatigue testing is appropriate to perform random loading tests in the regime of very high numbers of cycles. It has been shown that neither an endurance limit nor a threshold stress intensity exists under loading with randomly varying amplitudes even for materials that do show these limits under constant amplitude loading conditions. The technical features of the ultrasonic testing technique in order to perform random fatigue tests are shortly described. Endurance tests were performed on smooth specimens of AlSi7Mg (A356.0) aluminium alloy and on notched AISI 4142 and C45 steel specimens. The previous studies of crack propagation and threshold behaviour on AISI 420 ferritic chromium steel and GGG 100-B cast iron are included. Experimental results on lifetime and fatigue crack growth measurements under randomly varying amplitudes, as well as lifetime predictions, based on constant amplitude measurements and damage accumulation calculations are reported.