Identification of debinding behaviours for 316L stainless steel feedstocks during thermal debinding stage

In this study, thermal debinding has been used under argon atmosphere by subjecting the feedstock to heating cycles. During the preparation of 316L stainless steel feedstock, binders are often added to increase the strength of the green body. These binders need to be removed prior to densification of the stainless steel components. This paper presents the experimental technique and the results of the study. The model prediction will compared with the experimental data

Expérimentation et simulation numérique du déliantage thermique et de la densification des composants obtenus par moulage par injection de poudres.

Thermal debinding is one of the most important steps In Powder Injection Moulding process. Thermogravimetric analyses (TGA) are employed to analyze the physics and kinetics of thermal debinding behaviour under argon atmosphere. The Kissinger and Ozawa method have been used to estimate the kinetic parameters from thermogravimetric experiments. To set up the numerical simulations of thermal debinding stage using finite element method, a coupled mathematical has been developed. The basic steps of the proposed model consist to solve the following sequences of coupled problems: themal degradation of binder coupled with heat transfer and deformation phenomena by finite element method using Comsol Multiphysics software.In the second part of this thesis, sintering behaviour of tungsten powders injection moulded component, under pure hydrogen atmosphere at temperature up to 1700°C. The experimental tests are used to determine the material parameters in the parameters in the viscoplastic constitutive law, which is incorporated with the identified parameters in order to simulate the final shrinkages and densities of tungsten injection moulded components during the sintering process. Comparison between the numerical simulations results and experimental ones, in term of shrinkages and sintered densities, shows a good agreement.L'étape de déliantage est une étape importante et parfois critique pour le procédé Moulage par Injection des Poudres. A cet effet, des analyses thermogravimétriques (TGA) ont été réalisées pour bien comprendre les mécanismes du déliantage thermique sous atmosphère imposée (Argon). Les méthodes de Kissinger et Ozawa ont été utilisées, en se basant sur les résultats des analyses thermogravimétriques, afin d’estimer les paramètres cinétiques nécessaires pour la simulation numérique, notre modèle se propose de décrire les phénomènes physiques liés à la dégradation du polymère, le transfert de chaleur de la déformation du composant pendant le déliantage thermique.La deuxième partie de la thèse est dédiée à la compréhension des mécanismes et du comportement du fritage des composants en tungstène sous une atmosphère d’hydrogène jusqu’à une température de 1 700°C. Des appareils expérimentaux, ont été mis en place afin de constituer une base de données physiques nécessaire pour l’identification des différents paramètres. L’identification de l’ensemble des lois de comportement a été réalisée en prenant en compte les spécificités physiques des poudres utilisées. Un modèle de comportement de type thermo élasto-viscoplastique est formulé pour représenter la loi de densification par diffusion solide, puis appliqué pour les différentes tailles de poudres de tungstène. La dernière étape consiste à valider des simulations numériques avec ABAQUS pour une meilleure détermination des densités et des retraits finaux des composants injectés

Solvent debinding process in powder injection molding : experiments and numerical simulations

International audiencePowder Injection Molding (PIM) is a technology in which thermoplastic polymeric materials with a high content of metallic powders are molded in a required shape. In this paper, solvent debinding for copper green components shaped by powder injection molding has been investigated. All the solvent debinding process tests have been carried out in water at various temperatures [40 to 60°C]. The distribution of the remaining soluble binder content inside the specimen has been described by using second Fick’s diffusion law. Numerical simulations based on the finite element method have been carried out for validation through determination of the remaining soluble binder content at different debinding times. Results also showed that solvent temperature and component thickness played a very important role in the water debinding process. A properly adapted model describing the required debinding time, for components with different thicknesses at different temperatures, has been established. The proposed numerical simulation model provides improved monitoring possibilities for solvent debinding process particularly to extract binder from the complicated molded components

Solvent debinding process in powder injection molding : polymers and loaded polymers with nano particles

International audienceSolvent debinding process in powder injection molding : polymers and loaded polymers with nano particle

EXPERIMENTAL VERIFICATION OF THE NEW MODELS APPLIED TO GLASS FIBRE REINFORCED CONCRETE (GFRC) CONFINED WITH GLASS FIBRE REINFORCED POLYMER (GFRP) COMPOSITES

External confinement by the GFRP composites offers an actual process for retrofitting glass fibre reinforced concrete columns (GFRC) subject to static or seismic loads. This paper presents an experimental investigation and analytical modelling of the axial compression of confined circular concrete columns of different strengths (8.5, 16, and 25 MPa). Furthermore, the columns contain different percentages of glass fibres (0.3 to 1.2%), and their confinement is given by GFRP composites of various thicknesses (0.4 to 2.4 mm). The uniaxial compression test on these specimens reveals that the glass fibre percentage and the thickness of the GFRP play a vital role in improving the load-deformation behaviour and crack propagation. Whatever the concrete strength, the ultimate axial strain and stress predicted using the suggested confinement model almost agrees with the available experimental results

Investigations on thermal debinding process for fine 316L stainless steel feedstocks and identification of kinetic parameters from coupling experiments and finite element simulations

International audienceThermal debinding is one of the most important steps in powder injection moulding process. Thermogravimetric analysis (TGA) was employed to analyze thermal debinding behaviour under argon atmosphere. Thermal debinding kineticswith different heating rates have been compared using 316L stainless steel feedstocks loaded typically at 60, 62, 64 and 66 vol.% for fine metallic powders D50=3.4 μm. The Kissinger and Ozawa methods have been used to estimate the kinetic parameters fromthermogravimetric experiments. To set up the numerical simulations of thermal debinding stage using finite element methods, a coupled mathematical model for mass diffusion and heat transfer in deformable porous media have been developed. The basic steps of the proposed model consist of solving the following coupled problems: thermal degradation of binder coupledwith heat transfer and deformation phenomena by finite element methods using Comsol Multiphysics® software. The obtained numerical simulation results are in proper agreement with experimental data. The proposed numerical simulations allowthe determination of remaining binder distribution, temperature distribution and deformation fields in the component during the whole thermal debinding process at any tim

Experimental investigation on the mechanical behavior of concrete reinforced with Alfa plant fibers

Currently, the reinforcement of ordinary concrete with synthetic fibers poses ecological problems because the manufacturing process of these products is very polluting. Plant fiber composites are a new challenge for environmental protection. The present article aims to investigate the mechanical behavior of concrete reinforced with natural fibers, called alfa fibers. Compression and three-point bending tests have been performed on cubic and prismatic samples, respectively. Different fiber lengths (2.5, 5, and 8 cm) and content (0.6, 1.2, and 1.8%by volume) of alfa fibers have been used to examine their influence on the mechanical behavior of the fiber-reinforced concrete. The obtained results show that for a volume content of 1.2% of plant fibers of 5 cm length, the tensile strength of the reinforced concrete increases up to 54.41% compared to the ordinary concrete (BT). However, for content of 1.8% of fibers with 8 cm length, both the compressive and tensile strength of the reinforced concrete decrease slightly. At this level, an excess of both fiber content and their length produces the formation of voids within concrete. Moreover, such an excess made the hydration reaction slower. It is worth noticing that the orientation of fibers also plays a significant role in the nucleation and propagation of microcracks. The fibers arranged both horizontally and obliquely are more resistant to microcracking than those oriented in the loading direction

Investigation on machining of a Ti–6Al–4V alloy using FEM simulation and experimental analysis

International audienceTitanium alloys have been attracting from the more industries, especially, industry aerospace due to their very important high strength to weight ratio. Furthermore, they were classified as difficult to machine materials due to low tool life in machiningprocesses. In this study, a FE model has been developed to simulate the turning stage of Ti–6Al–4V alloy. A 3D model with thermo-mechanical coupling has been proposed to study the influence of cutting parameters and also lubrication on the performance ofcutting tools. The constants of the Johnson–Cook constitutive model of Ti–6Al–4V alloy were identified using inverse analysis based on the process parameters of the orthogonal cutting. The predictive FE model has been validated based on an orthogonal cutting test. The investigations indicated that this approach estimates the resultantcutting forces with low prediction errors. Indeed, the predicted forces showed good agreement with the experimental data, with minimum and maximum error magnitudes of 2.8 and 8.7% for cutting force, and 1.3 and 6.8% for feed force, respectively

Finite element modeling and numerical simulation of sintered tungsten components under hydrogen atmosphere

International audiencePowder injection molding (PIM) is a suitable technology for manufacturing of complex shapes with tungsten powders and has a great potential in many applications. Sintering is one of the most important steps in Powder Injection Molding process. The sintering behaviour of tungsten injection moulded components, under pure hydrogen atmosphere at temperature up to 1700°C using fine 0.4μm and coarse powders 7.0 μm, is investigated by means of the beam bending and dilatometric tests in the Setaramcopyright, serif analyser. To simulate the shrinkage and shape distortion of tungsten injection moulded components during the sintering process using finite element methods, viscoplastic constitutive law is implemented in ABAQUS software as user subroutine UMAT and incorporated with the identified parameters. Comparison between the numerical simulations results and experimental ones, in term of shrinkages and sintered densities, shows good agreement between the two