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

Troubles neurologiques fonctionnels moteurs du membre inférieur, quelles pratiques de rééducation ? Une Scoping Review de ces 10 dernières années

This scoping review aimed to explore the current practices of physiotherapy for functional neurological disorders (FND) of the lower limb. FND is a neuropsychiatric disorder resulting in somatic impairment. Research is needed to establish the most effective treatment strategies for these disorder. Fourteen studies were included in the review and analyzed for their findings. The studies were identified through a systematic search of electronic databases, including PubMed, Embase, and Pubsy. The inclusion criteria were studies that reported on the use of physiotherapy interventions for FND of the lower limb. The studies were screened for relevance, and the data were extracted and analyzed using a thematic synthesis approach. The review highlighted the importance of a multidisciplinary approach to the treatment of these disorders, with emphasis on patient-centered care and individualized treatment plans. The use of therapeutic education, specific tests, motorretraining exercises with distraction and relaxation were identified as effective interventions for improving function in patients with FND of the lower limb. In conclusion, some practices seem to emerge from the care. Nevertheless, further research is needed to establish the most effective treatment strategies and to fill gaps in the literature.Cette revue de la portée vise à explorer les pratiques actuelles de kinésithérapie pour les troubles neurologiques fonctionnels (TNF) moteur du membre inférieur. Les TNF sont des troubles neuropsychiatriques entraînant une atteinte somatique. Leur traitement n’est pas clairement établis. Quatorze études ont été incluses dans la revue et analysées pour leurs résultats. Les études ont été identifiées grâce à une recherche systématique dans des bases de données électroniques, notamment PubMed, Embase et Pubsy. Les critères d'inclusion ont admis toutes études rapportant l'utilisation d'interventions de kinésithérapie pour les troubles neurologiques fonctionnels du membre inférieur. Les études ont été sélectionnées pour leur pertinence, et les données ont été extraites et analysées à l'aide d'une approche de synthèse thématique. L'examen a souligné l'importance d'une approche multidisciplinaire pour le traitement de ces troubles, en mettant l'accent sur les soins centrés sur le patient et les plans de traitement individualisés. L'utilisation de l'éducation thérapeutique, de tests spécifiques, d'exercices de rééducation motrice avec distraction et relaxation ont été identifiés comme des interventions efficaces pour améliorer la fonction chez les patients présentant des troubles neurologiques fonctionnels du membre inférieur. En conclusion, certaines pratiques semblent émerger du soin. Néanmoins, des recherches supplémentaires sont nécessaires pour établir les stratégies de traitement les plus efficaces et pour combler les lacunes dans la littérature

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

International audienc

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

International audienc

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

Fracture and atypical migration of an implantable central venous access device

International audienceDistal embolization of a fractured indwelling central catheter is a rare complication. The pinch-off syndrome (POS) should be known, prevented and early detected. We present a case in which further radiological exams were required to find the fragmented catheter with an atypical migration, requiring local surgery for removing. After chest and abdominal CT scan, neck X-ray, and heart echography, the catheter was found on the lower limbs X-ray on the internal side of right knee corresponding to a location of saphenous vein. Implanted catheters should be removed after completion of treatment and the integrity of the system should be monitored. To avoid POS, a catheter must be inserted into the subclavian vein as laterally as possible

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