Modelling of material cutting with a material microstructure-level (MML) model

In this research work a material microstructure-level cutting model (MML cutting model) is presented. The crystal plasticity theory is adopted for modeling the cutting of the titanium alloy Ti–6Al–4V in orthogonal case. In this model, the grains of the studied material are explicitly presented, and their orientation angles and slip system strength anisotropy are considered as the main source of the microstructure heterogeneity in the cutting material. To obtain the material degradation process, the continuum self-consistent intragranular damage model and discrete cohesive zone inter-granular damage model, were developed, wherein the zero thickness cohesive element is implemented to simulate the bond between grain interfaces. This model was validated by a comparison with compression tests from literature. Results demonstrate the possibility to capture the influence of the microstructure on the material removal in terms of chip formation. Particularly, it is demonstrated that the grain orientation angle plays an important role for the chip segmentation and its periodicity during the cutting process

On the selection of Johnson-Cook constitutive model parameters for Ti-6Al-4V using three types of numerical models of orthogonal cutting

Johnson-Cook constitutive model is still the most used model in metal cutting simulation, although several drawbacks reported in the literature. A high number of Johnson-Cook model parameters can be found in the literature for the same work material. One question that may arise is “What is the most suitable set of Johnson-Cook model parameters for a given material?”. The present paper puts in evidence some issues related with the selection of these parameters from the literature. In this contribution, two sets of Johnson-Cook model parameters for Ti-6A-4V are evaluated, using three types of metal cutting models. These models are based on three different formulations: Lagrangian, Arbitrary Eulerian-Lagrangian (ALE) and Couple Lagrangian-Eulerian (CEL). This evaluation is based on the comparison between measured and predicted chip geometry, chip compression ratio, forces, plastic deformation and temperature distributions

Modeling and Optimization of Cutting Parameters during Machining of Austenitic Stainless Steel AISI304 Using RSM and Desirability Approach

In the current paper, cutting parameters during turning of AISI 304 Austenitic Stainless Steel are studied and optimized using Response Surface Methodology (RSM) and the desirability approach. The cutting tool inserts used in this work were the CVD coated carbide. The cutting speed (vc), the feed rate (f) and the depth of cut (ap) were the main machining parameters considered in this study. The effects of these parameters on the surface roughness (Ra), cutting force (Fc), the specific cutting force (Kc), cutting power (Pc) and the Material Removal Rate (MRR) were analyzed by ANOVA analysis.The results showed that f is the most important parameter that influences Ra with a contribution of 89.69 %, while ap was identified as the most significant parameter (46.46%) influence the Fc followed by f (39.04%). Kc is more influenced by f (38.47%) followed by ap (16.43%) and Vc (7.89%). However, Pc is more influenced by Vc (39.32%) followed by ap (27.50%) and f (23.18%).The Quadratic mathematical models, obtained by the RSM, presenting the evolution of Ra, Fc, Kc and Pc based on (vc, f, and ap) were presented. A comparison between experimental and predicted values presents good agreements with the models found.Optimization of the machining parameters to achieve the maximum MRR and better Ra was carried out by a desirability function. The results showed that the optimal parameters for maximal MRR and best Ra were found as (vc = 350 m/min, f = 0.088 mm/rev, and ap = 0.9 mm)

Étude des perturbations thermiques induites par des hétérogénéités de contact à l'interface outil-copeau en usinage

Ce travail s’inscrit dans une démarche globale d’amélioration de la simulation des opérations d’usinage, et à une échelle plus locale, de la modélisation de la coupe des métaux. Il s’agit ici de remettre en question les conditions de « contact parfait » communément supposées à l’interface outil-copeau. Des essais de coupe orthogonale sont tout d’abord réalisés à sec sur un acier C45 avec des outils carbures revêtus TiN. Les zones de contact outil-copeau sont analysées par MEB-EDS afin de dissocier les parties « collantes » et glissantes du contact et d’évaluer la distribution d’éventuels dépôts. Un mécanisme de formation d’une résistance thermique de contact (RTC) est proposé suite aux faibles taux réels de contact extraits des cartes EDS. Une modélisation aux éléments finis est ensuite développée pour mettre en valeur l’impact de telles conditions thermiques de contact sur le procédé. Les efforts de coupe moyens, l’épaisseur du copeau généré et la longueur totale de contact apparaissent très peu sensibles à la RTC. Les grandeurs thermiques telles le flux de chaleur transmis à l’outil coupant, le champ de températures résultant et la continuité en température de part et d’autre de l’interface outil-copeau sont en revanche réellement affectées suivant son amplitude. On montre par ailleurs que la formation d’une résistance thermique de contact non négligeable à l’interface outil-copeau peut modifier fortement le partage de chaleur local par rapport à un contact supposé « parfait ». Ces aspects deviennent cruciaux lorsque l’on s’intéresse à des problèmes locaux comme l’usure outil où les grandeurs comme la température sont primordiales. L’existence d’une zone de contact hétérogène doit alors être prise en compte dans les simulations. Cette étude souligne encore le besoin d’introduire une dimension physique supplémentaire par des modèles de transfert de chaleur locaux afin d’améliorer la fiabilité des simulations d’usinage

Modélisation et simulation numérique de l'emboutissage d'un renfort tissé sec : Sensibilité de l'angle de cisaillement aux paramètres du procédé

Le présent travail a pour objectif de présenter une étude de sensibilité des modèles numériques réalisés avec le code ABAQUS, vis-à-vis de la variation des paramètres du procédé d'emboutissage, ainsi que l'effet d'orientation initiale du renfort, le type (coque ou membrane) et la taille du maillage. La simulation de la mise en forme est réalisée à l'échelle macroscopique en considérant le renfort comme un milieu continu. Cette approche continue s'appuie sur une loi de comportement hypoélastique qui a l'aptitude de suivre la rotation des fibres (directions d'anisotropie) au cours de la mise en forme. Cette loi de comportement est implémentée dans le code de calcul des éléments finis ABAQUS /explicit en utilisant une subroutine VUMAT

Modeling and optimization of tool wear and surface roughness in turning of austenitic stainless steel using response surface methodology

The wear of cutting tools remains a major obstacle. The effects of wear are not only antagonistic at the lifespan and productivity, but also harmful with the surface quality. The present work deals with some machinability studies on ?ank wear, surface roughness, and lifespan in ?nish turning of AISI304 stainless steel using multilayerTi(C,N)/Al2O3/TiN coated carbide inserts. The machining experiments are conducted based on the response surface methodology (RSM). Combined effects of three cutting parameters, namely cutting speed, feed rate and cutting time on the two performance outputs (i.e. VB and Ra), and combined effects of two cutting parameters, namely cutting speed and feed rate on lifespan (T), are explored employing the analysis of variance (ANOVA).The relationship between the variables and the technological parameters is determined using a quadratic regression model and optimal cutting conditions for each performance level are established. The results show that the flank wear is influenced principally by the cutting time and in the second level by the cutting speed. In addition, it is indicated that the cutting time is the dominant factor affecting workpiece surface roughness followed by feed rate, while lifespan is influenced by cutting speed

Hypoelastic, hyperelastic, discrete and semi-discrete approaches for textile composite reinforcement forming

International audienceThe clear multi-scale structure of composite textile reinforcements leads to develop continuous and discrete approaches for their forming simulations. In this paper two continuous modelling respectively based on a hypoelastic and hyperelastic constitutive model are presented. A discrete approach is also considered in which each yarn is modelled by shell finite elements and where the contact with friction and possible sliding between the yarns are taken into account. Finally the semi-discrete approach is presented in which the shell finite element interpolation involves continuity of the displacement field but where the internal virtual work is obtained as the sum of tension, in-plane shear and bending ones of all the woven unit cells within the element. The advantages and drawbacks of the different approaches are discussed

Stripping process modelling: interaction between a moving waterjet and coated target

International audienceThis paper deals with the numerical modelling of stripping process by a mono-jet moving tool. The example of aeronautic coating (polyurethane) deposit on an infinite homogeneous metal (A2024) was treated. The numerical computation was carried out using Dyna3D code. In order to study the jet-target interaction, we have used an eulerian description for the fluid (waterjet+air) and a lagrangian formulation for the target. The interaction between the two meshes is based on euler-lagrange coupling. The Hydrodynamic results show the importance of the jet flattening on the treated-coated target. It appears clearly that moving watertjet introduces, during decoating process, shear stresses causing coating removal by erosion mode. The latter has been simulated thanks to a failure criterion of lagrangian elements illustrating the coating removal under high velocity moving waterjet. This erosion is accentuated by waterjet stretching effects, which cause tearing of the coating. Consequently, discontinuous cracks at the median line of the coating imprint can be observed. These cracks can be privileged sites, which are traversed by speedy micro-jets accelerating the coating removal. Our results were demonstrated by experimental tests

EXPLORATION EXPERIMENTALE ET MODELISATION NUMERIQUE DES IMPACTS FLUIDIQUES (CONTRIBUTION A L'ETUDE DU DECAPAGE PAR JET D'EAU PURE HP)

PARIS-Arts et Métiers (751132303) / SudocCLERMONT FD-IFMA (630142301) / SudocSudocFranceF

Modelling of material cutting with a material microstructure-level (MML) model

In this research work a material microstructure-level cutting model (MML cutting model) is presented. The crystal plasticity theory is adopted for modeling the cutting of the titanium alloy Ti–6Al–4V in orthogonal case. In this model, the grains of the studied material are explicitly presented, and their orientation angles and slip system strength anisotropy are considered as the main source of the microstructure heterogeneity in the cutting material. To obtain the material degradation process, the continuum self-consistent intragranular damage model and discrete cohesive zone inter-granular damage model, were developed, wherein the zero thickness cohesive element is implemented to simulate the bond between grain interfaces. This model was validated by a comparison with compression tests from literature. Results demonstrate the possibility to capture the influence of the microstructure on the material removal in terms of chip formation. Particularly, it is demonstrated that the grain orientation angle plays an important role for the chip segmentation and its periodicity during the cutting process