Modélisation de l'étirage à froid de tubes par analyse éléments-finis

Le procédé d'étirage permet de fabriquer des tubes minces, en réduisant progressivement leur épaisseur ainsi que les diamètres intérieur et extérieur. Dans ce cadre, deux procédés d'étirage à froid sont étudiés avec deux matériaux, un acier austénitique (316LVM) et un acier cobalt (L605). Cette étude aborde différentes problématiques telles que le comportement élastoplastique d'un matériau, les contacts, les frottements et la convergence numérique. Des essais sur banc d'étirage sont réalisés pour enregistrer les efforts et les dimensions. Dans une première approche, des essais de traction quasistatique conduisent à appliquer une loi de comportement élastoplastique avec un écrouissage isotrope. Un modèle statique axisymétrique est utilisé dans les simulations. Finalement, après comparaison des résultats expérimentaux et numériques, cette étude souligne la nécessité d'une meilleure compréhension et modélisation du comportement du matériau, dans des conditions de sollicitations représentatives de celles rencontrées lors de l'étirage

Thermomechanical modelling of cold drawing processes of Co-Cr small diameter tubes

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Tube Drawing Process Modelling By A Finite Element Analysis

International audienceDrawing process is used in manufacturing thin-walled tubes, while reducing progressively their wall thickness and their inner and outer diameters. In this paper a stainless steel 316LVM is studied with one drawing process: hollow sinking. This study gets into different issues including elastoplastic behaviour, thermomechanical coupling, contacts, friction and numerical convergence. Experimental drawings are realized on a testing bench where forces, dimensional data and temperature are recorded. In a first approach, tensile tests lead us to use an elastoplastic constitutive equation with an isotropic hardening law. In simulations, an axisymetric steady-state thermomechanical model is used. Numerical results are compared with experimental results. Finally, in spite of some defaults, this study shows that finite element modelling is able to foresee accurately the thermomechanical behaviour of a tube during a drawing process. A better understanding and modelling of the thermomechanical behaviour of materials will improve the FEM simulation results

Détermination du coefficient de frottement par analyse inverse pour l'étirage de tube

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Tube Drawing Process Modelling By A Finite Element Analysis

International audienceDrawing process is used in manufacturing thin-walled tubes, while reducing progressively their wall thickness and their inner and outer diameters. In this paper a stainless steel 316LVM and a cobalt alloy L605 are studied with two drawing processes, hollow sinking and plug drawing. This study gets into different issues including elastoplastic behaviour, contacts, friction and numerical convergence. Experimental drawings are realized on a testing bench where forces and dimensional data are recorded. In a first approach, tensile tests lead up to apply an elastoplastic constitutive equation with an isotropic hardening law. In simulations, an axisymetric steady-state model, with numeric stabilization if needed, is used. Numerical results are compared with experimental results. Finally, in spite of some defaults, this study shows that finite element modelling is able to foresee accurately the behaviour of a tube during a drawing process. A better understanding and modelling of the mechanical behaviour of materials will improve the FEM simulation results

Thermomechanical modelling of cold drawing processes of small diameter tubes

International audienceTube cold drawing processes are used to reduce tube diameters and thicknesses, while pulling them through a conical converging die with or without inner plug. An accurate modelling of the material deformation, friction behaviour and thermal effects is required in order to well describe these processes. Finite element (FE) modelling has already been applied to wire drawing as well as tube drawing [1, 2, 3]. All of these works carry out mechanical studies but none of them justify the value of their friction coefficient. The aim of the present study is to model tube drawing with a thermomechanical finite element analysis. It deals with the cold hollow sinking (without inner plug) and the mandrel drawing of stainless steel 316LVM tubes of small diameters (typically from 1 to 10 mm). It details the method to obtain all required parameters. During the forming process, mechanical and thermal measurements are recorded. Load cells are placed between the die and the frame for the drawing force. A thermocouple is placed inside the tube and a pyrometer, fixed on the die exit, records the tube external temperature. When possible, simulation parameters are determined thanks to mechanical or thermal tests. The material properties implied in the process, such as the anisotropy and the rate-dependence are studied. Shear and tensile tests are performed to determine the 316 stainless steel mechanical behaviour and lead to apply an isotropic temperature-independent Johnson-Cook law. The emissivity and the convection of the tube are determined by thermal tests during experimental tests. An infrared camera placed in front of the shearing device is used to observe the temperature variation fields. As the strain rates are high and the experiments times are short, heat loss through conduction, convection, or radiation can be neglected in comparison to thermoplastic heating

Cold drawing of 316L stainless steel thin-walled tubes: experiments and finite element analysis

International audienceDrawing process of thin walled tubes used to fabricate catheters and stents for medical applications was studied. Medical use needs accurate dimensions and a smooth finish of the inner and outer surfaces. This paper deals with 316L stainless steel tubes which are manufactured by means of cold drawing with or without inner plug (mandrel drawing and hollow sinking, respectively). To improve the quality of the finish of the tubes, numerical modelling can be used. In this way, a thermomechanical study of the drawing process is proposed to determine experimentally the physical parameters. This study proposes to evaluate the different parameters of the constitutive equations, of the thermal and friction models using specific experimental tests or using an inverse analysis on the drawing process. These parameters are validated by analysing other tube drawings. Finally the importance of physical parameters fit on drawing limits is emphasised, using a Cockcroft-Latham failure criterion