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Mechanical engineering, Génie mécanique, 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, Charge variable, Variable load, Carga variable, Ungleichmaessige Beanspruchung, Contrainte seuil, Threshold stress, Tension umbral, Fatigue, Fatiga, Ermuedung, Fissure courte, Short crack, Fisura corta, Propriété mécanique, Mechanical properties, Propiedad mecánica, Non-propagating small cracks, Threshold stress intensities, Ultrasonic fatigue, Variable amplitude loading, and Very high cycle fatigue (VHCF)

Ever since high-strength steels were found to fail below the traditional fatigue limit when loaded with more than 108 cycles, the investigation of metals' and alloys' very high cycle fatigue properties has received increased attention. A lot of research was invested in developing methods and machinery to reduce testing times. This overview outlines the principles and testing procedures of very high cycle fatigue tests and reports findings in the areas of crack formation, non-propagating small cracks, long crack propagation and thresholds. Furthermore, superimposed and variable amplitude loading as well as frequency effects are reported.

Mechanical engineering, Génie mécanique, 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, Alliage base aluminium, Aluminium base alloys, Charge variable, Variable load, Carga variable, Ungleichmaessige Beanspruchung, Fatigue, Fatiga, Ermuedung, Propriété mécanique, Mechanical properties, Propiedad mecánica, 2024 Aluminium alloy, Damage accumulation, Ultrasonic fatigue, Variable amplitude loading, and Very high cycle fatigue

Ultrasonic fatigue tests with variable amplitude are performed for the first time at positive load ratios. The method utilising ultrasonic equipment, a servo-hydraulic or electromechanical load frame and computer control is described. Aluminium alloy 2024-T351 is tested at approximately 20 kHz with variable amplitude in the high cycle fatigue (HCF) and very high cycle fatigue (VHCF) regime at load ratios R = -1, R = 0.1 and R = 0.5. Constant amplitude data are available and are used for Miner damage accumulation calculations. For load ratio R = -1, the mean damage sum decreases from 0.5 to 0.3 when lifetimes increase from the HCF regime to 109 cycles, and increases at higher numbers of cycles. For load ratio R = 0.1, the mean damage sum decreases from 1.1 to 0.2 when lifetimes increase from HCF to VHCF. At load ratio R = 0.5, the mean damage sum is approximately 0.1 in the VHCF regime. Cracks leading to VHCF failures start at broken constituent particles, probably Al7Cu2(Fe,Mn), or at agglomerations of fractured particles. Crack initiation occurs at the surface or less frequently in the interior.

Mechanical engineering, Génie mécanique, 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 cémenté, Case hardened steel, Acero cementado, Amorçage fissure, Crack initiation, Iniciación grieta, Risseinleitung, Fatigue, Fatiga, Ermuedung, Microstructure, Microestructura, Mikrogefuege, Propriété mécanique, Mechanical properties, Propiedad mecánica, Case-hardened steel, Competing sites of crack initiation, Kitagawa diagram, and Very high cycle fatigue (VHCF)

In this investigation notched and fracture mechanics specimens were machined from the steel SAE 5120 (DIN EN 20MnCr5) in two cleanliness conditions. The first material is used for high-performance components and is nearly free of oxides. The second material is standard steel and used for common requests in the field of drive engineering containing non-metallic inclusions in a dimension that is state of the art in steel making. The notched specimens were case-hardened in two different ways. Afterwards, the surfaces were ground and therefore showed compressive residual stresses. Uniaxial VHCF tests were performed up to 200 million cycles under the stress ratios R = ―1 and R = 0 using two resonant pulse systems. For this purpose the geometries of the specimens had been optimised so that the achieved test frequency was 190 Hz. Fatigue failure is possible at all applied numbers of cycles meaning that there is no real fatigue limit in this region. Fatigue crack initiation took place from different origins and at different sites. Different analyses are shown for interpretating the type of fatigue crack initiation and its site in the specimen. The fracture mechanics specimens were blank hardened in order to have the core properties of the notched specimens. Crack propagation was measured in the near-threshold region. An extended Kitagawa diagram is shown to demonstrate the influence of stress amplitude and flaw size on the failure probability.

Chemical industry parachemical industry, Industrie chimique et parachimique, Mechanics acoustics, Mécanique et acoustique, 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, Industrie des polymeres, peintures, bois, Polymer industry, paints, wood, Technologie des polymères, Technology of polymers, Formes d'application et semiproduits, Forms of application and semi-finished materials, Stratifiés, Laminates, Analyse contrainte, Stress analysis, Análisis tensión, Etude théorique, Theoretical study, Estudio teórico, Matériau aiguilleté, Needled material, Material cosado, Matériau composite, Composite material, Material compuesto, Matériau fibre unidirectionnelle, Unidirectional fiber material, Material fibra unidireccional, Modélisation, Modeling, Modelización, Méthode élément fini, Finite element method, Método elemento finito, Propriété mécanique, Mechanical properties, Propiedad mecánica, Propriété travers court, Through thickness property, Propiedad corta travesía, Résistance compression, Compressive strength, Resistencia compresión, Résistance traction, Tensile strength, Resistencia tracción, Simulation numérique, Numerical simulation, Simulación numérica, Stratifié, Laminate, Estratificado, Tissu textile, Woven material, Tela textil, A. Fabrics/textiles, A. Polymer-matrix composites (PMCs), C. Analysis, and D. Mechanical testing

A multiscale approach is used to predict transverse tensile and transverse compressive strength of unidirectional non-crimp fabric (NCF) composites. Numerical analysis on fibre/matrix scale is performed to obtain the transverse strength of the fibre bundle to be further used in an analytical mesoscale model to predict the strength of the unidirectional NCF composite. Design of unidirectional layer composites with the same fibres, interface, matrix and volume fractions as in the bundle is suggested as an alternative method for bundle strength determination. Good agreement of both methods for bundle transverse strength determination is demonstrated. The simple analytical model used on mesoscale gives accurate predictions of the tensile transverse strength whereas the compressive strength is underestimated. The necessity of including bundle waviness in models when bidirectional NCF composites are analysed is demonstrated by FEM stress analysis and by experimental data showing differences in transverse cracking pattern due to bundle waviness.

Mechanical engineering, Génie mécanique, 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 austénito ferritique, Austenitic ferritic steel, Acero ferrítico austenítico, Austenitisch ferritischer Stahl, Acier double phase, Dual phase steel, Acero doble fase, Dualphasenstahl, Acier inoxydable duplex, Duplex stainless steel, Acero inoxidable duplex, Acier inoxydable, Stainless steel, Acero inoxidable, Nichtrostender Stahl, Contrainte thermomécanique, Thermomechanical stress, Tensión termomecánica, Décomposition spinodale, Spinodal decomposition, Decomposición espinodal, Spinodale Entmischung, Fatigue, Fatiga, Ermuedung, Point Curie, Curie temperature, Punto Curie, Curie Temperatur, Propriété mécanique, Mechanical properties, Propiedad mecánica, Température, Temperature, Temperatura, Temperatur, and Thermo mechanical fatigue

The thermo mechanical fatigue behaviour of a ferritic-austenitic duplex stainless steel has been investigated in a temperature range of 350-600 °C. The Curie temperature (TCURIE) was determined by an abrupt increase of the power of the inductive heating device and a small control deviation of the temperature. Thus, according to Tavares et al. [1] the evolution of the spinodal decomposition in the DSS was characterised by the shift of the Curie temperature for each test. The results are compared with ageing and annealing experiments in combination with tensile tests at room temperature. In addition, microstructure observations were performed in a field-emission scanning electron microscope.

Mechanical engineering, Génie mécanique, 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, Corrosion, Action des agents de corrosion, Corrosion environments, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Fatigue, Techniques de l'ingénieur appliqués à la métallurgie. Applications. Divers, Engineering techniques in metallurgy. Applications. Other aspects, Applications, Industrie automobile, Automotive engineering, Application, Aplicación, Anwendung, Châssis véhicule, Vehicle chassis, Chasis vehículo, Fahrgestell, Conception, Design, Diseño, Gestaltung, Corrosion sel, Salt corrosion, Corrosión sal, Salzkorrosion, Durée vie, Lifetime, Tiempo vida, Lebensdauer, Fatigue, Fatiga, Ermuedung, Industrie automobile, Automobile industry, Industria automóvil, Autoindustrie, Propriété mécanique, Mechanical properties, Propiedad mecánica, Forged aluminium, Special events, Spectrum loading, and Tension strut

The structural durability design of a tension strut of forged aluminium (EN AW 6082 T6), which is a safety component of the automotive chassis, is described. The first step of the structural durability design is the knowledge of the mechanical and environmental loadings. The mechanical loadings are the spectrum loading for the designated normal driving conditions and unintended special event loadings by e.g. braking over road bumps, which are introduced into the component through the wheels. The local stresses imposed on the component are also influenced by kinematics, stiffness, axle mass, dampers, bearings, bump geometry, etc. The environmental loading is the corrosion caused, in winter-time, by salty water on the roads. For design according to the local stress concept, the knowledge of Woehler-curves without and with salt corrosion effects is necessary. On this basis, cumulative fatigue under spectrum loading, which also comprises the special events mentioned, is assessed for a standard configuration and for an optimised one. The numerical results are verified by experimental proofs on the component in the laboratory and on the proving ground as well as by field tests with vehicles.

Chemical industry parachemical industry, Industrie chimique et parachimique, Mechanics acoustics, Mécanique et acoustique, 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, Industrie des polymeres, peintures, bois, Polymer industry, paints, wood, Technologie des polymères, Technology of polymers, Formes d'application et semiproduits, Forms of application and semi-finished materials, Stratifiés, Laminates, Epoxyde résine, Epoxy resin, Epóxido resina, Etude théorique, Theoretical study, Estudio teórico, Fibre minérale, Mineral fiber, Fibra inorgánica, Fibre verre, Glass fiber, Fibra vidrio, Matériau composite, Composite material, Material compuesto, Matériau renforcé fibre, Fiber reinforced material, Material reforzado fibra, Mode rupture, Fracture mode, Modo ruptura, Modèle 3 dimensions, Three dimensional model, Modelo 3 dimensiones, Modèle statistique, Statistical model, Modelo estadístico, Modélisation, Modeling, Modelización, Mécanique rupture, Fracture mechanics, Mecánica ruptura, Méthode élément fini, Finite element method, Método elemento finito, Propagation fissure, Crack propagation, Propagación fisura, Propagation oblique, Oblique propagation, Propagación oblicua, Propriété mécanique, Mechanical properties, Propiedad mecánica, Propriété traction, Tensile property, Propiedad tracción, Simulation numérique, Numerical simulation, Simulación numérica, Stratifié, Laminate, Estratificado, Vérification expérimentale, Experimental test, Verificación experimental, Matériau fibre multidirectionnelle, Stratifié croisé, A. Polymer-matrix composites, B. Defects, C. Damage mechanics, and C. Statistical properties/methods

A previously developed statistical model for transverse cracking in cross ply laminates is extended to oblique cracking in multidirectional laminates. The oblique cracks are assumed to form in a ply when the local in-plane tensile stress normal to fibers exceeds the transverse strength of the ply. This strength is assumed to have a statistical distribution given by a two-parameter Weibull function. The model is applied to a glass-epoxy [0/602/0/-602]5 laminate in which cracking evolution of the four -60° plies in the middle of the laminate is examined. The local stress field in the cracked -60° plies is calculated by a three-dimensional finite element method based on a unit cell construction developed by Li et al. [1]. The measured crack density is found to agree well with that calculated by the statistical model.

Mechanical engineering, Génie mécanique, 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, Anisotropie, Anisotropy, Anisotropía, Fatigue, Fatiga, Ermuedung, Glissement, Slip, Deslizamiento, Gleiten, Joint grain, Grain boundary, Limite grano, Korngrenze, Microstructure, Microestructura, Mikrogefuege, 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, Prédiction, Prediction, Predicción, Système glissement, Slip system, Sistema deslizamiento, Gleitsystem, Crack path, and Extended finite element

This study develops a new method for the analysis of fatigue crack growth at micro-structural scale. Proposed model was constructed based on material anisotropic properties and crystallographic planes. In this research, it has been attempted to suggest an accurate and precise criterion for the prediction of crack growth path at micro-structural scales by the study of various criteria for crack growth. For this purpose, considering fracture energy for trans-granular and inter-granular fracture as well as dominant slip planes, a criterion was proposed to predict crack growth. In the current research, fatigue tests were performed on two different alloys and the real path of the crack growth was obtained. Next, by the simulation of tested pieces through finite element software (ABAQUS) and using extended finite element method, various criteria to predict crack growth path were studied. The microstructures of both specimens tested in considered areas were modelled with an anisotropic behaviour and their crystal orientations were gained using electron-back-scattering-diffraction-pattern (EBSP) method. The results suggest the accuracy and precision of proposed criterion with minor error in single-phase alloys and major difference in two-phase alloys.

Mechanical engineering, Génie mécanique, 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 austénito ferritique, Austenitic ferritic steel, Acero ferrítico austenítico, Austenitisch ferritischer Stahl, Acier double phase, Dual phase steel, Acero doble fase, Dualphasenstahl, Acier inoxydable, Stainless steel, Acero inoxidable, Nichtrostender Stahl, Fatigue oligocyclique, Low cycle fatigue, Fatiga oligocíclica, Ermuedung bei niedrigen Lastspielzahlen, Fissure courte, Short crack, Fisura corta, Fissure fatigue, Fatigue crack, Fisura fatiga, Ermuedungsriss, Modélisation, Modeling, Modelización, Propagation fissure, Crack propagation, Propagación fisura, Rissausbreitung, Propriété mécanique, Mechanical properties, Propiedad mecánica, Duplex steel, LCF, Short fatigue cracks, and VHCF

The present paper reviews experimental results on the fatigue damage of austenitic-ferritic duplex steel under various load levels ranging from LCF to VHCF, placing the focus towards the relationship between the crystallographic orientation of individual grains and grain patches that exhibit slip band formation, fatigue crack initiation and growth. A combination between fatigue testing of electropolished specimens and analytical electron microscopy (SEM/EBSD, TEM) revealed that under LCF loading conditions almost all the ferrite and the austenite grains showed plasticity, while under HCF and VHCF loading conditions, slip band formation was limited to the softer austenite grains and a low plastic activity is observed in the ferrite. Once being formed, the bands generate high stress concentrations, where they impinge the α-γ phase boundaries, eventually, leading to the crack initiation. This is discussed by applying a numerical simulation approach based on the finite-element (FEM) and the boundary-element (BEM) 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, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Rupture, Fractures, Propriété mécanique, Mechanical properties, Propiedad mecánica, Température transition, Transition temperature, Temperatura transición, Uebergangstemperatur, Transition ductile fragile, Ductile brittle transition, Transición ductil frágil, Uebergang duktil sproed, T-stress, constraint, material failure master curve, subsize Charpy specimen, and transition temperature

The ductile―brittle transition temperature is not intrinsic to steel but depends on the specimen type and loading mode used for the test. The influence of these parameters is related to the plastic constraint. Here, the constraint is evaluated by the effective T-stress obtained by the stress difference method on the notch tip stress distribution. From Charpy energy values at different temperatures, it is possible to obtain a material failure master curve where the notch fracture toughness is plotted versus the shift of test temperature with the transition temperature corresponding to the effective T-stress value. Values of the critical effective T-stress are obtained for three subsize Charpy specimens (3/4, 1/2 and 1/3) and are reported on a material transition temperature master curve versus effective T-stress. This allows obtaining the shift of transition temperature when comparing with those of a standard Charpy V specimen. The results do not confirm the prediction given by the empirical relation of the ASME.

Chemical industry parachemical industry, Industrie chimique et parachimique, Mechanics acoustics, Mécanique et acoustique, 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, Industrie des polymeres, peintures, bois, Polymer industry, paints, wood, Technologie des polymères, Technology of polymers, Formes d'application et semiproduits, Forms of application and semi-finished materials, Stratifiés, Laminates, Charge multiaxiale, Multiaxial load, Carga multiaxial, Diagramme SN, SN diagram, Diagrama SN, Endommagement, Damaging, Deterioración, Epoxyde résine, Epoxy resin, Epóxido resina, Essai fatigue, Fatigue test, Ensayo fatiga, Etude expérimentale, Experimental study, Estudio experimental, Fibre minérale, Mineral fiber, Fibra inorgánica, Fibre verre, Glass fiber, Fibra vidrio, Matériau composite, Composite material, Material compuesto, Matériau renforcé fibre, Fiber reinforced material, Material reforzado fibra, Mode empilement, Stacking sequence, Modo apilamiento, Modèle mécanique, Mechanical model, Modelo mecánico, Modélisation, Modeling, Modelización, Mécanique rupture, Fracture mechanics, Mecánica ruptura, Propagation fissure, Crack propagation, Propagación fisura, Propriété mécanique, Mechanical properties, Propiedad mecánica, Résistance fatigue, Fatigue strength, Resistencia fatiga, Stratifié, Laminate, Estratificado, Tube, Tubo, Effet épaisseur, A. Laminates, B. Fatigue, C. Damage mechanics, and Multiaxial fatigue

In this work an experimental investigation on damage initiation and evolution in laminates under cyclic loading is presented. The stacking sequence [0/02/0/-02]s has been adopted in order to investigate the influence of the local multiaxial stress state in the off-axis plies and the possible effect of different thickness between the thin (2-plies) and the thick (4-plies) layers. Results are presented in terms of S-N curves for the initiation of the first cracks, crack density evolution, stiffness degradation and Paris-like curves for the crack propagation phase. The values of the off-axis angle 0 has been chosen in order to obtain local multiaxial stress states in the off-axis plies similar to those in previous studies for biaxially loaded tubes. Results concerning damage initiation and growth for these two specimen configurations are shown to be consistent for similar local multiaxial stress states.

Chemical industry parachemical industry, Industrie chimique et parachimique, Mechanics acoustics, Mécanique et acoustique, 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, Industrie des polymeres, peintures, bois, Polymer industry, paints, wood, Technologie des polymères, Technology of polymers, Formes d'application et semiproduits, Forms of application and semi-finished materials, Stratifiés, Laminates, Emission acoustique, Acoustic emission, Emisión acústica, Epoxyde résine, Epoxy resin, Epóxido resina, Etude expérimentale, Experimental study, Estudio experimental, Fibre carbone, Carbon fiber, Fibra carbón, Fibre minérale, Mineral fiber, Fibra inorgánica, Fibre verre, Glass fiber, Fibra vidrio, Matériau composite, Composite material, Material compuesto, Matériau fibre unidirectionnelle, Unidirectional fiber material, Material fibra unidireccional, Matériau renforcé fibre, Fiber reinforced material, Material reforzado fibra, Mode rupture, Fracture mode, Modo ruptura, Méthode mesure, Measurement method, Método medida, Méthode non destructive, Non destructive method, Método no destructivo, Orientation fibre, Fiber orientation, Orientación fibra, Propriété mécanique, Mechanical properties, Propiedad mecánica, Rupture fibre, Fibre fracture, Ruptura fibra, Résistance traction, Tensile strength, Resistencia tracción, Ténacité, Fracture toughness, Tenacidad, Uréthanne polymère, Polyurethane, Uretano polímero, A. Polymer-matrix composites (PMCs), B. Fatigue, D. Acoustic emission, D. Mechanical testing, and Thermosetting polyurethane

Acoustic emission analysis is used to investigate microscopic damage mechanisms and damage progress in unidirectional glass and carbon fibre reinforced composites. Under static loading the influence of fibre orientation on damage initiation and propagation is determined. A novel polyurethane matrix system significantly enhances material performance in terms of crack initiation load levels, crack growth, damage tolerance and off-axis tensile strength. Hysteresis measurements during stepwise increasing dynamic load tests highlight the effect of fibre-matrix-adhesion and resin fracture toughness in unidirectional 0° fibre reinforced composites. Acoustic detection of beginning fibre breakage correlates with a significant increase of loss work per cycle.

Mechanical engineering, Génie mécanique, 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, Métaux renforcés par des fibres, Fibre reinforced metals, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Fatigue, Amortissement, Damping, Amortiguación, Durée vie fatigue, Fatigue life, Longevidad fatiga, Ermuedungslebensdauer, Fatigue, Fatiga, Ermuedung, Fibre verre, Glass fiber, Fibra vidrio, Matériau composite, Composite material, Material compuesto, Verbundwerkstoff, Métal renforcé fibre, Fibre reinforced metal, Metal reforzado fibra, Faserverstaerktes Metall, Propriété mécanique, Mechanical properties, Propiedad mecánica, Prédiction, Prediction, Predicción, Composites, Frequency response function (FRF), and Natural frequency

The main objective of the present work is to investigate the capability of experimental modal analysis as a nondestructive tool to characterize and quantify the fatigue behavior of laminated composite beam with different lamina orientations and cantilevered boundary condition. In the present work, experimental modal analysis was conducted on the specimens previously subjected to fatigue loading to determine the modal parameters (natural frequency, damping ratio and mode shape). This was achieved through studying the response of modal testing with different specimens of different lamina orientations as a main factor affecting fatigue life. This correlates modal parameters such as: damping ratio, natural frequency and mode shape to fatigue behavior. The composite material used in experiments is glass fiber reinforced polyester (GFRP) laminate. Plane bending fatigue tests were performed on standard fatigue specimens. The fatigue test was interrupted at different fatigue life ratios (n/Nf) and modal testing was conducted to determine the change in modal parameters. The results showed that the changes of modal parameters provide a proper means for predicting the fatigue behavior of composite structures. From the experimental results of both dynamic and fatigue tests, curve fitting technique was used to correlate modal parameters to fatigue life. An exponential and quadratic equations have been obtained which correlate fatigue life ratio to damping ratio and resonant frequency respectively. It was noticed from the curves representing exponential and quadratic equations that the value of damping ratio ς is more noticeable than the value of frequency, which means that the extent of fatigue damage determines the damping ratio, hence damping ratio could be said to be a good indicator of the fatigue life ratio.

Chemical industry parachemical industry, Industrie chimique et parachimique, Mechanics acoustics, Mécanique et acoustique, 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, Industrie des polymeres, peintures, bois, Polymer industry, paints, wood, Technologie des polymères, Technology of polymers, Formes d'application et semiproduits, Forms of application and semi-finished materials, Stratifiés, Laminates, Défaut matériau, Material defect, Defecto material, Epoxyde résine, Epoxy resin, Epóxido resina, Etude expérimentale, Experimental study, Estudio experimental, Matériau composite, Composite material, Material compuesto, Matériau fibre unidirectionnelle, Unidirectional fiber material, Material fibra unidireccional, Matériau renforcé fibre, Fiber reinforced material, Material reforzado fibra, Méthode mesure, Measurement method, Método medida, Propriété mécanique, Mechanical properties, Propiedad mecánica, Préimprégné, Prepreg, Preimpregnado, Stratification, Estratificación, Stratifié, Laminate, Estratificado, Ténacité, Fracture toughness, Tenacidad, Insertion film intralaminaire, Ténacité intralaminaire, and Laminates

A novel initial crack insertion method, intralaminar film insertion method, was proposed to investigate the fracture toughness of unidirectional carbon fiber reinforced plastic (CFRP) laminates when the crack propagates inside the ply and not in the interlayer resin-rich area. Here, a release film was inserted inside a single lamina during the resin impregnation process of prepreg manufacturing. Mode I intralaminar fracture toughness tests were carried out for conventional CFRP laminates and interlayer toughened CFRP laminates. For comparison, two conventional methods were used to introduce initial cracks. One is the interlaminar film method, where a release film is inserted between two prepreg plies during the lay-up process. The other is the machined slit method, where a slit notch is machined in parallel to the layer of CFRP laminates. It was demonstrated that the proposed intralaminar film method can correctly evaluate the intralaminar fracture toughness of both conventional CFRP laminate and interlayer toughened CFRP laminate from the initial value to the propagation value. For this range, it was also found that the intralaminar fracture toughness of interlayer toughened CFRP laminate was the same as that of conventional CFRP laminate. Thus, the intralaminar fracture toughness was not influenced by interlayer toughening.

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, Charge multiaxiale, Multiaxial load, Carga multiaxial, Durée vie fatigue, Fatigue life, Longevidad fatiga, Ermuedungslebensdauer, Fatigue, Fatiga, Ermuedung, Propriété mécanique, Mechanical properties, Propiedad mecánica, Vérification expérimentale, Experimental test, Verificación experimental, experimental tests, fatigue life, fatigue, multiaxial loadings, and non-proportional loading

The shear stress amplitude is one of the most important parameters in the formulation of many multiaxial fatigue models proposed in literature. The shear stress amplitude is usually evaluated by the longest projection or the minimum circumscribed circle approach in a shear stress space. Further, the von Mises and Tresca stress spaces are the most used ones under multiaxial loading conditions, where the damage ratio between axial and shear damages is a constant value: 0.577 for von Mises and 0.5 for Tresca. However, the damage scale in each stress space's axes may vary significantly depending on materials' type. Therefore, evaluating proportional and non-proportional damages using conventional stress spaces (von Mises or Tresca) may lead to erroneous interpretations. In this work, systematic fatigue experiments under proportional and non-proportional loading conditions are presented for three structural steels: Ck45, AISI303 and the 42CrMo4. To quantify the relative damage between proportional and non-proportional loading paths, a material's non-proportional sensitivity parameter (Y parameter), determined based on materials experimental tests, is proposed. From this research, it can be drawn that the appropriate axial/shear damage relation should be used to estimate multiaxial fatigue life.

Mechanical engineering, Génie mécanique, 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, Durée vie fatigue, Fatigue life, Longevidad fatiga, Ermuedungslebensdauer, Fatigue, Fatiga, Ermuedung, Méthode contrôle, Control method, Método control, Propriété mécanique, Mechanical properties, Propiedad mecánica, Fatigue life evaluation, Maximum amplitude principle, Rainflow method, and Shadow method

It is shown in present study that Rainflow method is unable to accurately estimate fatigue life of components under random loading, almost always. The inconsistencies between results of Rainflow method and hysteresis curve are also discussed. Alike the Peak counting method, it is shown that Shadow method doesn't consider the possibility of deformation within individual cycles. Hence, Moshrefifar and Azamfar method is proposed as a novel technique having accurate results in different analytical conditions which are in good consistence with results obtained from hysteresis curves. Authors finally propose an algorithm as well as a C language program for this method.

Chemical industry parachemical industry, Industrie chimique et parachimique, Mechanics acoustics, Mécanique et acoustique, 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, Electrotechnique. Electroenergetique, Electrical engineering. Electrical power engineering, Electroénergétique, Electrical power engineering, Conversion directe et accumulation d'énergie, Direct energy conversion and energy accumulation, Conversion électrochimique: piles et accumulateurs électrochimiques, piles à combustibles, Electrochemical conversion: primary and secondary batteries, fuel cells, Batterie lithium, Lithium battery, Diffusion ion, Ion scattering, Difusión ión, Distribution concentration, Concentration distribution, Distribución concentración, Elasticité linéaire, Linear elasticity, Elasticidad lineal, Endommagement, Damaging, Deterioración, Etude théorique, Theoretical study, Estudio teórico, Exfoliation, Exfoliación, Fibre carbone, Carbon fiber, Fibra carbón, Fibre minérale, Mineral fiber, Fibra inorgánica, Ion lithium, Lithium ion, Litio ión, Matériau électrode, Electrode material, Material electrodo, Modélisation, Modeling, Modelización, Mécanique rupture, Fracture mechanics, Mecánica ruptura, Méthode élément fini, Finite element method, Método elemento finito, Propriété mécanique, Mechanical properties, Propiedad mecánica, Simulation numérique, Numerical simulation, Simulación numérica, A. Carbon fiber, and C. Finite element analysis (FEA)

Gradients in lithium ion concentration distribution in carbon fiber are accompanied by non-uniform fiber swelling leading to development of mechanical stresses. During lithium deintercalation these stresses may lead to initiation and growth of radial cracks in the fiber. The subsequent cycle of intercalation may result in arc-shaped cracks deviating from the tip of the radial cracks. These phenomena decrease the mechanical properties of fibers if used in structural batteries and reduce the charging properties of the battery by decreased diffusivity of lithium ions and by exfoliating layers on the fiber surface. The crack propagation and possible damage evolution scenarios are analyzed using linear elastic fracture mechanics. The crack geometry dependent ion concentration distributions and the elastic stress distributions were found using finite element software ANSYS.

Mechanical engineering, Génie mécanique, 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, Alliage forgé, Wrought alloy, Aleación forjada, Schmiedelegierung, Amorçage fissure, Crack initiation, Iniciación grieta, Risseinleitung, Fatigue, Fatiga, Ermuedung, Microstructure, Microestructura, Mikrogefuege, Propriété mécanique, Mechanical properties, Propiedad mecánica, Résistance fatigue, Fatigue strength, Resistencia fatiga, Dauerfestigkeit, Résistance mécanique, Strength, Resistencia mecánica, Festigkeit, Aluminum alloys, Microstructures, and Very high cycle fatigue

Fatigue studies were conducted under load control with a servo-hydraulic testing machine with smooth specimens of the aluminum wrought alloys EN AW-6056-T6 (Rm = 399 MPa) and EN AW-6082-T5 (Rm = 356 MPa) up to a maximum number of N = 2 x 108 and 109 cycles, respectively. The results show for both aluminum alloys that the fatigue strength decreases with increasing number of cycles after the kneepoint of the S-N-curve and that approximately at this point a transition of the crack initiation site from the surface to the subsurface occurs. All fractured specimens were investigated with a scanning electron microscope (SEM). Large defects like primary intermetallic particles could not be found at the crack initiation sites. The difference between the subsurface non-defect crack initiation sites of both alloys is to be found in the fractographic structure. The internal crack initiation site of EN AW-6056-T6 shows a multiplicity of cleavage-like planes contrary to the flat area found at the alloy EN AW-6082-T5. These results were already presented in [1]. The scope of this present paper is new microstructural investigations and the formulation of a failure model which respects the results of different scales of microscopy. Electron back scatter diffraction analysis (EBSD analysis) and transmission electron microscopy (TEM) were done for both alloys to characterize the microstructure and to compare unstressed and tested materials. These differences are discussed with regard to the differences in failure mechanisms.

Mechanical engineering, Génie mécanique, 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, Alliage base titane, Titanium base alloys, Aluminium alliage, Aluminium alloy, Aluminio aleación, Aluminiumlegierung, Dislocation, Dislocación, Versetzung, Fatigue oligocyclique, Low cycle fatigue, Fatiga oligocíclica, Ermuedung bei niedrigen Lastspielzahlen, Haute température, High temperature, Alta temperatura, Hochtemperatur, Microstructure, Microestructura, Mikrogefuege, Propriété mécanique, Mechanical properties, Propiedad mecánica, Température, Temperature, Temperatura, Temperatur, Dislocations, High temperature fatigue, and Lamellar TiAl alloy

Low cycle fatigue properties of lamellar TiAl with 8 at.% Nb were studied at four temperatures: room temperature, 700, 750 and 800 °C. Up to 750 °C, stable cyclic behaviour is observed while cyclic softening is characteristic for 800 °C. The strength of the alloy is still high even at 800 °C. The TEM observation did not reveal any substantial changes in the microstructure due to the cycling at RT. At 750 °C, the lamellar structure was in some places destroyed by cyclic plastic straining and pure γ-phase islands with high density of dislocation debris were formed. At 800 °C, the domains without lamellar structure cover about 10% of volume and are almost dislocation free. The destruction of lamellar microstructure and possible annealing of dislocation debris is the reason for marked cyclic softening at 800 °C.

Mechanical engineering, Génie mécanique, 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 austénitique, Austenitic steel, Acero austenítico, Austenitischer Stahl, Basse température, Low temperature, Baja temperatura, Tieftemperatur, Déformation, Deformation, Deformación, Verformung, Fatigue, Fatiga, Ermuedung, Martensite, Martensita, Martensit, Microscopie électronique transmission, Transmission electron microscopy, Microscopía electrónica transmisión, Transmissionselektronenmikroskopie, Microstructure, Microestructura, Mikrogefuege, Propriété mécanique, Mechanical properties, Propiedad mecánica, Température ambiante, Room temperature, Temperatura ambiente, Raumtemperatur, Transformation martensitique, Martensitic transformation, Transformación martensítica, Martensitische Umwandlung, Transformation phase, Phase transformation, Transformación fase, Phasenumwandlung, Deformation induced martensite formation, Fatigue behavior, and TEM

Microstructural investigations of the fatigue behavior and phase transformation in the metastable austenitic steels AISI 304 and 348 were performed. The specimens were cyclically loaded with a constant total-strain-amplitude in the temperature range -60 °C to 25 °C. By means of stress-strain hysteresis and magnetic measurements, the fatigue behavior and phase transformation were characterized. Microstructural changes were evaluated by transmission electron microscopy and by scanning electron microscopy by means of electron backscatter diffraction technique at defined fatigue states. The steels show differences in austenite stability, which lead to significant changes in the deformation induced martensite formation and the fatigue behavior. Dependent on the type of steel and the testing temperature similar α'-martensite fractions but different strengths developed.