Nathalie Boudeau

Nathalie Boudeau
Institut FEMTO-ST | FEMTO ST · Department of Applied Mechanics

Professor

About

66
Publications
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450
Citations

Publications

Publications (66)
Article
Full-text available
During tube hydroforming process, the friction conditions between the tube and the die have a great importance on the material plastic flow and the distribution of residual stresses of the final component. Indeed, a three-dimensional finite element model of a tube hydroforming process in the case of square section die has been performed, using dyna...
Article
Full-text available
Metal forming operations are optimized by using finite element simulations. The numerical results are strongly dependent on the material data and the friction conditions. The present paper focuses on the tube hydroforming process and methods, developed by the authors, for the evaluation, the closest to the process conditions, of the hardening curve...
Article
Full-text available
The mechanical behavior of zinc alloys drastically depends on strain rate and temperature, which are not constant during forming processes. During the production of zinc sheets, the slight variations of the industrial equipment parameters induce different local thermomechanical conditions. These variations could be stemming from a non-homogeneous c...
Preprint
Full-text available
__________________________________________________ This paper focuses on the importance of taking into account the acceptable whitening limit of the protective coating of metals after forming processes. Coating aspects are essential to validate final products, especially if the coating has a design feature. The material studied is a standard zinc a...
Article
Full-text available
Zinc alloys are used in a wide range of application such as electronics, automotive and building construction. Their various shapes are generally obtained by metal forming operation such as stamping. Therefore, it is important to characterize the material with adequate characterization tests. Sheet Bulging Test (SBT) is well recognized in the metal...
Article
Full-text available
It is now well recognized that the material data obtained from a tensile test is less appropriate than those from a Tube Bulging Test (TBT) for a finite element simulation of tube hydroforming. However, the manufacturers still use classical data (often tensile test data) for designing metal operations due to the lack of standard for the TBT and a m...
Conference Paper
Full-text available
Zinc alloys are used in a wide range of application such as electronics, automotive and building construction. Their various shapes are generally obtained by metal forming operation such as stamping. Therefore, it is important to characterize the material with adequate characterization tests. Sheet Bulging Test (SBT) is well recognized in the metal...
Article
Full-text available
Zinc alloys are used in a wide range of application such as electronics, automotive and building construction. Their various shapes are generally obtained by metal forming operation such as stamping. Therefore, it is important to characterize the material with adequate characterization tests. Sheet Bulging Test is well recognized in the metal formi...
Article
Full-text available
It is generally known that the contact between tube and die, in the case of tube hydroforming process, leads to the appearance of friction effects. In this context, there are many different models for representing friction and many different tests to evaluate it. In the present paper, the pin-on-disk test has been used and the theoretical model of...
Article
Full-text available
Friction conditions are very critical in metal forming because they can lead to important thinning in the final manufactured product. The value of the friction coefficient is then of particular importance for performing predictive finite element (FE) simulation of forming operations. Classically, numerical simulations are run with values of the fri...
Article
Full-text available
This paper presents an experimental study on corner filling in the tube hydroforming process. A single-step tube hydroforming process was retained based on pure expansion hydroforming with the conjunction of only internal pressure loading. Several hydroforming experiments were performed with differently shaped dies, such as a square, a rectangular,...
Research
During tube hydroforming process, the friction conditions between the tube and the die have an importance on the thickness distribution in the final conponement: But it is difficult to characterize the friction coefficient conditions. Then it’s necessary to have a good evaluation of the friction coefficient for running predictive numerical simulati...
Conference Paper
Full-text available
During tube hydroforming process, the friction conditions between the tube and the die have an importance on the thickness distribution in the final conponement: But it is difficult to characterize the friction coefficient conditions. Then it's necessary to have a good evaluation of the friction coefficient for running predictive numerical simulati...
Article
Full-text available
The friction conditions are responsible of the thickness distribution in a part realized by tube hydroforming. Then it is essential to have a good evaluation of the friction coefficient for running predictive finite element simulations. The tube expansion in a square die is one of tests proposed for the friction evaluation. In the literature, sever...
Conference Paper
Full-text available
The effect of the friction coefficient in the strain path of hydroformed tube is discussed in this paper. A finite element simulation with the LS-DYNA/Explicit software has been performed and experiments have been carried out. The localized thinning can be related to necking and then, the use of the Forming Limit Curve (FLC) and the analysis of the...
Article
Full-text available
A focus on the effect of friction condition on tube hydroforming during corner filling in a square section die is proposed. Three approaches have been developed: an analytical model from the literature has been programmed, finite element simulations have been conducted and experiments have been carried out. Effect of friction coefficient on the thi...
Article
A complete analytical model combined with a very simple experimental procedure is proposed. It permits the post-processing of experimental measures to obtain the stress–strain curve for tubes very quickly and well adapted for industrial use. The quality of the results is proved by comparison with experimental measures and finite element results. An...
Article
Composite stems obtained by injection moulding of polyetheretherketone reinforced with carbon fibres (CF/PEEK) can concurrence metallic ones in total hip replacement. By the combination of process simulations and structural analysis, different compositions of CF/PEEK and injection conditions are explored. The resulting implants are compared to the...
Article
The paper is focused on a sensitivity analysis developed to study the relevance of experimental hardening curves obtained from tube bulging test to quantify the influence and the contribution of experimental uncertainties on the response variability. The experiments are based on “online” measurements of the internal pressure and the bulge height. A...
Conference Paper
The paper focuses on the miniaturization of the bulging test for material characterization of micro tubes. For the design of the experimental device, numerical simulations are conducted first. Even if no scale effect is taken into account in material modeling, numerical results give some information before designing the set-up and performing experi...
Article
To perform pertinent numerical simulations of tube hydroforming process, it has been demonstrated that material data obtained from tube bulging test were more suitable than the classical tensile test. Theoretical developments based on a novel geometrical modeling have led to an analytical evaluation of the strain and stress states all over the bulg...
Article
Full-text available
The paper is focused on the determination of mechanical characteristics for metallic materials shaped like tubes as used in tube hydroforming process. First, a procedure is described to carry out experimental tube bulging tests. It permits to identify a law linking the internal pressure to the bulge height. Second, based on this law and an original...
Article
This paper is focused on the determination of mechanical characteristics for metallic materials shaped like tubes [1,2,3] as used in hydroforming process. Like for other processes (forging, deep-drawing), specific laboratory tests can be required for material characterization. For tube hydroforming, it has been found that tube bulging test is more...
Article
This paper is focused on the determination of mechanics characteristics for tubular materials, using tube bulge process. A comparative study is made between two different models: theoretical model and finite element analysis. The theoretical model is completely developed, based first on a geometrical analysis of the tube profile during bulging, whi...
Article
Cet article s'intéresse à la détermination des propriétés mécaniques de matériaux sous forme de tubes par l'utilisation du procédé de gonflement.. Une étude comparative est réalisée entre deux modèles : une analyse théorique et un modèle par éléments finis. Le modèle théorique se base sur une analyse géométrique du profil du tube au cours du gonfle...
Article
A measure of powder layer heterogeneity has been proposed. It has been tested on the layers realized by different deposition techniques. Good correspondence of the actual measure to the subjective layer quality estimation has been shown. The influence of the laser scanning strategy on the quality of sintered structure has been examined. It is shown...
Article
A phenomenological TRIP model is proposed. It has been developed especially for industrial numerical simulations combining forming, springback, assembly and crash modelling. After comparison with micromechanical model of the literature its performances are illustrated by modelling the different stages of a U-channel composing a crash absorber. The...
Article
Full-text available
The paper first describes experiments and modeling concerning the identification of material behavior for high strength steels with phase transformations associated to plastic deformation. The experiments consist of tensile and bulging tests carried out on 316L stainless steels and TRIP 700 steels used in automotive industry. These experiments have...
Article
Full-text available
Within the framework of an European project concerning hydrogen storage, one analyze the way to manufacture high pressure tanks (700bars) for hydrogen storage, intended to be embarked for using in motor vehicles. These tanks consist of a metallic liner, which ensure a barrier role compared to the hydrogen atoms as well as a part of the mechanical r...
Article
Full-text available
Résumé : Le SLS, le Frittage Sélective par Laser, est un procédé de fabrication par apports successifs de matière. Initialement développé pour le prototypage rapide, il est actuellement testé par de nombreux moulistes en vue de son intégration dans la chaîne de production des moules. Cette technologie est séduisante car elles permettrait de réduire...
Article
The paper describes the experimental procedures carried out in order to investigate the rheological properties of carbon fiber reinforced polyetheretherketone (PEEK) and the mechanical properties of injection-molded parts from this material. Four test nozzles have been designed for the investigation of the rheological properties of PEEK. The nozzle...
Article
The paper describes a model and an inverse identification procedure for the material behaviour of new austenitic stainless steels used for car body panels, exhibiting transformation induced plasticity effects. The modelling is based on a phenomenological macroscopic approach and describes well the evolution of martensitic phase during deformation....
Article
New materials are appearing for sheet metal components. Their use in automotive industry require careful analysis of the influence of initial and induced properties on the formability and risks of failure during the process. The proposed approach is based on experimental investigations, mechanical modelling and FE simulations to analyse the effects...
Article
Bursting is predicted using a 3D-necking criterion based on local instability analysis. First, forming limit diagram (FLD) are built to validate the approach and the influence of material parameters is illustrated. Secondly, the criterion is implemented in a finite element code devoted to the simulation of hydroforming processes. Bursting predictio...
Article
Necking and bursting are current defects that appear and limit the flange and tube hydroforming processes. The linear stability analysis has been extended to 3D stress states in order to detect these defects during hydroforming processes. Numerical predictions are compared with experiments to illustrate the validity of the approach. In addition, th...
Article
Necking is a phenomenon limiting sheet metal-forming processes. The linearised perturbation technique is presented and adapted to various cases of yield criteria, damage models and 2D/3D stress states. Some aspects about calculations are given. Finally two applications of these works are shown. The first one validates the theory by establishing For...
Article
The necking of sheet metal is a main problem in forming processes that causes unacceptable thickness decreasing and leads to stop the process. There is a large amount of literature and research papers in this field. But the remaining problems to solve are the applicability and the accuracy of the methods for determining forming limits for various s...
Article
The paper deals with the influence of microstructural material aspects on the localized necking in sheet metal forming. The approach developed accounts for various microstructural material aspects as crystallographic slip, work hardening at microstructural level and lattice rotation which induces the texture evolution. The analyses are performed us...
Article
The chapter illustrates that the increasing of the void volume fraction in the case of sheet metal forming cannot be considered as a sufficient parameter for indicating necking. The linear perturbation technique adapted to the post-processing of finite element results is a real interesting tool as it allows detecting the necking zones. The critical...
Article
We propose a method based on the linear perturbation technique to predict the localized necking phenomenon in post-processing of finite element results for the simulation of deep-drawing processes. Numerous numerical results compared to experimental ones show the validity of such an approach. Numerical investigations have been performed to demonstr...
Article
The sheet necking prediction from FE simulations of sheet metal forming is in many cases based on using forming limit diagrams. An interesting alternative is presented in the paper based on the use of the linear stability analysis to treat the necking problem from FE results. The main advantage of the proposed approach is the possibility to take in...
Article
Necking in sheet metal forming is analyzed in the context of finite element simulation of 3-D sheet metal processes using shell elements. The possibilities and application fields of three different approaches that consider geometrical imperfections, material imperfections or the stability of the boundary value problem are analyzed. The material beh...
Article
Optimizing productivity, parts quality, reducing production costs are objectives that companies must perpetually satisfy to remain competitive. An efficient solution, but complex to implement, consists in modifying completely the manufacturing process. That is the goal of these research works : it consists in manufacturing micro-electronic componen...

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