Teses / dissertações sobre o tema "Acier au manganèse – Propriétés thermomécaniques"
Crie uma referência precisa em APA, MLA, Chicago, Harvard, e outros estilos
Veja os 31 melhores trabalhos (teses / dissertações) para estudos sobre o assunto "Acier au manganèse – Propriétés thermomécaniques".
Ao lado de cada fonte na lista de referências, há um botão "Adicionar à bibliografia". Clique e geraremos automaticamente a citação bibliográfica do trabalho escolhido no estilo de citação de que você precisa: APA, MLA, Harvard, Chicago, Vancouver, etc.
Você também pode baixar o texto completo da publicação científica em formato .pdf e ler o resumo do trabalho online se estiver presente nos metadados.
Veja as teses / dissertações das mais diversas áreas científicas e compile uma bibliografia correta.
Lamari, Mathias. "In situ characterization and modelling of retained austenite thermomechanical stability in Medium Manganese Duplex TRIP-aided steels". Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0114.
Texto completo da fonteMedium manganese steels belong to the so-called 3rd generation of Advanced High Strength Steel (AHSS). Their ground-breaking properties are due to their particular duplex microstructures, which contain a micrometric “ferritic” matrix and a large amount of retained austenite. This new generation of steels is seen as one of the best possibilities for carmakers to continue improving the safety of light-duty vehicles and reduce their energy consumptions² and thus their environmental footprints. The good formability and the high resistance of those steels are explained by the strain-induced martensitic transformation (SIMT) of residual austenite during a mechanical loading. The gradual transformation of ductile austenite into high strength martensite causes a rapid increase in the macroscopic work-hardening of the steel, mechanism known as Transformation Induced Plasticity effect (TRIP). Understanding and modelling the stability of retained austenite and the related mechanical response of these steels are thus of great interest both from a scientific and industrial point of view.For this purpose, eight different microstructures have been designed based on thermodynamical calculations in order to evaluate the respective effect of the morphology, the composition and the grains size on austenite stability. The formation of the duplex microstructures during intercritical annealing have been characterized in situ by high-energy X-ray diffractions (HEXRD) experiments on synchrotron beamline. In addition to measuring austenitization kinetics using Rietveld refinements, these experiments reveal in an original way the mechanisms of primary precipitation/dissolution of carbides during heating and the large residual hydrostatic stresses at the scale of the phases obtained after final cooling. The origin of these latter has been explained and quantified through a model. An extensive scanning electron microscopy (SEM) and Castaing microprobe work was also conducted to measure the sizes and chemical compositions of the different microstructure components.The tensile mechanical behaviour of the studied steels has been measured in combination with HEXRD experiments and Digital Image Correlation (DIC) measurements. These unique in situ experiments permit to measure simultaneously the SIMT kinetics, the 3D stress partitioning between phases (namely ferrite, austenite and martensite) using sin²ψ methods and the local strains all along the tensile specimens. These latter serve in particular to characterize Lüders and Portevin-Le Chatelier (PLC) bands which affect the studied medium Mn steels.All those experimental inputs have served to develop an innovative mean field micromechanical framework to predict the tensile behaviour of medium Mn steels with austenite-ferrite-martensite microstructures. It relies on the description of the local behaviours of each constituting phase and of the SIMT of retained austenite, both calibrated on our HEXRD experiments. The work-hardening of austenite and ferrite are modelled thanks to a size-sensitive model based on dislocation densities. The behaviour of fresh and strain induced martensite is considered on the contrary as an extended elastic/plastic transition. The SIMT kinetics is based on a thermodynamical assessment of the stability of retained austenite inspired by Olson and Cohen pioneering work. The model is thus finally sensitive to the size of the microstructure components, to their local composition and to their respective stability and it shows an excellent agreement with the experimental observations
Bouchou, Abdelhake. "Modélisation du comportement de l'acier inoxydable 17 MoSPH sous sollicitations anisothermes entre 20 et 600c. Mise en évidence d'un effet d'histoire en température". Besançon, 1993. http://www.theses.fr/1993BESA2052.
Texto completo da fonteHernandez, Jean-François. "Comportement thermomécanique des bétons réfractaires et des revêtements monolithiques des poches a acier : influence de la déshydratation". Paris 6, 2000. http://www.theses.fr/2000PA066519.
Texto completo da fonteShi, Huiji. "Etude en fatigue thermomécanique sur un acier inoxydable : réalisation d'essais et prévision de la durée de vie du matériau". Metz, 1992. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/1992/Shi.Huiji.SMZ9214.pdf.
Texto completo da fonteLow cycle thermal mechanical fatigue tests were carried out on 316L stainless steel specimens. These tests were automatically controlled by a micro computer which permits to realize the superposition of thermal and mechanical cycles with the waveforms of out-of-phase and in-phase. Two temperature ranges (250° C-500°C and 250°C-650°C) of thermal cycling were controlled with the same waveform as the mechanical cycling. Both types of tests (in-phase and out-of-phase) were conducted at the same strain rate of 0,0001/s. The total strain range were realized from 1,0% to 2,4%. To predict the lifetime of components submitted to thermal mechanical fatigue, first the stress strain response of the material in stabilized cycles was simulated by a non linear kinematic hardening model. An internal variable was introduced into this model in order to describe the thermal cycling effect. With isothermal fatigue data this kinematic hardening model using three parameters depending on temperature and plastic strain range can correctly yields a very good approximation of hysteresis loop for low cycle thermal mechanical fatigue. To describe the influence of the variable tempetature on damage in thermal mechanical fatigue, a temperature damage factor was introduced. To study the fatigue damage process, a typical stabilized hysteresis loop of thermal mechanical cycling is considered to be the combination of great deal of parts, each of them corresponding to a given temperature, and a linear damage model based on the total strain energy density is supposed. This method using the isothermal fatigue data gives satisfactory results for thermal mechanical fatigue life prediction
Ahmer, Zeeshan. "An investigation on thermomechanical behaviour of a tool steel X38CrMoV5". Paris, ENMP, 2011. http://www.theses.fr/2011ENMP0075.
Texto completo da fonteHot work tool steel X38CrMoV5-47HRC is mainly used in industrial manufacturing processes such as high pressure die casting, hot Forging, stamping and rolling etc. The tools should comprise high fatigue strength as well as high toughness to defy thermal and mechanical shocks. The tool's Surface is principally ruined by the cyclic and progressive process under ephemeral temperature i. E. The process of non-isothermal fatigue. The appropriate constitutive laws are therefore required to predict the behaviour of material under non-isothermal conditions. This thesis depicts a contribution to predict the mechanical behaviour of X38CrMoV5-47HRC by numerical simulations using constitutive behaviour models. Assessment of the robustness and limitations of a Chaboche type thermoelastoviscoplastic model is carried out under several different test conditions starting from several uniaxial tests (LCF and TMF) to complex loading conditions with variable transient temperature range and variable amplitude of mechanical strain. After characterization of the model under the said conditions, its parameters have been re-identified in order to update the model to work under complex loading conditions. Keeping in view the model's limitations, further directions are also discussed in order to improve the model in terms of its application under severe loading conditions
Allain, Sébastien. "Caractérisation et modélisation thermomécaniques multi-échelles des mécanismes de déformation et d'écrouissage d'aciers austénitiques à haute teneur en manganèse : application à l'effet TWIP". Vandoeuvre-les-Nancy, INPL, 2004. http://docnum.univ-lorraine.fr/public/INPL_T_2004_ALLAIN_S.pdf.
Texto completo da fonteThe high manganese austenitic steels have a low stacking fault energy (SFE). Their plastic deformation is achieved by slip, but also by twinning or by [epsilon] martensitic transformation. Our thermochemical modeling including the Néel magnetic transition determines the value of the SFE and the deformation mechanisms activated as a function of the temperature and the composition. Tensile tests performed on Fe22MnO. 6C and 1. OC grades between 77 K and 673 K show that the homogeneous elongation is controlled by the work hardening rate through Considère's criterion. The best compromise between elongation and tensile strength is obtained at 298 K when twinning is activated (TWIP effect). At high temperature, the mere latent hardening leads to a low elongation and tensile strength. At low temperature, twinning is replaced by the [epsilon] martensitic transformation, gliding is thermally activated and the tensile strength is maximal. At 298 K, the TEM study reveals that twinning occurs by formation of microtwins gathered into stacks which are strong obstacles for dislocation gliding. Their thickness is determined by a 2D simulation at the scale of the dislocations. At the scale of the grains, two secant twinning systems are sequentially activated along with strain. Only the second twinning system, which appears at about 15 % strain, contributes efficiently to work hardening by reducing the mean free path of mobile dislocations. A crystal plasticity framework which is based on simple scale transition laws bas been developed. The viscoplastic behavior of each grain depends on the dislocation densities stored on each slip system. The activation of two twinning systems is triggered by a Schmid law and leads to a rapid decrease of the mean free path for the secant slip systems. The model well reproduces the link between the twinning microstructure and the mechanical properties
Rousseau, Claire. "Mise en évidence par échographie ultrasonore et thermographie infrarouge de correlations entre les évolutions de la microstructure et du bilan énergétique en plasticité pour un acier 304L". Montpellier 2, 2003. http://www.theses.fr/2003MON20203.
Texto completo da fonteHarzallah, Ridha. "Étude du comportement mécanique et tribologique des aciers austénitiques au manganèse : application aux cœurs de voies ferroviaires". Phd thesis, École Nationale Supérieure des Mines de Paris, 2010. http://pastel.archives-ouvertes.fr/pastel-00539563.
Texto completo da fontePiozin, Emma. "Influence des traitements thermomécaniques sur la microstructure et les propriétés mécaniques d'un acier à 9%Cr (Grade 91)". Thesis, Paris, ENMP, 2014. http://www.theses.fr/2014ENMP0049/document.
Texto completo da fonte9%Cr tempered martensitic steels are currently used in fossil power and in petrochemical plants. Due to attractive properties and manufacturing costs, there are also potential candidates for structural components of new generation nuclear reactors. To optimize their high temperatures mechanical properties (~500-650°C), a thermal-mechanical treatment based on “ausforming” is being considered. It is composed of an austenitization step, followed by warm-rolling of metastable austenite at intermediate temperatures (500-600°C), then quenching and tempering. This study aims at understanding the effects of each of these steps, and particularly the warm-rolling of the metastable austenite, on the resulting microstructure and mechanical properties.After applying a variety of thermal-mechanical treatment conditions, with or without warm rolling, the microstructures were systematically characterized at various scales by SEM, TEM, SANS, and neutron diffraction. Martensite laths are finer and dislocations density is higher in warm-rolled samples compared to thermally treated samples. In some cases, warm-rolled + tempered microstructures were partially recrystallized, showing that tempered martensite keeps a “memory” of previous rolling of metastable austenite. Contrary to what was expected, warm-rolling did not affect precipitation, which is principally governed by austenitizing and tempering temperatures.Warm-rolling lead to a remarkable increase in tensile and creep strength but strongly impairs ductility and significantly increases the ductile-to-brittle transition temperature. Some of the warm-rolled materials are sensitive to intergranular failure at both low (Charpy impact tests) and high temperature (creep tests). Moreover, warm-rolling of metastable austenite does not improve, and even increases cyclic softening. All microstructural features have been quantitatively linked to mechanical properties at 20°C, by applying a structural hardening model that could be reasonably transposed to predict yield and tensile strength at higher temperatures (i.e., 550°C and 650°C)
Robin-Boudaoud, Marie-Cécile. "Comportement et durée de vie de pièces tubulaires, soudées ou non, en acier ferritique 1. 4509 : application automobile". Paris, ENMP, 2010. http://www.theses.fr/2010ENMP0059.
Texto completo da fonteFaurecia uses stainless ferritic steels to produce car manifolds, which are made of several tubular parts welded together. In order to reduce design costs, Faurecia needs to developp a robust numerical design tool. In the frame of this project, this thesis is a contribution to fatigue life assessment of 1. 4509 stainless steel tubular parts, welded or not, submitted to cyclic thermomechanical loadings. In a first part, the cyclic mechanical behaviors of the base metal (1. 4509 steel) and the melted metal are experementally studied under various loads. They are then described thanks to an elastoviscoplastic model. The specific mechanical behavior of the heat affected zone is also considered. The ability of the proposed models to describe the mechanical response of a welded zone is assessed thanks to a traction compression test including local strain measurements. In a second part, fatigue life of 1. 4509 steel is adressed. A large experimental dabase is built up. A non isothermal continuum damage model (J. Lemaitre model) is identified. The same test conditions are applied to welded specimens. Then, the resuts of those tests are analysed thanks to an uncoupled approach of mechanical behavior and damage. It is so considered that the strain distribution at the stabilized cycle, governs the fatigue life of the welded specimen. Thanks to this method, most the tests are well predicted (within a scattering band of factor 3 maximum). Finally, last part of this thesis concerns the integration of the identified models in a robust numerical tool in order to predict fatigue life of industrial welded parts. A submodel methodology is used in order to precisely predict the stabilized mechanical behavior of welded zone. This technique is successfully applied to predict the fatigue life of two welded parts, included a car manifold
Samrout, Houssam. "Loi de comportement élastoviscoplastique à température variable d'un acier de disques de frein pour matériel ferroviaire". Bordeaux 1, 1996. http://www.theses.fr/1996BOR10663.
Texto completo da fonteConnesson, Nathanaël. "Contribution à l'étude du comportement thermomécanique de matériaux métalliques". Troyes, 2010. http://www.theses.fr/2010TROY0016.
Texto completo da fonteThermomechanical measurements are some-times performed to estimate fatigue limits and other mechanical properties of materials. How-ever, these empirical methods lack physical justification. What are the physical phenomena causing materials self-heating? What information can be obtained through thermal measurements? The aim of this work is to provide answers to theses questions. A precise dissipative energy measurement method (fields or spatially averaged dissipative energy) has been developed. A method to measure the plastic work per cycle (loading in tension-tension) has also been proposed. The thermomechanical characteristics of four materials (aluminum, ferritic steel, stainless steel and dual-phase steel) have then been studied. Much experimental data have been generated during this work, studying the energy behaviour of these materials during strain-hardening process (the aim was to establish an energy balance cycle by cycle) or simply studying the main characteristics of these materials dissipative energy in viscoelastic behaviour. Thus, the dissipative energy was usually proved insensitive to the strain rate, increased with the applied maximum stress, increased with plastic strain, was aging depend, etc. Theses experimental data could be used to feed mathematical models
tardif, nicolas. "Étude du comportement à haute température d'une fissuration instable dans l'acier 16MND5 et application au calcul de la rupture d'un fond de cuve en cas d'accident grave". Lyon, INSA, 2009. http://www.theses.fr/2009ISAL0105.
Texto completo da fonteHermant, Alexandre. "Evolutions microstructurales d’un acier inoxydable austénitique (316 Nb) au cours de sollicitations thermomécaniques représentatives de différents procédés de forgeage". Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEM081.
Texto completo da fonteMechanical properties and microstructure of 316Nb austenitic stainless steel may show some variability in hot forging products. This work aimed at improving knowledge about hot deformation mechanisms and microstructural evolution of this steel. Obtaining a homogeneous microstructure requires deep understanding of the hot deformation behaviour and mechanisms. In thick-walled components, both work hardening, dynamic recovery and recrystallization govern hot workability. Static and post-dynamic phenomena can induce further metallurgical evolution during interpass time and cooling. The influence of deformation temperature, strain, strain rate, cooling rate on recrystallization mechanisms has been studied by using hot torsion tests. Multiple-pass tests with isothermal and non-isothermal interpass allowed understanding post-dynamic mechanisms. Static phenomena were investigated using various annealing conditions. The effects of initial microstructural features such as grain size and chemical composition, specifically niobium solute content, on the hot deformation behaviour were eventually considered.The extent of dynamic recovery, coarse initial grain size, solute drag, and pinning of grain boundaries by fine Nb(C,N) particles strongly hinder dynamic recrystallization which does not dominate the metallurgical evolution over the range studied, in contrast to results reported on 316 steel. However, bulging of grain boundaries as a prelude to dynamic recrystallization was observed at low strains and high temperature. Grain boundary serrations progressively lead to the formation of subgrain boundaries, then of new high angle boundaries. A particular dynamic recrystallization mechanism explains progressive elimination of annealing twins. Interaction with dislocations depends on locally activated slip systems and whether they are common to both twin and parent grain. At moderate strain levels, post-dynamic recrystallization occurs by rapid growth of nuclei that depends on deformation temperature, and applied strain and strain rate. For a given chemical composition, neither dynamic nor post-dynamic recrystallization is affected by the initial grain size over the range studied. Increasing the free niobium content promotes solute drag and niobium carbide precipitation, which significantly delay recrystallization. The microstructure after annealing essentially depends on the availability of solute atoms such as niobium and on residual δ-ferrite. Nb(C,N) precipitates formed during hot deformation do not significantly influence recrystallization kinetics
Béreyziat, Antoine. "Étude du comportement thermomécanique de poutres mixtes acier-bois en situation d’incendie". Thesis, Ecully, Ecole centrale de Lyon, 2022. http://www.theses.fr/2022ECDL0005.
Texto completo da fonteTimber-steel hybridization has great potential, because steel and timber component can reinforce each other, timber can be used to protect steel from fire, and the non-combustibility of steel can be used in an advantageous way. However, this form of hybridization is not widespread despite recent developments in the use of timber for multi-story buildings. Therefore, it is proposed to study composite beams made from timber and steel combined in such a way that the best possible performances are achieved, in normal and fire situations. Firstly, behavior of steel and timber is described in normal and fire situations. A description of wood combustion is proposed to better understand what underlies the temperature dependence of its properties. A focus is made on the mass transfer that occur into timber as it burns. Then, the timber-steel hybridization is addressed through an overview. Afterward, a literature review is made on a specific configuration type, which is assembled by inserting timber beams between the flanges of a hot-rolled “I” profile, while ensuring that this profile is protected from fire by timber. The description of the elastic behavior of studied beams in normal situation is achieved using the gamma method. Bending tests on hybrid beams and their components corroborate this analytical model, but an unexpected composite behavior is observed when steel yielding begins. Thus, a significant strength gain results from the combination of timber and steel. We manage to simulate this behavior by increasing the yield point of the modeled steel compared to the measured value, as well as the tensile strength of timber. Then, fire tests on unloaded specimens are performed. On this occasion, we confirm that correct temperature measurements into timber require orienting thermocouples parallel to isotherms. Many configurations are compared, which allows to understand in detail the effectiveness of the fire protection provided by wood to steel profiles. Mass transfers that occur into timber appear to have a significant effect on temperatures measured on protected steel profiles. The comparison of measured and simulated temperatures allows to highlight the importance of tightness of assembly joints during exposure to fire. Wood combustion and steel temperatures are observed after the end of the fire exposure, and the behavior of hollow configurations is contrasted with that of the timber filled configurations. Finally, fire tests on mechanically loaded beams show that a steel profile protected using 45 mm thick timber components can resist fire for 81 min. Thus, R60 is exceeded with relatively thin protection. Results show that the loading has an impact on steel temperatures, because of an opening of the assembly joints. Numerical simulations show that timber gives fire resistance of the composite beam both thermally and mechanically, by protecting the steel profile, but also by relieving its load. This work shows the effectiveness of steel-timber composite beams, in normal and fire situations, and contributes to the understanding of their behavior. However, proposals for improvement and new challenges are formulated, opening prospects for the study and use of these composite beams
García, Aranda Maria Lucia. "Etude thermomécanique et modélisation numérique de l'emboutissage à chaud de l'Usibor 1500". Paris, ENMP, 2004. http://www.theses.fr/2004ENMP1268.
Texto completo da fonteCostes, Frédéric. "Modélisation thermomécanique tridimensionnelle par éléments finis de la coulée continue d'aciers". Phd thesis, Paris, ENMP, 2004. http://www.theses.fr/2004ENMP1267.
Texto completo da fonteBouslah, Mounia. "Elaboration et caractérisation d'une mousse syntactique à base de résine phénolique pour la protection de conduites en acier dans l'industrie pétrolière". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEC014/document.
Texto completo da fonteThis work consisted in the development and the evaluation of a phenolic syntactic foam performance for the production of a multilayer sandwich system (core/skin in composite material). It ensures thermal, mechanical and fire protection, in particular against the impact of a jet fire. A jet fire can occur on a petrochemical site resulting from the combustion of a fuel continuously released under pressure. It can be very devastating for its abrasive effect and intense convective and radiative flux. The work focuses mainly on the study of the effectiveness of the phenolic syntactic foam through the analysis of the relationship microstructure-propriety. The manufacturing process requirements imposed to control the elaboration via a good understanding of the reactivity of the resin, especially in relation to various physical transformations (gelation, vitrification) that take place during the curing mechanisms. That involves optimizing the proportions of the various active compounds and additives depending on the working conditions in order to achieve optimal properties of the final material. The effectiveness of this final material under normal conditions of use was determined by a complete testing phase on its mechanical, thermal and thermomechanical properties. Fire tests were also conducted to investigate the material burning behavior to ensure its protective properties under a jet flame impact. Finally, a large-scale instrumented test, reproducing in real conditions a propane gas leak at high pressure, was developed to evaluate the resistance to a jet fire of a complete industrial prototype. In parallel, a simplified numerical model was also proposed to simulate the impact of such a fire
Costes, Frédéric. "Modélisation thermomécanique tridimensionnelle par éléments finis de la coulée continue d'aciers". Phd thesis, École Nationale Supérieure des Mines de Paris, 2004. http://pastel.archives-ouvertes.fr/pastel-00001334.
Texto completo da fonteMarchal, Arnault. "Comportement thermomécanique d'aciers déformés par essais de torsion à chaud". Vandoeuvre-les-Nancy, INPL, 1997. http://www.theses.fr/1997INPL013N.
Texto completo da fonteArlazarov, Artem. "Évolution des microstructures et lien avec les propriétés mécaniques dans les aciers 'Médium Mn'". Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0086/document.
Texto completo da fonteDuring the intercritical annealing of fully martensitic Medium Mn steel, containing from 4 to 12 wt.% Mn, the formation of austenite happens through the so-called “Austenite Reverted Transformation” (ART) mechanism. In this PhD work, the evolution of both microstructure and tensile properties was studied as a function of holding time in the intercritical domain. The microstructure evolution was studied using a double experimental and modeling approach. The final microstructure contained phases of different natures (ferrite (annealed martensite), retained austenite and fresh martensite) and of different morphologies (lath-like and polygonal). A particular attention was paid to the kinetics of austenite formation in connection with cementite dissolution and to the morphology of the phases. A mechanism was proposed to describe the formation of such microstructure. The critical factors controlling thermal austenite stability, including both chemical and size effects, were determined and discussed, based on the analysis of the retained austenite time-evolution. At last, tensile properties of the steel were measured as a function of holding time and the relation between microstructure and mechanical behavior was analyzed. Advanced analysis of the individual behavior of the three major constituents was performed. As a final output of this work, a complete model for predicting the true-stress versus true-strain curves of medium Mn steels was proposed
Lavisse, Bruno. "Approche thermomécanique de l’interface meule/pièce/lubrifiant lors de la rectification de dentures d'engrenage en acier nitruré : impacts sur l’intégrité du matériau rectifié". Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0190.
Texto completo da fonteThe grinding process is very useful to obtain a very precise surface finish. It is generally used on very hard materials which cannot be machined by other conventional machining processes. However grinding involves very complex material removal mechanisms and most of the time is difficult to set up. During the grinding process, the main grinding energy is converted into heat between chip, lubricant, wheel and workpiece. Temperature and heat flux in the grinding zone depend on the contact geometry, on the material, on the wheel (grit size, geometry, porosity, wear), on the dressing, on the grinding parameters (depth of cut, workpiece speed, wheel speed) and on lubrication conditions. High temperatures result in thermal damage such as metallurgical changes, stress gradients, and changes in workpiece dimensions. In general terms, because of this process, surface integrity may be seriously damaged. Grinding parameters have to guarantee the workpiece quality and have to respond to the productivity improvement in machining and cutting industry. The target of this thesis was the mechanical and thermal study of the grinding zone between workpiece, wheel and lubricant in order to reduce the burn risk during the grinding of a nitrided steel gear. The purpose was also to define possible transformations associated to this damage. To achieve it, we developed several research topics. We proposed an experimentally verified heat flux model, usable to predict accurately the nitrided steel temperature in the lubricated grinding zone. This model is based on an inverse method and temperature measurements with a workpiece/foil thermocouple. We made a grinding wheel comparative study in order to determine the wheel capable, for a given workpiece roughness, of limiting the risk of burn. To perform this study, we focused, for each wheel, on the maximum allowable depth of cut before burning. This comparative study was led both in laboratory and industrial conditions. We also studied the influence of thermal damages in grinding by studying and qualifying the nitrided steel microstructure. The use of classical measurement techniques such as: hardness, SEM, EBSD and DRX or original and underused techniques such as Barkhausen noise or Raman spectroscopy permitted to define changes in the burned grinded materials. Between the two states of materials (burned and no burned), we observed differences in hardness, grain size and ferrous oxides creation. At last, we made a detailed study on the lubrication efficiency during grinding of the nitrided steel. For this purpose we changed independently fluid flow and jet speed in outlet nozzle. Then we observed the modifications this could cause on the temperature distribution in the grinding zone and on the workpiece heat partition ratio
Louche, Hervé. "Analyse par thermographie infrarouge des effets dissipatifs de la localisation dans des aciers". Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 1999. http://tel.archives-ouvertes.fr/tel-00259398.
Texto completo da fonteA partir d'un traitement d'images thermiques infrarouge (effets) et de l'équation de diffusion de la chaleur, on propose une méthode permettant d'estimer les sources de chaleur (causes) générées par le processus de déformation.
Sur certains aciers doux, on met en évidence la propagation à vitesse uniforme d'une ou plusieurs bandes dissipatives étroites à travers la zone utile de l'éprouvette. Comparativement à ce premier mode (bandes de Lüders) où les effets dissipatifs sont soudains, intenses et très localisés, on met en évidence le caractère plus régulier et progressif de la concentration des zones où se développent les irréversibilités mécaniques menant à la striction localisée. Des "indicateurs de localisation énergétiques'' proposés pour détecter la localisation montrent qu'elle peut apparaître avant le maximum de la charge, dans plusieurs zones de l'éprouvette. Ce constat implique que la partie utile d'une éprouvette doit être considérée comme une structure et non comme un élément de volume réagissant de façon homogène, ce qui n'est pas sans conséquences sur les méthodes d'identification des modèles de comportement utilisés, en particulier, dans les approches théoriques de la localisation.
Enfin, d'autres expériences ont permis de mettre en évidence des manifestations énergétiques associées à des formes particulières de localisation : propagation de fronts de changement de phase (acier inoxydable A301), effets dissipatifs associés à des bandes de glissement (acier magnétique HiBiGO), effets dissipatifs localisés dans des bandes de cisaillement (polymère PVC).
Caruso, Matteo. "Thermomechanical processing of eutectoid steels: strategies to improve the microstructure of the hot rolled strips". Doctoral thesis, Universite Libre de Bruxelles, 2013. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209371.
Texto completo da fonteexcellent strength levels and wear resistance. These properties arise from the unique morphology of lamellar pearlite which can be considered
as a self-laminated nanoscale composite. However, a spheroidization annealing step is nowadays necessary to improve the cold forming properties before further cold rolling steps.
This thesis is aimed at improving the tensile ductility of the hot rolled products of eutectoid composition in order to eliminate the intermediate
annealing step. Two strategies are proposed.
The first is to transpose the concept of controlled rolling developed for HSLA to
eutectoid steels. Through a strict adjustment of the austenite processing and of the cooling strategy, it is possible to improve the ductility
of the final lamellar microstructure. The way the processing parameters influence the hot deformation of austenite, the eutectoid transformation and of the subsequent spheroidization annealing is deeply
investigated. It is found that refinement and pancaking of austenite
is beneficial as it reduces the pearlite block size improving the total
tensile elongation. Accelerated cooling is of paramount importance to
achieve fine Interlamellar spacing (ILS), which lead to high strength
levels and accelerate spheroidization during subsequent annealing.
The second approach involves intercritical or warm deformation. Warm processing of eutectoid steels is first explored by torsion testing
and then up-scaled to a pilot rolling-line. The interactions between thermomechanical parameters, rolling forces generated and microstructural
evolution are carefully scrutinized. During concurrent hot deformation, spheroidization of cementite takes place almost instantaneously
in both torsion and rolling. The restoration processes occurring in the ferrite matrix depends on the strain path and the strain rates. Low strain rates (0,1 s−1) and simple shear promotes the formation of a recrystallized-like HABs network of about 3μm in size.
Plane strain compression and high strain rates (10 s−1) leads to the formation of a typical recovered dislocation substructure (LABs) of 1μm in size. During annealing, no recrystallization occurs and the LABs substructure remains stable. This substructure influences drammatically the mechanical properties: the strength is very high and the work-hardening behavior is poor due to high recovery rate in the region close to the LABs. However, due to the presence of spheroidized
cementite particles the ductility of warm rolled eutectoid steels is higher than that of ultra fine grained low carbon steels.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
Brunel, Florent. "Étude thermomécanique du couple roue-semelle ferroviaire sous sollicitations de freinage". Lille 1, 2007. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2007/50376-2007-77.pdf.
Texto completo da fonteUne seconde modélisation est proposée permettant la prise en compte de la géométrie 3D de la semelle. L'originalité se situe dans la résolution thermique transitoire de la roue, basée sur un suivi temporel d'une section de roue suivie d'une reconstitution 3D. Les résultats permettent la prédiction des localisations sur toute la surface de frottement. L'utilisation conjointe de ces modèles permet de répondre à l'objectif de prédiction des gradients thermiques et de mise à disposition de moyens d'optimisation de la semelle. Pour le second objectif de prédiction de l'évolution des contraintes résiduelles dans les roues, la détermination de l'état initial, issu du traitement thermique, est nécessaire. Elle est réalisée à l'aide d'un modèle thermomécanique 2D axisymétrique. Le coefficient d'échange thermique, lors de la trempe, a été identifié sur un dispositif expérimental développé spécifiquement. Différentes simulations ont pu montrer l'importance du modèle de comportement du matériau de la roue sur la distribution des contraintes résiduelles, notamment la prise en compte des phénomènes visqueux. Les résultats indiquent une bonne prédiction de l'évolution des contraintes résiduelles, de compression après le traitement thermique puis leur passage en traction après freinages, en conformité avec les relevés expérimentaux. Des compléments sont en cours pour une meilleure identification du modèle de comportement du matériau de la roue
Karch, Abdellatif. "Étude des évolutions microstructurales lors de la transformation à chaud d’aciers ferritiques renforcés par dispersion d’oxydes". Thesis, Paris, ENMP, 2014. http://www.theses.fr/2014ENMP0075/document.
Texto completo da fonteThe production of ODS steels involves a powder consolidation step usually using the hot extrusion (HE) process. The anisotropic properties of extruded materials, especially in the ODS ferritic grades (>wt%12Cr), need a better understanding of the metallurgical phenomena which may occur during HE and lead to the observed microstructure. The hot working behavior of these materials is of particular interest. The methodology of this work includes the microstructure analysis after interrupted hot extrusion, hot torsion and hot compression (1000-1200°C) tests of ferritic steels with 14%Cr and different amounts in Ti and Y2O3.The microstructure evolution during hot extrusion process is associated with continuous dynamic recrystallization (CDRX). It leads to the creation of new grains by the formation of low angle boundaries, and then the increase of their misorientation under plastic deformation. The investigations highlight also the role of precipitation on the kinetics of this mechanism; it remains incomplete in the presence of fine and dense nanoprecipitates. After hot deformation in torsion and compression, it is noticed that both precipitates and temperature deformation have a significant impact on the deformation mechanisms and microstructure evolution. Indeed, the CDRX is dominant when temperature and amount of reinforcement are limited. However, when they are increased, limited microstructure evolution is observed. In this case, the results are interpreted through a mechanism of strain accommodation at grain boundaries, with low dislocation activity in the bulk of the grains
Mouelle, Loïc. "Caractérisation et modélisation d’assemblages de tôles en acier inoxydable austénitique brasées et soudées pour des applications d’échangeurs de chaleur". Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0068.
Texto completo da fonteThe aim of the study relies on an industrial context, in which, high pressure Plate Fin Heat Exchangers (PFHE) made of austenitic stainless steel 316L, are brazed with Ni-Cr-Fe-Si (BNi-5) alloy, then followed by dissimilar multipass TIG (Tungsten Inert Gas) welding process with nickel-based superalloy Inconel 625, used as filler metal. Due to their heterogeneous microstructure and chemical composition, fractures of brazed joints may appear during the welding of brazed assembly. Firstly, microstructural and chemical characterizations are made at the bonding interface between base metal, brazed joints and weld beads, to understand the fracture phenomena. Results show that a brazing cycle promoting the formation of γ-Ni single phase brazed joints, allows avoiding the fracture of brazed joints during welding. However, intergranular Si may involve the formation of hot cracks in brazed joints located in HAZ. The study of GOS (Grain Orientation Spread) through EBSD measurements, allows quantifying the magnitude and spatial distribution of plastic deformation in the HAZ after welding. A welding energy under 1100 J/mm limits the plastic deformation of brazed assemblies. Nanoindentation and tensile tests are also carried out at room temperature to determine the mechanical properties of brazed assembly. The results of tensile tests show that fracture occurs in the 316L, when brazed joints are formed by a γ-Ni single phase. Secondly, an original thermodynamically consistent modeling approach, dedicated to welding applications, is presented to describe the phenomenon of hardening recovery in metals during annealing heat treatment. The constitutive equations are based on a classical thermo-elasto-plastic formulation which is enhanced by a new recovery variable counterbalancing the effect of the hardening through a temperature-dependent evolution law. The model is implemented into the FE solver ABAQUS/Standard with the help of a User Material subroutine (UMAT). The identification of the model parameters is achieved through experimental compressive tests and heat treatments on 316L austenitic stainless steel. In addition, to evaluate the capabilities of the model, residual stress measurements are carried out on a welded plate and compared to values computed by numerical simulation. The obtained values match the experimental measurements. Finally, three-dimensional simulations of multipass welding are realized to estimate the stress and deformation fields during TIG welding process of a heat exchanger. The maximum stress in HAZ may reach 600 MPa during the cooling of the first welding pass. Thus, the results of numerical simulation are in agreements with the experimental observations, indicating that in case of fracture of brazed joints during welding, the fracture occurs from the cooling of the first passes
Kpenyigba, Kokouvi Mawuli. "Étude du comportement dynamique et modélisation thermoviscoplastique de nuances d'acier soumises à un impact balistique". Thesis, Université de Lorraine, 2013. http://www.theses.fr/2013LORR0272/document.
Texto completo da fonteThis thesis aims to contribute to the study of the thermo-mechanical behaviour of metallic materials subjected to ballistic impact. Experimental, analytical and numerical studies were performed to analyze in details the process of perforation. Two materials have been investigated in this work : mild steel ES and IF steel. As a first step, mechanical characterization tests (tensile and compression tests under quasi-static and dynamic conditions) As have been made towards to modeling the mechanical behaviour of the materials studied. The results show that mild steel ES and IF steel are highly susceptible to the strain rate. Two constitutive equations, one empirical (Johnson-Cook) and other semi-physical (Rusinek-Klepaczko) were used to model the thermoviscoplastic behaviour of materials. A complete identification of constants defining the two models was carried out for each material in order to implements the constitutive laws into a finite element code for the numerical simulation of impact and perforation tests. The behaviour of materials under impact was then examined. The effect of the projectile shape, the mechanical properties of the projectile material, the target thickness and it is configuration (monolithic or sandwich) on the perforation process was analyzed. The results show that the failure mode, the ballistic limit and the energy absorption power of the metal target are strongly related to the shape of the projectile used. It has been shown that the monolithic targets plates are more strong to be perforate than the sandwich configurations (total thickness less than or equal to 4 mm). In addition, it was found that the ballistic limit of the target is strongly influenced by the rigidity of the projectile used. Finally, a 3D FE model was developed to simulate the mechanical behaviour of metal targets subjected to ballistic impact. The results from the numerical predictions were compared with experiments. It has been observed globally a good agreement between the numerical predictions and experiments especially in terms of ballistic curves, energy absorbed, failure modes and failure time for each kind of projectile. The numerical results show the importance of an accurate description of materials behaviour under dynamic conditions based on laboratory experiments including thermal softening effects, strain hardening and strain rate sensitivity in numerical modeling of physical processes
Srikunwong, Chainarong. "Modélisation du procédé de soudage par points". Phd thesis, École Nationale Supérieure des Mines de Paris, 2005. http://tel.archives-ouvertes.fr/tel-00151464.
Texto completo da fontede soudage, la difficulté principale en simulation numérique est la disponibilité de données d'entrée à toutes températures depuis l'ambiante jusqu'au-delà de la fusion. Le couplage des premiers modèles électrothermiques avec des modèles mécaniques permet un bon accord entre expérience et simulation. Une fois qu'un modèle a été validé selon tous les domaines physiques concernés, des résultats comme les cycles thermiques, la taille de soudure ou les contraintes, déformations et état métallurgique résiduels peuvent être utilisés pour mieux comprendre le procédé, pour le piloter ou pour modéliser le comportement des soudures.
Dumay, Alexis. "Amélioration des propriétés physiques et mécaniques d'aciers TWIP FeMnXc : influence de la solution solide, durcissement par précipitation et effet composite". Thesis, Vandoeuvre-les-Nancy, INPL, 2008. http://www.theses.fr/2008INPL014N/document.
Texto completo da fonteTWIP steels deformation occurs by twinning and by dislocations gliding which leads to high a strain hardening. The deformation mechanisms are controlled by the stacking fault energy (SFE). A model for the prediction of the SFE and a law for TNéel (antiferro to paramagnetic transition) for austenite are proposed in FeMnXC systems (X = Cu, Cr, Al, Si et Ti). The studied FeMnCuC grades have a lower SFE than the Fe22Mn0,6C reference. The formation of [epsilon]-martensite replaces twinning without any deterioration of the mechanical properties. The flow stress decreases with the carbon content and the formation of [alpha]'-martensite at the lowest SFEs reduces the elongation to fracture. Substituting a part of the manganese content by copper leads to a 20% increase of the Young's Modulus at room temperature by decreasing TNéel below 0ºC. The precipitation of intragranular vanadium carbide increases the yield stress but does not influence the strain hardening rate. No interaction between precipitates and twins has been observed by microscopy. The coherency calculations and the TEM observations show that the carbides have an orientation relation with the austenite and are semi-coherent with a low residual coherency. The resulting stresses do not seem to be high enough to trap large quantities of hydrogen. The FeMnC + TiC alloys exhibit a strong hardening by composite effect at the beginning of deformation, while the strain hardening due to TWIP effect is not modified by the presence of the TiC particles. Meanwhile, cleavage occurs in the largest primary precipitates, which reduces the elongation to fracture
Caisso, Camille. "Caractérisation et modélisation de la rupture dans le domaine de la transition ductile-fragile de matériaux tubulaires utilisés dans la fabrication de générateurs de gaz pour airbags". Thesis, Brest, École nationale supérieure de techniques avancées Bretagne, 2021. http://www.theses.fr/2021ENTA0014.
Texto completo da fonteThis work deals with the characterization of the ductile and brittle failure mechanisms of tubular materials used for the manufacture of airbag gas generators. During a crash, airbag cushion is inflated in a few milliseconds by a gas generator. In case of gas generator failure, a ductile failure mode must be ensured up to temperatures of -60°C. A Charpy ring test has been proposed to quantify the risk of brittle failure of gas generator materials. However, this modification of the Charpy test raises two issues: to what extent does this test allow to characterize the ductile-fragile transition and how can the risk of brittle failure of an operating gas generator be deduced from the results of the Charpy test? To answer these questions, an approach combining experiments and numerical simulations was implemented. Various experimental configurations were developed in order to characterize material behavior and ductile damage. The ductile failure is modeled with a local approach. Then, ductile to brittle transition was characterized by a Charpy ring test campaign performed for temperatures between -160°C and 23°C. A numerical study of this test was carried out. Coupled with the Charpy tests, it allowed to set up a model of the brittle failure. The risk of gas generators brittle failure is finally evaluated. The influence of the manufacturing process on the risk of brittle failure was also studied