Modélisation du comportement dynamique non linéaire d'un système machine - outil - pièce lors d'une opération de fraisage

Les travaux de recherche menés dans cette thèse représentent une méthodologie de travail pour contribuer à l étude du comportement dynamique non linéaire du système M O P en fraisage. Cette méthodologie est orientée selon les objectifs principaux relatifs à cette thèse. En effet, la recherche bibliographique réalisée a permis de donner un aperçu sur les travaux existants dans ce cadre et d identifier les phénomènes vibratoires générés par la dynamique de coupe et les mécanismes d instabilité mis enjeu. En fait, le processus de coupe génère, selon le cas, deux formes de vibrations : les vibrations forcées et les vibrations auto entretenues. Dans une première approche, nous avons développé un modèle masse ressort (à deux degrés de liberté) du système O P pour étudier et analyser le comportement dynamique de la cellule élémentaire en fraisage. Ce modèle a permis d examiner l influence de la profondeur de passe sur la stabilité de la coupe. Cependant, ce modèle semble être insuffisant pour quantifier avec précision les vibrations en fraisage car les sources vibratoires générées par la dynamique de la machine ne peuvent être négligées. Dans une deuxième approche, nous avons modélisé le système globale Machine - Outil - Pièce. En effet, un modèle numérique basé sur la méthode de sous-structuration par éléments finis de l ensemble M O P a été développé. Cette modélisation permet de tenir compte de l effet de l inertie des différents éléments tournants de la fraiseuse, de la structure de la machine et de la forme de l outil. Nous avons ainsi réalisé des simulations du comportement dynamique global de l opération du fraisage. L influence de différents paramètres sur l effort de coupe tels que l avance, la profondeur de passe, les réponses dynamiques suivant les trois axes a été étudié. Cette étude a permis de conclure que ces paramètres sont fortement affectés par l usinage. Pour compléter cette étude numérique, une étude expérimentale a été menée afin d étudier l influence de différents paramètres de coupe. En effet, la méthodologie expérimentale développée a mis en évidence les paramètres les plus importants qui influent sur le comportement dynamique globale du système M O P. Cette étude expérimentale a nécessité le développement d un plan d expérience complet pour pouvoir définir les paramètres d entrées/sorties et organiser les essais à effectuer. L analyse des résultats a permis de détecter l influence de l avance et de la profondeur de passe sur le niveau des vibrations générées. Le bilan de ces résultats a mis le point sur les niveaux extrêmes des variables provoquant le niveau vibratoire le plus élevé. De plus une confrontation entre les résultats expérimentaux et numériques a été effectuée et a montré une bonne concordance.The research led in this thesis represents a methodology to contribute to the study of nonlinear dynamic behavior of the system M - O - P in milling. This methodology is directed according to the main objectives relative to this thesis. Indeed, the literature allows giving an overview of the existing work in this context and identifies the vibration phenomena generated by the dynamics of cutting mechanisms and the instability of the involved set cut. In fact, the cutting process generates, as applicable, two types of vibration: forced vibration and self excited vibration. In a first approach, we developed a model mass - spring (with two degrees of freedom) of the system O - P to study and analyze the dynamic behavior of the elementary machining cell in milling. This model was used to examine the influence of the depth of cut on the stability of the cut. However, this model appears to be insufficient to accurately quantify the vibrations in milling because the sources vibration generated by the dynamics of the machine cannot be neglected. In a second approach, we modeled the overall system Machine - Tool - Part; indeed, a numerical model based on the substructure method by finite element of the M - O - P was developed. This modeling takes into account the effect of inertia of the various rotating elements of the milling machine, the machine structure and shape of the tool. We have conducted simulations of the dynamic behavior of the overall operation of milling. The influence of different parameters on the cutting force such as advance, the depth of cut, and the dynamic responses along the three axes was investigated. This study concluded that these parameters are strongly affected by machining. To complement this numerical study, an experimental study was conducted to study the influence of different cutting parameters. Indeed, the experimental methodology developed has highlighted the most important parameters that influence the overall dynamic behavior of the system M - O - P. This experimental study required the development of an experimental complete to define the parameters of Input / Output and arrange to be tested. The analysis of the results allowed detecting the influence of feed and depth of cut on the level of vibration generated. The outcome of these results put the item on the extreme levels of variables causing the vibration level is higher. Over a confrontation between the experimental and numerical results was performed and showed a good agreement.CHATENAY MALABRY-Ecole centrale (920192301) / SudocSudocFranceF

Vibration Behavior of Composite Material with Two Overlapping Delaminations

International audienceThe paper presents an analysis of the vibration behavior of glass fiber reinforced composites with two overlapping delaminations. The effect of delamination length on the vibration parameters is studied. Throughout a series of vibration tests, the change of natural frequencies and modal damping due to delaminations is evaluated. A numerical simulation considering finite element analysis allows to predict the change of natural frequencies for a known damage size. Modal damping was established which evaluates the different energies dissipated in the material layers direction of the fiber reinforced composites. A comparison of the different results was performed. Next, strain energy of layers directions were established by a numerical analysis and discussed

Acoustic emission analysis of a laminate under a different loading rate

International audienceThe aim of this work is the identification with acoustic emission and the analysis of the damage mechanisms of a cross-laminated. A different laminate composed of epoxy resin and reinforced with glass fibers (GFRP), carbon fibers (CFRP) and hybrid fibers (HFRP) are considered. Static tests were performed, to study the influence of stacking sequence of laminates, the effect of thickness of 90° layers of fibers on behavior and the evolution of damage mechanisms. The specimens are solicited in buckling and traction tests. The acoustic signatures corresponding to the various damage mechanisms from material (matrix cracking, interfacial debonding...) are identified and their chronologies of appearances during the buckling and traction tests of the specimens are followed

Integration of topological modification within the modeling of multi-physics systems: Application to a Pogo-stick

International audienceThe present work tackles the modeling of multi-physics systems applying a topological approach while proceeding with a new methodology using a topological modification to the structure of systems. Then the comparison with the Magos' methodology is made. Their common ground is the use of connectivity within systems. The comparison and analysis of the different types of modeling show the importance of the topological methodology through the integration of the topological modification to the topological structure of a multi-physics system. In order to validate this methodology, the case of Pogo-stick is studied. The first step consists in generating a topological graph of the system. Then the connectivity step takes into account the contact with the ground. During the last step of this research; the MGS language (Modeling of General System) is used to model the system through equations. Finally, the results are compared to those obtained by MODELICA. Therefore, this proposed methodology may be generalized to model multi-physics systems that can be considered as a set of local elements

Topological Modeling of 2D Piezoelectric Truss Structure Using the MGS Language

International audienc

Fatigue behavior and damage analysis by the acoustic emission technique of cross-ply laminates under tensile loading

International audiencePurpose :The purpose of this paper is to study the mechanical behavior in fatigue tensile mode of different cross-ply laminates constituted of unidirectional carbon fibers, hybrid fibers and glass fibers in an epoxy matrix; and to identify and characterize the local damage in the laminated materials with the use of the acoustic emission (AE) technique.Design/methodology/approach : The tests in the fatigue mode permitted the determination of the effect of the stacking sequences, thickness of 90° oriented layers and reinforcement types on the fatigue mechanical behavior of the laminated materials. The damage investigation in those materials is reached with the analysis of AE signals collected from fatigue tensile tests.Findings :The results show the effects of reinforcement type, stacking sequences and thicknesses ratio of 90° and 0° layers on the mechanical behavior. A cluster analysis of AE data is achieved and the resulting clusters are correlated with the damage mechanism of specimens under loading tests.Originality/value :The analysis of AE signals collected from tensile tests of the fatigue failure load allows the damage investigation in different types of cross-ply laminates which are differentiated by the reinforcement type, stacking sequences and thicknesses ratio of 90° and 0° layers

Control vibration of a three-axis robot using the topological modeling

International audienc