Une nouvelle approche des conséquences thermomécaniques induites par les procédés d'usinage : application à la rectification et au tournage

Les sollicitations thermomécaniques locales et les changements métallurgiques sont les principaux phénomènes à l'origine de l'apparition des contraintes résiduelles induites par les opérations d'usinages. Les études réalisées dans ce domaine font intervenir des modèles éléments finis simulant la coupe. Ceux ci sont très difficiles à mettre en oeuvre du fait des incertitudes des coefficients de frottement interfaciaux, des modèles d'endommagement et de l'ensemble des paramètres numériques. La méthode présentée dans cet article permet de s'affranchir de la simulation de l'enlèvement de matière et a pour but de simuler les contraintes résiduelles dans la profondeur de la pièce en fonction des paramètres d'usinage utilisés. Dans cette méthode, l'approche faite des procédés d'usinage est plus globale et peut donc s'appliquer aussi bien sur des procédés de coupe (tournage) que d'abrasion (rectification). Le détail de la méthode ainsi qu'une application aux procédés de tournage et de rectification est donné dans cette article

Effects of toolpath and clamping strategies in machining distortion of stainless-steel parts

Heat exchangers in new nuclear power generation plants are made of thin AISI 316L stainless-steel plates stacked together in order to improve their efficiency and compactness. To ensure the assembly, the global distortion of those plates must be mastered and minimized, mainly by predicting the evolution of the residual stress field during their manufacturing process chain. During machining, those residual stresses are redistributed to reach another equilibrium state, leading to a macroscopic part distortion. The main objective of this work is to study experimentally the influence of the machining toolpath and clamping strategies on the global part distortion. Then, a part distortion model is developed in order to verify the clamping effect on the distortion

Instrumented clamping device and numerical simulations to study machining distortion

Machining part distortion is due to residual stresses induced by previous manufacturing processes. This study aims to evaluate the influence of machining conditions on AISI 316L plate distortion. Therefore, a special experimental device with force sensors integrated in the clamping system and numerical model of distortion were developed. Residual stresses due to previous machining processes were measured using a layer removal method and neutron diffraction technique. Then, distributions of these residual stresses were integrated in a developed model of machining distortion, which considers the clamping and machining sequence effects after each stage of the toolpath. A comparison of the experimental and numerical results revealed that the finite element method can adequately predict machining distortion. The results also suggest that clamping and machining sequence can affect part distortion

MODÉLISATION EXPÉRIMENTALE ET NUMÉRIQUE DES EFFETS INDUITS PAR LA RECTIFICATION. APPLICATION À LA RECTIFICATION HAUTE PRODUCTIVITÉ

Grinding is one of the most complex material removal processes where many domains of physics take place. Nowadays, studies on grinding are still to be improved even if it is often used for manufacturing high-quality parts. Indeed, during grinding, many phenomena can appear such as burns or cracks that can affect the integrity of the ground surface and need to be controlled. They are linked to the amount of thermal and mechanical energy that enter the workpiece. Thus, in order to improve the grinding process and its productivity, ameliorations have to be made concerning measurements and predictions of such phenomena. In this work, the use of current measurement methods such as thermography for temperature or X-ray diffraction for residual stresses help to improve the models of grinding. Many results with better accuracy are shown and they explain the relation between the grinding parameters and the damage of the surface. Numerical simulation is the other way of understanding and predicts damage for the grinding process. The metallurgical transformations that can appear during grinding are taken into account and an inverse method is used for the modeling of thermo-mechanicals loads entering the workpiece.La rectification est un procédé de fabrication indispensable à la réalisation de pièces nécessitant des états de surface de qualité. C'est aussi un des procédés les plus complexes car il fait intervenir de nombreux domaines de la physique dont les interactions sont aujourd'hui encore mal maitrisées. Ainsi, plusieurs endommagements (brûlures, fissures,...) générés par le contact de la meule sur la pièce usinée peuvent apparaître. Ces phénomènes liés aux apports d'énergie thermique et mécanique de la meule à la pièce ont des origines diverses (transformations métallurgiques, dilatation ...). Dans un souci d'optimiser ou d'améliorer la productivité du procédé de rectification, la mesure, la compréhension et la prédiction de ces phénomènes sont alors nécessaires. Dans ces travaux, de nombreux axes de recherche autour du procédé de rectification sont traités. L'utilisation de techniques actuelles comme la mesure de température par thermographie ou de contraintes résiduelles par diffraction des rayons X a permis de déterminer de nouveaux modèles expérimentaux. Ces résultats montrent notamment le faible effet de la lubrification sur la température maximale atteinte pendant le procédé. La prédiction des endommagements passe ensuite par la simulation par éléments finis du procédé. Face aux différents chargements thermodynamiques présents au niveau du contact entre meule et pièce, une approche globale est utilisée couplée avec une méthode inverse sur les résultats expérimentaux. L'originalité est également apportée par la prise en compte numérique des transformations métallurgiques ce qui s'est révélé comme indispensable pour une modélisation proche de la réalité

Modélisation expérimentale et numérique des effets induits par la rectification (Application à la rectification haute productivité)

ST ETIENNE-ENS des Mines (422182304) / SudocST ETIENNE-ENISE (422182303) / SudocSudocFranceF

Une nouvelle approche des conséquences thermomécaniques induites par les procédés d'usinage : application à la rectification et au tournage

Colloque avec actes et comité de lecture. Internationale.International audienceLes sollicitations thermomécaniques locales et les changements métallurgiques sont les principaux phénomènes à l'origine de l'apparition des contraintes résiduelles induites par les opérations d'usinages. Les études réalisées dans ce domaine font intervenir des modèles éléments finis simulant la coupe. Ceux ci sont très difficiles à mettre en oeuvre du fait des incertitudes des coefficients de frottement interfaciaux, des modèles d'endommagement et de l'ensemble des paramètres numériques. La méthode présentée dans cet article permet de s'affranchir de la simulation de l'enlèvement de matière et a pour but de simuler les contraintes résiduelles dans la profondeur de la pièce en fonction des paramètres d'usinage utilisés. Dans cette méthode, l'approche faite des procédés d'usinage est plus globale et peut donc s'appliquer aussi bien sur des procédés de coupe (tournage) que d'abrasion (rectification). Le détail de la méthode ainsi qu'une application aux procédés de tournage et de rectification est donné dans cette article

Effect of a Vortex Distortion on the Operability of an Ultra High Bypass Ratio Fan

Inlet distortion can significantly impact turbofan operability. In the present contribution, the focus is on vortex ingestion, which is a type of distortion that has received less attention in the literature for high-bypass-ratio fans of civil engines than in- let separation or boundary layer ingestion. Due to the unsteady and non-axisymmetric nature of the inflow, full annulus computations are performed, using an unsteady RANS approach with a sliding mesh interface between the rotor and the stator. The goal is to provide a detailed analysis and understanding of the mechanisms responsible for operability loss when a vortex is ingested by the fan. To that end, a simplified model of vortex is derived from previous simulations in crosswind conditions including the presence of the ground plane. The study test case is a turbofan demonstrator representative of modern turbofans. Simulations are run with and without vortex at several operating points until rotating stall is observed. The global results show that the vortex ingestion induces a stall margin loss of up to 8%. Modal analysis indicates a stall pattern with 10 cells rotating at somewhere between 52 and 67% of the shaft speed. A comparison of the two configurations shows that the stall inception mechanism is similar with and without distortion. In particular, examining the incidence at the fan blade, a similar critical angle is observed for the two configurations, which is leveraged to establish a stall criterion valid for vortex ingestion cases

Simulation of a Potential CO2 Storage in the West Paris Basin: Site Characterization and Assessment of the Long-Term Hydrodynamical and Geochemical Impacts Induced by the CO2 Injection

This article presents the preliminary results of a study carried out as part of a demonstration project of CO2 storage in the Paris Basin. This project funded by ADEME (French Environment and Energy Management Agency) and several industrial partners (TOTAL, ENGIE, EDF, Lafarge, Air Liquide, Vallourec) aimed to study the possibility to set up an experimental infrastructure of CO2 transport and storage. Regarding the storage, the objectives were: (1) to characterize the selected site by optimizing the number of wells in a CO2 injection case of 200 Mt over 50 years in the Trias, (2) to simulate over time the CO2 migration and the induced pressure field, and (3) to analyze the geochemical behavior of the rock over the long term (1,000 years). The preliminary site characterization study revealed that only the southern area of Keuper succeeds to satisfy this injection criterion using only four injectors. However, a complementary study based on a refined fluid flow model with additional secondary faults concluded that this zone presents the highest potential of CO2 injection but without reaching the objective of 200 Mt with a reasonable number of wells. The simulation of the base scenario, carried out before the model refinement, showed that the overpressure above 0.1 MPa covers an area of 51,869 km2 in the Chaunoy formation, 1,000 years after the end of the injection, which corresponds to the whole West Paris Basin, whereas the CO2 plume extension remains small (524 km2). This overpressure causes brine flows at the domain boundaries and a local overpressure in the studied oil fields. Regarding the preliminary risk analysis of this project, the geochemical effects induced by the CO2 injection were studied by simulating the fluid-rock interactions with a coupled geochemical and fluid flow model in a domain limited to the storage complex. A one-way coupling of two models based on two domains fitting into each other was developed using dynamic boundary conditions. This approach succeeded to improve the simulation results of the pressure field and the CO2 plume as well as the geochemical behavior of the rock. These ones showed that the CO2 plume tends to stabilize thanks to the carbonation in calcite and dawsonite and no significant porosity change appears over 1,050 years. The CO2 mass balance per trapping type gives a CO2 carbonation rate of about 78% at 1,050 years that seemed to be excessive compared to the simulation study of other storage sites. Thus, an additional work dealing with both the kinetic data base and the textural models would be necessary in order to reduce the uncertainty of the injected CO2 mineralization

Simulation of a Potential CO

This article presents the preliminary results of a study carried out as part of a demonstration project of CO2 storage in the Paris Basin. This project funded by ADEME (French Environment and Energy Management Agency) and several industrial partners (TOTAL, ENGIE, EDF, Lafarge, Air Liquide, Vallourec) aimed to study the possibility to set up an experimental infrastructure of CO2 transport and storage. Regarding the storage, the objectives were: (1) to characterize the selected site by optimizing the number of wells in a CO2 injection case of 200 Mt over 50 years in the Trias, (2) to simulate over time the CO2 migration and the induced pressure field, and (3) to analyze the geochemical behavior of the rock over the long term (1,000 years). The preliminary site characterization study revealed that only the southern area of Keuper succeeds to satisfy this injection criterion using only four injectors. However, a complementary study based on a refined fluid flow model with additional secondary faults concluded that this zone presents the highest potential of CO2 injection but without reaching the objective of 200 Mt with a reasonable number of wells. The simulation of the base scenario, carried out before the model refinement, showed that the overpressure above 0.1 MPa covers an area of 51,869 km2 in the Chaunoy formation, 1,000 years after the end of the injection, which corresponds to the whole West Paris Basin, whereas the CO2 plume extension remains small (524 km2). This overpressure causes brine flows at the domain boundaries and a local overpressure in the studied oil fields. Regarding the preliminary risk analysis of this project, the geochemical effects induced by the CO2 injection were studied by simulating the fluid-rock interactions with a coupled geochemical and fluid flow model in a domain limited to the storage complex. A one-way coupling of two models based on two domains fitting into each other was developed using dynamic boundary conditions. This approach succeeded to improve the simulation results of the pressure field and the CO2 plume as well as the geochemical behavior of the rock. These ones showed that the CO2 plume tends to stabilize thanks to the carbonation in calcite and dawsonite and no significant porosity change appears over 1,050 years. The CO2 mass balance per trapping type gives a CO2 carbonation rate of about 78% at 1,050 years that seemed to be excessive compared to the simulation study of other storage sites. Thus, an additional work dealing with both the kinetic data base and the textural models would be necessary in order to reduce the uncertainty of the injected CO2 mineralization

Turning-induced surface integrity for a fillet radius in a 316L austenitic stainless steel

International audienceTurning is a machining process extensively applied to produce revolution parts. Durability of these parts are known to depend on the turning process signature that is often referred as surface integrity. The surface integrity generated in a fillet radius has been barely studied in the literature so far, despite the well-known geometrical stress concentration factor of such singularities. Therefore this paper deals with the investigation of machining-induced surface integrity when turning a fillet radius in a 316L austenitic stainless steel. Different characterization methods are used for that purpose - SEM, EBSD, nanoindentation and X-Ray diffraction. It points out that the turning-induced consequences are not homogeneous along the machined profile. Residual stresses are strongly affected and microstructure is highly modified over a depth of 80 μm that leads to a mechanical properties gradient. It is evidenced that the average uncut chip thickness is the main governing parameter regarding surface integrity. It is also reported that deformation twins appear in the affected zone. It highlights that turning-induced microstructure evolution at a given depth is rather a consequence of severe plastic deformation at high strain rate than dynamic recrystallization