Experimental and numerical study of laser-assisted machining of Ti6Al4V titanium alloy

Laser-assisted machining combines several experimental parameters such as cutting speed, feed rate, depth of cut, laser power and distance between tool rake face and the laser beam axis. The optimization of these parameters is necessary to ensure the efficiency of assistance and to increase productivity. This paper focuses on the understanding of the physical phenomena during laser-assisted machining, and on optimising this process. This contribution is based on an experimental and a numerical study. The experimentalpart highlights the effects of the laser power as well as the distance between the tool rake face and the axis of the laser beam. As for the numerical part, it was performed on the ABAQUS/Explicit software. The proposed model improves the understanding of the physical phenomena of chip formation and the cutting force reduction when machining with laser assistance. In addition, this model allows a better optimization of laser and cutting parameters.Numerical findings generally corroborate experimental results and can lead to some other information difficult to catch experimentally. The main contention in the paper is that the distance between the axis of the laser beam and the tool rake face is the most important parameter that controls the reduction of the cutting force. This cutting force reduction can exceed 50%

Multistep hybrid approach applied to material removal operation using cutting tool

Cutting processes are widely used in different industries to cut different engineering parts. Usually the optimization of these processes is made by experimental or numerical simulations but the major inconvenience of those methods is the cost and the time needed. For all these reasons, in manufacturing industry, a highly interest in analytical methods are usually researched because there are very practice to use but those methods don’t take into account all the aspects of the contact between the work material and the tool. In particular ploughing and spring back are usually not considered, what is pertinent for small cutting radius but not for bigger ones (used tools). In this paper en hybrid approach is presented. Both analytical and numerical approaches are used in order to model and understand physic during removal processes. In particular a multi-steps model for orthogonal cutting has been developed in order to study the influence of the cumulated strain and temperature induced by the different steps on the residual stresses. The effect of tool edge radius and heat generated by flank friction on the predicted stress profile is analytically modelled. In fact, in the case of most of industrial processes, like turning, milling, grinding, the cutting tool is in contact with a part of material that was the finished piece in the previous step Commercial finite element software ABAQUS with its Explicit and Implicit modules was used. Computed Numerical predicted stress fields are compared against measured residual stresses obtained by X-Ray diffraction. Moreover, in order to take into account all the physics in the tool-work material interface, spring-back simulation was performed using both ABAQUS Explicit and ABAQUS Implicit

Simulation numérique de la coupe orthogonale Influence de paramètres numériques

International audienceThe study of material removal local mechanisms is relevant in all machining processes. Nevertheless, the complexity of phenomena encountered within this framework, often limits approaches to a configuration known as « orthogonal cutting ». Experimental and analytical methods developed for these studies are often associated with numerical simulations using the finite element method. The aim of this paper is to focus on the influence of numerical parameters related to this method. Some problems linked to the mesh are highlighted. The density of the mesh is shown to be the most influencing parameter on the results due to localisation phenomena.L'étude des mécanismes locaux d'enlèvement de matière est primordiale dans tous les problèmes de mise en forme par usinage. Néanmoins, la complexité des phénomènes rencontrés dans le cadre de la coupe, limite souvent les approches à une configuration dite de « coupe orthogonale ». Les méthodes expérimentales et analytiques développées pour ces études sont de plus en plus associées à des simulations numériques utilisant la méthode des éléments finis. L'objectif de cet article est de s'intéresser à l'influence de paramètres purement numériques, relatifs à l'utilisation de cette méthode. Des problèmes liés au maillage sont notamment mis en évidence. La densité de ce dernier apparaît comme le paramètre le plus influant sur les résultats obtenus, avec l'apparition de phénomènes de localisation

Contribution à l'étude de la physique de l'interface meule-pièce dans le cadre de la rectification conventionnelle et à grande vitesse

Les premières études scientifiques du processus de rectification ont très probablement débuté en 1890, époque où les premières meules synthétiques ont été fabriquées. Depuis, seuls quelques modèles géométriques locaux (1943) ont permis de prédire les avantages de la grande vitesse, mais pas de comprendre la physique de l'abrasion. Depuis une décennie, les professionnels de la rectification ont pu construire les premières machines spécialement dédiées à la grande vitesse (RGV). On constate que l'utilisation de telle machine repose fortement sur l'expérience notamment pour déterminer les zones de bon fonctionnement. La compréhension de la physique de coupe semble alors être une étape incontournable. Le travail de thèse débute par une synthèse faisant état de l'art des différents travaux effectués ces cinquante dernières années dans le domaine de la rectification. Des méthodes pour cerner la physique de l'abrasion sont ensuite présentées au travers d'investigations expérimentales. A cet effet, une manipulation originale sur une rectifieuse munie d'une meule à grain unique a été entièrement dimensionnée et finalisée au LTDS. Les résultats ont permis de mieux cerner les différentes phases de la coupe et de définir comme en tournage, la notion de copeau minimum à léchelle du grain abrasif. Une méthode de calcul de l'énergie spécifique d'abrasion est ensuite développée. Par ailleurs, des moyens originaux de visualisation par des techniques de "multi-expositions" ont permis de voir des copeaux dans l'interface et d'en déduire la vitesse. Enfin, un modèle thermomécanique par éléments finis du processus a permis de comprendre et d'expliquer qualitativement les mécanismes d'apparition des contraintes résiduelles. Cette étude est importante car le comportement et la durée de vie de la pièce en fonctionnement dépend fortement du signe des contraires.The scientific study of the grinding process have begun in the early 1890 probably when the first synthetic grinding process existed since 1943 but it not gives any information about the abrasion physics comprehension. Now high speed grinders are built and the users are yield to reason that in such process the determination of the good parameters is essentially based on each one experience. In this case it seems important to grasp the cutting physic in the grinding work area. This thesis begins with a large state of the art of the grinding process. Further more some experimental investigations to sorround the abrasion physic are presented. With this end in view an original high speed crash test using a grinding wheel fitted out with a single abrasive grain is presented and allowed to understand the way the chip is formed. Some other experiments are developed like chips visualization in order to compute their velocity. Finally a finite element modelling is realised and allowed to explain the residual stress appearance mechanism and to compute them. This last study is really important because the workpieces behaviours in their mechanisms hardly depend on the residual stress distribution.ST ETIENNE-ENISE (422182303) / SudocLYON-Ecole Centrale (690812301) / SudocSudocFranceF

The use of numerical simulations to improve a new analytical chip formation model

In this paper, an analytical approach is proposed to model chip formation in the case of turning process. Numerical simulations of chip genesis are performed in order to fit efficiently the proposed analy- tical model. In particular, cutting edge radius influence, temperature and internal stresses distribution are studied using finite element modelling. Numerical model setting is made with experimental and literature data using forces and chip thickness

Analytical Model of Chip Formation in Case of Orthogonal Cutting Processes

International audienc

Simulation numérique de la coupe orthogonale Influence de paramètres numériques

International audienceThe study of material removal local mechanisms is relevant in all machining processes. Nevertheless, the complexity of phenomena encountered within this framework, often limits approaches to a configuration known as « orthogonal cutting ». Experimental and analytical methods developed for these studies are often associated with numerical simulations using the finite element method. The aim of this paper is to focus on the influence of numerical parameters related to this method. Some problems linked to the mesh are highlighted. The density of the mesh is shown to be the most influencing parameter on the results due to localisation phenomena.L'étude des mécanismes locaux d'enlèvement de matière est primordiale dans tous les problèmes de mise en forme par usinage. Néanmoins, la complexité des phénomènes rencontrés dans le cadre de la coupe, limite souvent les approches à une configuration dite de « coupe orthogonale ». Les méthodes expérimentales et analytiques développées pour ces études sont de plus en plus associées à des simulations numériques utilisant la méthode des éléments finis. L'objectif de cet article est de s'intéresser à l'influence de paramètres purement numériques, relatifs à l'utilisation de cette méthode. Des problèmes liés au maillage sont notamment mis en évidence. La densité de ce dernier apparaît comme le paramètre le plus influant sur les résultats obtenus, avec l'apparition de phénomènes de localisation

ON NUMERICAL STRATEGY FOR TOOL WEAR MODELLING DURING AISI 4140 CUTTING

International audienceThe quality of machined products is strongly related to the machining conditions especially the tool wear evolution. The latter is among the most important problems encountered by manufacturers. In fact, the complexity of dealing with tool wear is due to the diversity of its origins (abrasion, diffusion, adhesion…) and the limits of models to predict it.For that, the majority of studies were based on experimental works to find laws linking tool wear to several cutting conditions [1, 2]. These estimations are limited to specific cutting conditions far from the industrial context. Some researchers resort to Finite Element (FE) Method to simulate cutting tool wear since it can help to investigate it finely than via experiment’s procedure [3, 4].The aim of this study is to develop a numerical model to simulate cutting tool wear via the FE software ABAQUS®. It is focused on the modeling of the machining of AISI 4140 steel by an uncoated tungsten carbide tool in an orthogonal cutting configuration.A multi-part model is developed to simulate tool wear in orthogonal cutting machining of AISI 4140 steel by an uncoated tungsten carbide tool. A new procedure helping to develop tool wear is implemented via Archard Law. The simulation results are validated by experimental tests

A New Procedure to Increase the Orthogonal Cutting Machining Time Simulated

International audienceSurface integrity is extremely affected by manufacturing processes conditions especially the evolution of cutting tool performance. Many researchers, in the domain of material machining, focused their works on the elaboration of models predicting tool wear combining both numerical and experimental approaches. Most of published numerical cutting models simulate the chip formation for a few micro to millisecond time periods. For that, all corresponding experimental tests, needed for the model validation, are usually carried-out in special time conditions which not reflecting industrial situations. Indeed, the latters are characterized by tool wear whose evolution can affect extremely cutting force levels and the final workpiece integrity. In this context, the main purpose of the proposed research work is to develop a FEM model, based on the commercial code ABAQUS, to simulate wear phenomenon of tool insert in the case of orthogonal cutting operation. The present research work is based on a lagrangian approach including an explicit step with the cutting model simulating the chip formation and an Implicit step reproducing the equivalent thermo-mechanical loading applied on the tool. An energetic based wear criterion (EBWC) is integrated in the model to simulate tool wear. Moreover experimentations are carried out to put out wear phenomenon and results are used to validate numerical simulations. They permit to quantify the energy dissipated by friction, which is at the base of the elaboration of the EBWC

Enhanced Photocatalytic Kinetics Using HDTMA Coated TiO₂-Smectite Composite for the Oxidation of Diclofenac under Solar Light

Slow kinetics is one of the capital issues of photocatalytic technology because of its heterogeneous nature, which involves multi-step processes. Herein, we show that the simple modification of the sol-gel-based TiO2-smectite composite by hexadecyltrimethylammonium bromide (HDTMA) significantly boosts adsorption and photocatalytic efficient sol-gel-based light towards the removal of diclofenac from water. Three photocatalysts were prepared, including TiO2, TiO2-smectite, and HDTMA-TiO2-smectite. The materials were characterized to understand the surface interaction and crystal characteristics. In terms of photoactivity, it was found that the addition of HDTMA to TiO2-smectite improved the removal rate by twice. HDTMA changes the functional groups to TiO2-smectite composite allowing enhanced adsorption and photoactivity through the so-called Adsorb and Shuttle process. The recycling tests show that HDTMA-TiO2-smectite can be used up to four times with good performance. This modification approach could intensify the removal of pollutants from water instead of using complicated and costly techniques